Enforce new linting rules: errname, errorlint, lll, stylecheck (#32)

2022-11-09 11:21:11 +07:00 · 2022-11-09 11:21:11 +07:00 · 482dd095a6
commit 482dd095a6
parent ec08a5a918
16 changed files with 891 additions and 336 deletions
--- a/.golangci.yml
+++ b/.golangci.yml
@ -0,0 +1,9 @@
+linters:
+  enable:
+    - errname
+    - errorlint
+    - lll
+    - stylecheck
+linters-settings:
+  lll:
+    tab-width: 4
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@ -1,7 +1,72 @@
 # Contributing

-## Styleguides
+## Development guidelines

- Use default `goimports` for code formatting.
- Use default `golint`, `golangci-lint` and `go vet` for linting.
- Do not use boolean flag in function arguments.
+### Formatter
+
+We use `golangci-lint` to validate the code formatting. Make sure to have your code formatted before opening pull requests.
+
+### Line length limit
+
+Every code line should not exceed 80 characters when possible, but the hard limit is at 120 characters. Lines with documentation have an exception with the hard limit at 80 characters. A tab is treated as 4 spaces. It is recommended to set ruler guide at 80 and 120 characters on your editor.
+
+### Wrapping long struct initialization
+
+If the struct initialization is too long for the 80 character limit, wrap the initialization by assigning each field on its own line and end the initialization on its own line.
+
+**WRONG**
+
+```go
+a := User{
+    Firstname: "John", Lastname: "Doe",
+}
+
+a := User{
+    Firstname: "John",
+    Lastname:  "Doe"}
+
+a := User{Firstname: "John",
+    Lastname: "Doe",
+}
+```
+
+**RIGHT**
+
+```go
+a := User{
+    Firstname: "John",
+    Lastname:  "Doe",
+}
+```
+
+### Wrapping long function definitions
+
+If the function definition is too long for the 80 character limit, wrap the function definition by writing with as few lines as possible while avoiding trailing open parenthesis and traling commas after the last parameter and the last return type.
+
+**WRONG**
+
+```go
+func doSomething(
+    a,
+    b,
+    c,
+) (d, error) {
+
+func doSomething(a, b, c,
+) (d, error) {
+
+func doSomething(a, b, c) (
+    d, error) {
+```
+
+**RIGHT**
+
+```go
+func doSomething(a, b,
+    c) (d, error) {
+
+func doSomething(a, b, c) (d,
+    error) {
+```
+
+If the function definition spans multiple lines, the function body should start with an empty line to help distinguishing two elements.
--- a/internal/code/extractor_test.go
+++ b/internal/code/extractor_test.go
@ -129,27 +129,50 @@ type UserRepository interface {
 									{Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
 								},
 								Returns: []code.Type{
-									code.ArrayType{ContainedType: code.PointerType{ContainedType: code.SimpleType("UserModel")}},
+									code.ArrayType{
+										ContainedType: code.PointerType{
+											ContainedType: code.SimpleType("UserModel"),
+										},
+									},
 									code.TypeError,
 								},
 							},
 							{
 								Name: "FindByAgeBetween",
 								Params: []code.Param{
-									{Name: "ctx", Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
-									{Name: "fromAge", Type: code.TypeInt},
-									{Name: "toAge", Type: code.TypeInt},
+									{
+										Name: "ctx",
+										Type: code.ExternalType{PackageAlias: "context", Name: "Context"},
+									},
+									{
+										Name: "fromAge",
+										Type: code.TypeInt,
+									},
+									{
+										Name: "toAge",
+										Type: code.TypeInt,
+									},
 								},
 								Returns: []code.Type{
-									code.ArrayType{ContainedType: code.PointerType{ContainedType: code.SimpleType("UserModel")}},
+									code.ArrayType{
+										ContainedType: code.PointerType{
+											ContainedType: code.SimpleType("UserModel"),
+										},
+									},
 									code.TypeError,
 								},
 							},
 							{
 								Name: "InsertOne",
 								Params: []code.Param{
-									{Name: "ctx", Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
-									{Name: "user", Type: code.PointerType{ContainedType: code.SimpleType("UserModel")}},
+									{
+										Name: "ctx",
+										Type: code.ExternalType{PackageAlias: "context", Name: "Context"},
+									},
+									{
+										Name: "user",
+										Type: code.PointerType{ContainedType: code.SimpleType("UserModel")},
+									},
 								},
 								Returns: []code.Type{
 									code.InterfaceType{},
@ -159,9 +182,18 @@ type UserRepository interface {
 							{
 								Name: "UpdateAgreementByID",
 								Params: []code.Param{
-									{Name: "ctx", Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
-									{Name: "agreement", Type: code.MapType{KeyType: code.TypeString, ValueType: code.TypeBool}},
-									{Name: "id", Type: code.ExternalType{PackageAlias: "primitive", Name: "ObjectID"}},
+									{
+										Name: "ctx",
+										Type: code.ExternalType{PackageAlias: "context", Name: "Context"},
+									},
+									{
+										Name: "agreement",
+										Type: code.MapType{KeyType: code.TypeString, ValueType: code.TypeBool},
+									},
+									{
+										Name: "id",
+										Type: code.ExternalType{PackageAlias: "primitive", Name: "ObjectID"},
+									},
 								},
 								Returns: []code.Type{
 									code.TypeBool,
@ -273,7 +305,9 @@ type UserRepository interface {
 									{Name: "ctx", Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
 								},
 								Returns: []code.Type{
-									code.ArrayType{ContainedType: code.PointerType{ContainedType: code.SimpleType("UserModel")}},
+									code.ArrayType{
+										ContainedType: code.PointerType{ContainedType: code.SimpleType("UserModel")},
+									},
 									code.TypeError,
 								},
 							},
--- a/internal/code/package.go
+++ b/internal/code/package.go
@ -24,7 +24,7 @@ func ParsePackage(pkgs map[string]*ast.Package) (Package, error) {
 }

 // Package stores package name, struct and interface implementations as a result
-// from ParsePackage
+// from ParsePackage.
 type Package struct {
 	Name       string
 	Structs    map[string]Struct
--- a/internal/generator/generator_test.go
+++ b/internal/generator/generator_test.go
@ -1,12 +1,13 @@
 package generator_test

 import (
-	"strings"
+	"os"
 	"testing"

 	"github.com/sunboyy/repogen/internal/code"
 	"github.com/sunboyy/repogen/internal/generator"
 	"github.com/sunboyy/repogen/internal/spec"
+	"github.com/sunboyy/repogen/internal/testutils"
 )

 var (
@ -76,8 +77,16 @@ func TestGenerateMongoRepository(t *testing.T) {
 				Query: spec.QuerySpec{
 					Operator: spec.OperatorAnd,
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorNot, ParamIndex: 1},
-						{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorLessThan, ParamIndex: 2},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorNot,
+							ParamIndex:     1,
+						},
+						{
+							FieldReference: spec.FieldReference{ageField},
+							Comparator:     spec.ComparatorLessThan,
+							ParamIndex:     2,
+						},
 					},
 				},
 			},
@ -96,7 +105,11 @@ func TestGenerateMongoRepository(t *testing.T) {
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorLessThanEqual, ParamIndex: 1},
+						{
+							FieldReference: spec.FieldReference{ageField},
+							Comparator:     spec.ComparatorLessThanEqual,
+							ParamIndex:     1,
+						},
 					},
 				},
 				Sorts: []spec.Sort{
@ -118,7 +131,11 @@ func TestGenerateMongoRepository(t *testing.T) {
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThan, ParamIndex: 1},
+						{
+							FieldReference: spec.FieldReference{ageField},
+							Comparator:     spec.ComparatorGreaterThan,
+							ParamIndex:     1,
+						},
 					},
 				},
 				Sorts: []spec.Sort{
@ -140,7 +157,11 @@ func TestGenerateMongoRepository(t *testing.T) {
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThanEqual, ParamIndex: 1},
+						{
+							FieldReference: spec.FieldReference{ageField},
+							Comparator:     spec.ComparatorGreaterThanEqual,
+							ParamIndex:     1,
+						},
 					},
 				},
 				Sorts: []spec.Sort{
@ -163,7 +184,11 @@ func TestGenerateMongoRepository(t *testing.T) {
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorBetween, ParamIndex: 1},
+						{
+							FieldReference: spec.FieldReference{ageField},
+							Comparator:     spec.ComparatorBetween,
+							ParamIndex:     1,
+						},
 					},
 				},
 			},
@ -184,153 +209,33 @@ func TestGenerateMongoRepository(t *testing.T) {
 				Query: spec.QuerySpec{
 					Operator: spec.OperatorOr,
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-						{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     1,
+						},
+						{
+							FieldReference: spec.FieldReference{ageField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     2,
+						},
 					},
 				},
 			},
 		},
 	}
+	expectedBytes, err := os.ReadFile("../../test/generator_test_expected.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	expectedCode := string(expectedBytes)

 	code, err := generator.GenerateRepository("user", userModel, "UserRepository", methods)

 	if err != nil {
+		t.Fatal(err)
+	}
+	if err := testutils.ExpectMultiLineString(expectedCode, code); err != nil {
 		t.Error(err)
 	}
-	expectedCode := `// Code generated by repogen. DO NOT EDIT.
-package user
-
-import (
-	"context"
-
-	"go.mongodb.org/mongo-driver/bson"
-	"go.mongodb.org/mongo-driver/bson/primitive"
-	"go.mongodb.org/mongo-driver/mongo"
-	"go.mongodb.org/mongo-driver/mongo/options"
-)
-
-func NewUserRepository(collection *mongo.Collection) UserRepository {
-	return &UserRepositoryMongo{
-		collection: collection,
-	}
-}
-
-type UserRepositoryMongo struct {
-	collection *mongo.Collection
-}
-
-func (r *UserRepositoryMongo) FindByID(arg0 context.Context, arg1 primitive.ObjectID) (*UserModel, error) {
-	var entity UserModel
-	if err := r.collection.FindOne(arg0, bson.M{
-		"_id": arg1,
-	}, options.FindOne().SetSort(bson.M{})).Decode(&entity); err != nil {
-		return nil, err
-	}
-	return &entity, nil
-}
-
-func (r *UserRepositoryMongo) FindByGenderNotAndAgeLessThan(arg0 context.Context, arg1 Gender, arg2 int) (*UserModel, error) {
-	cursor, err := r.collection.Find(arg0, bson.M{
-		"$and": []bson.M{
-			{"gender": bson.M{"$ne": arg1}},
-			{"age": bson.M{"$lt": arg2}},
-		},
-	}, options.Find().SetSort(bson.M{}))
-	if err != nil {
-		return nil, err
-	}
-	var entities []*UserModel
-	if err := cursor.All(arg0, &entities); err != nil {
-		return nil, err
-	}
-	return entities, nil
-}
-
-func (r *UserRepositoryMongo) FindByAgeLessThanEqualOrderByAge(arg0 context.Context, arg1 int) ([]*UserModel, error) {
-	cursor, err := r.collection.Find(arg0, bson.M{
-		"age": bson.M{"$lte": arg1},
-	}, options.Find().SetSort(bson.M{
-		"age": 1,
-	}))
-	if err != nil {
-		return nil, err
-	}
-	var entities []*UserModel
-	if err := cursor.All(arg0, &entities); err != nil {
-		return nil, err
-	}
-	return entities, nil
-}
-
-func (r *UserRepositoryMongo) FindByAgeGreaterThanOrderByAgeAsc(arg0 context.Context, arg1 int) ([]*UserModel, error) {
-	cursor, err := r.collection.Find(arg0, bson.M{
-		"age": bson.M{"$gt": arg1},
-	}, options.Find().SetSort(bson.M{
-		"age": 1,
-	}))
-	if err != nil {
-		return nil, err
-	}
-	var entities []*UserModel
-	if err := cursor.All(arg0, &entities); err != nil {
-		return nil, err
-	}
-	return entities, nil
-}
-
-func (r *UserRepositoryMongo) FindByAgeGreaterThanEqualOrderByAgeDesc(arg0 context.Context, arg1 int) ([]*UserModel, error) {
-	cursor, err := r.collection.Find(arg0, bson.M{
-		"age": bson.M{"$gte": arg1},
-	}, options.Find().SetSort(bson.M{
-		"age": -1,
-	}))
-	if err != nil {
-		return nil, err
-	}
-	var entities []*UserModel
-	if err := cursor.All(arg0, &entities); err != nil {
-		return nil, err
-	}
-	return entities, nil
-}
-
-func (r *UserRepositoryMongo) FindByAgeBetween(arg0 context.Context, arg1 int, arg2 int) ([]*UserModel, error) {
-	cursor, err := r.collection.Find(arg0, bson.M{
-		"age": bson.M{"$gte": arg1, "$lte": arg2},
-	}, options.Find().SetSort(bson.M{}))
-	if err != nil {
-		return nil, err
-	}
-	var entities []*UserModel
-	if err := cursor.All(arg0, &entities); err != nil {
-		return nil, err
-	}
-	return entities, nil
-}
-
-func (r *UserRepositoryMongo) FindByGenderOrAge(arg0 context.Context, arg1 Gender, arg2 int) ([]*UserModel, error) {
-	cursor, err := r.collection.Find(arg0, bson.M{
-		"$or": []bson.M{
-			{"gender": arg1},
-			{"age": arg2},
-		},
-	}, options.Find().SetSort(bson.M{}))
-	if err != nil {
-		return nil, err
-	}
-	var entities []*UserModel
-	if err := cursor.All(arg0, &entities); err != nil {
-		return nil, err
-	}
-	return entities, nil
-}
-`
-	expectedCodeLines := strings.Split(expectedCode, "\n")
-	actualCodeLines := strings.Split(code, "\n")
-
-	for i, line := range expectedCodeLines {
-		if line != actualCodeLines[i] {
-			t.Errorf("On line %d\nExpected = %v\nActual = %v", i, line, actualCodeLines[i])
-		}
-	}
 }
--- a/internal/mongo/generator.go
+++ b/internal/mongo/generator.go
@ -19,7 +19,8 @@ func NewGenerator(structModel code.Struct, interfaceName string) RepositoryGener
 	}
 }

-// RepositoryGenerator provides repository constructor and method generation from provided specification
+// RepositoryGenerator is a MongoDB repository generator that provides
+// necessary information required to construct an implementation.
 type RepositoryGenerator struct {
 	StructModel   code.Struct
 	InterfaceName string
--- a/internal/mongo/generator_test.go
+++ b/internal/mongo/generator_test.go
@ -1,6 +1,7 @@
 package mongo_test

 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"testing"
@ -318,7 +319,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{idField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{idField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -348,7 +353,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -418,8 +427,16 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Query: spec.QuerySpec{
 						Operator: spec.OperatorAnd,
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 2},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -458,8 +475,16 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Query: spec.QuerySpec{
 						Operator: spec.OperatorOr,
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 2},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -496,7 +521,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorNot, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorNot,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -530,7 +559,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorLessThan, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorLessThan,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -564,7 +597,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorLessThanEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorLessThanEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -598,7 +635,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorGreaterThan, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorGreaterThan,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -632,7 +673,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorGreaterThanEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorGreaterThanEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -667,7 +712,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorBetween, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorBetween,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -701,7 +750,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorIn, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorIn,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -735,7 +788,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorNotIn, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorNotIn,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -768,7 +825,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorTrue, FieldReference: spec.FieldReference{enabledField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorTrue,
+								FieldReference: spec.FieldReference{enabledField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -801,7 +862,11 @@ func TestGenerateMethod_Find(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorFalse, FieldReference: spec.FieldReference{enabledField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorFalse,
+								FieldReference: spec.FieldReference{enabledField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -897,7 +962,10 @@ func TestGenerateMethod_Find(t *testing.T) {
 				Operation: spec.FindOperation{
 					Mode: spec.QueryModeMany,
 					Sorts: []spec.Sort{
-						{FieldReference: spec.FieldReference{nameField, firstNameField}, Ordering: spec.OrderingAscending},
+						{
+							FieldReference: spec.FieldReference{nameField, firstNameField},
+							Ordering:       spec.OrderingAscending,
+						},
 					},
 				},
 			},
@ -1033,7 +1101,11 @@ func TestGenerateMethod_Update(t *testing.T) {
 					Mode:   spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1063,12 +1135,20 @@ func TestGenerateMethod_Update(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{ageField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{ageField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorSet,
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1100,12 +1180,20 @@ func TestGenerateMethod_Update(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{ageField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{ageField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorSet,
+						},
 					},
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{genderField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1137,12 +1225,20 @@ func TestGenerateMethod_Update(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{consentHistoryField}, ParamIndex: 1, Operator: spec.UpdateOperatorPush},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{consentHistoryField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorPush,
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1174,12 +1270,20 @@ func TestGenerateMethod_Update(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{ageField}, ParamIndex: 1, Operator: spec.UpdateOperatorInc},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{ageField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorInc,
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1212,13 +1316,25 @@ func TestGenerateMethod_Update(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{enabledField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
-						spec.UpdateField{FieldReference: spec.FieldReference{consentHistoryField}, ParamIndex: 2, Operator: spec.UpdateOperatorPush},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{enabledField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorSet,
+						},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{consentHistoryField},
+							ParamIndex:     2,
+							Operator:       spec.UpdateOperatorPush,
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 3},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     3,
+							},
 						},
 					},
 				},
@ -1253,12 +1369,20 @@ func TestGenerateMethod_Update(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{nameField, firstNameField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{nameField, firstNameField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorSet,
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1354,7 +1478,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{idField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{idField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1383,7 +1511,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1414,8 +1546,16 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Query: spec.QuerySpec{
 						Operator: spec.OperatorAnd,
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 2},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1449,8 +1589,16 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Query: spec.QuerySpec{
 						Operator: spec.OperatorOr,
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
-							{Comparator: spec.ComparatorEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 2},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
+							{
+								Comparator:     spec.ComparatorEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1482,7 +1630,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorNot, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorNot,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1511,7 +1663,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorLessThan, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorLessThan,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1540,7 +1696,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorLessThanEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorLessThanEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1569,7 +1729,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorGreaterThan, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorGreaterThan,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1598,7 +1762,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorGreaterThanEqual, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorGreaterThanEqual,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1628,7 +1796,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorBetween, FieldReference: spec.FieldReference{ageField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorBetween,
+								FieldReference: spec.FieldReference{ageField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1657,7 +1829,11 @@ func TestGenerateMethod_Delete(t *testing.T) {
 					Mode: spec.QueryModeMany,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{Comparator: spec.ComparatorIn, FieldReference: spec.FieldReference{genderField}, ParamIndex: 1},
+							{
+								Comparator:     spec.ComparatorIn,
+								FieldReference: spec.FieldReference{genderField},
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1751,7 +1927,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{genderField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1781,8 +1961,16 @@ func TestGenerateMethod_Count(t *testing.T) {
 					Query: spec.QuerySpec{
 						Operator: spec.OperatorAnd,
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{genderField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     1,
+							},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1815,8 +2003,16 @@ func TestGenerateMethod_Count(t *testing.T) {
 					Query: spec.QuerySpec{
 						Operator: spec.OperatorOr,
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{genderField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     1,
+							},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -1847,7 +2043,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorNot, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{genderField},
+								Comparator:     spec.ComparatorNot,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1875,7 +2075,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorLessThan, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorLessThan,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1903,7 +2107,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorLessThanEqual, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorLessThanEqual,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1931,7 +2139,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThan, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorGreaterThan,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1959,7 +2171,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThanEqual, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorGreaterThanEqual,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -1988,7 +2204,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorBetween, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorBetween,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -2016,7 +2236,11 @@ func TestGenerateMethod_Count(t *testing.T) {
 				Operation: spec.CountOperation{
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorIn, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{ageField},
+								Comparator:     spec.ComparatorIn,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -2140,7 +2364,11 @@ func TestGenerateMethod_Invalid(t *testing.T) {
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{accessTokenField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+							{
+								FieldReference: spec.FieldReference{accessTokenField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     1,
+							},
 						},
 					},
 				},
@ -2182,12 +2410,20 @@ func TestGenerateMethod_Invalid(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{accessTokenField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{accessTokenField},
+							ParamIndex:     1,
+							Operator:       spec.UpdateOperatorSet,
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -2212,7 +2448,11 @@ func TestGenerateMethod_Invalid(t *testing.T) {
 					Mode:   spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -2234,12 +2474,20 @@ func TestGenerateMethod_Invalid(t *testing.T) {
 				},
 				Operation: spec.UpdateOperation{
 					Update: spec.UpdateFields{
-						spec.UpdateField{FieldReference: spec.FieldReference{consentHistoryField}, ParamIndex: 1, Operator: "APPEND"},
+						spec.UpdateField{
+							FieldReference: spec.FieldReference{consentHistoryField},
+							ParamIndex:     1,
+							Operator:       "APPEND",
+						},
 					},
 					Mode: spec.QueryModeOne,
 					Query: spec.QuerySpec{
 						Predicates: []spec.Predicate{
-							{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+							{
+								FieldReference: spec.FieldReference{idField},
+								Comparator:     spec.ComparatorEqual,
+								ParamIndex:     2,
+							},
 						},
 					},
 				},
@ -2254,7 +2502,7 @@ func TestGenerateMethod_Invalid(t *testing.T) {

 			_, err := generator.GenerateMethod(testCase.Method)

-			if err != testCase.ExpectedError {
+			if !errors.Is(err, testCase.ExpectedError) {
 				t.Errorf("\nExpected = %+v\nReceived = %+v", testCase.ExpectedError, err)
 			}
 		})
--- a/internal/spec/errors.go
+++ b/internal/spec/errors.go
@ -1,35 +1,19 @@
 package spec

 import (
+	"errors"
 	"fmt"
 	"strings"

 	"github.com/sunboyy/repogen/internal/code"
 )

-// ParsingError is an error from parsing interface methods
-type ParsingError string
-
-func (err ParsingError) Error() string {
-	switch err {
-	case QueryRequiredError:
-		return "query is required"
-	case InvalidParamError:
-		return "parameters do not match the query"
-	case InvalidUpdateFieldsError:
-		return "update fields are invalid"
-	case ContextParamRequiredError:
-		return "context parameter is required"
-	}
-	return string(err)
-}
-
 // parsing error constants
-const (
-	QueryRequiredError        ParsingError = "ERROR_QUERY_REQUIRED"
-	InvalidParamError         ParsingError = "ERROR_INVALID_PARAM"
-	InvalidUpdateFieldsError  ParsingError = "ERROR_INVALID_UPDATE_FIELDS"
-	ContextParamRequiredError ParsingError = "ERROR_CONTEXT_PARAM_REQUIRED"
+var (
+	ErrQueryRequired        = errors.New("spec: query is required")
+	ErrInvalidParam         = errors.New("spec: parameters do not match the query")
+	ErrInvalidUpdateFields  = errors.New("spec: update fields are invalid")
+	ErrContextParamRequired = errors.New("spec: context parameter is required")
 )

 // NewUnsupportedReturnError creates unsupportedReturnError
@ -49,7 +33,8 @@ func (err unsupportedReturnError) Error() string {
 	return fmt.Sprintf("return type '%s' at index %d is not supported", err.GivenType.Code(), err.Index)
 }

-// NewOperationReturnCountUnmatchedError creates operationReturnCountUnmatchedError
+// NewOperationReturnCountUnmatchedError creates
+// operationReturnCountUnmatchedError.
 func NewOperationReturnCountUnmatchedError(returnCount int) error {
 	return operationReturnCountUnmatchedError{
 		ReturnCount: returnCount,
--- a/internal/spec/field.go
+++ b/internal/spec/field.go
@ -14,7 +14,8 @@ func (r FieldReference) ReferencedField() code.StructField {
 	return r[len(r)-1]
 }

-// ReferencingCode returns a string containing name of the referenced fields concatenating with period (.).
+// ReferencingCode returns a string containing name of the referenced fields
+// concatenating with period (.).
 func (r FieldReference) ReferencingCode() string {
 	var fieldNames []string
 	for _, field := range r {
--- a/internal/spec/parser.go
+++ b/internal/spec/parser.go
@ -5,8 +5,11 @@ import (
 	"github.com/sunboyy/repogen/internal/code"
 )

-// ParseInterfaceMethod returns repository method spec from declared interface method
-func ParseInterfaceMethod(structs map[string]code.Struct, structModel code.Struct, method code.Method) (MethodSpec, error) {
+// ParseInterfaceMethod returns repository method spec from declared interface
+// method.
+func ParseInterfaceMethod(structs map[string]code.Struct, structModel code.Struct,
+	method code.Method) (MethodSpec, error) {
+
 	parser := interfaceMethodParser{
 		fieldResolver: fieldResolver{
 			Structs: structs,
@ -67,12 +70,12 @@ func (p interfaceMethodParser) parseInsertOperation(tokens []string) (Operation,

 	pointerType := code.PointerType{ContainedType: p.StructModel.ReferencedType()}
 	if mode == QueryModeOne && p.Method.Params[1].Type != pointerType {
-		return nil, InvalidParamError
+		return nil, ErrInvalidParam
 	}

 	arrayType := code.ArrayType{ContainedType: pointerType}
 	if mode == QueryModeMany && p.Method.Params[1].Type != arrayType {
-		return nil, InvalidParamError
+		return nil, ErrInvalidParam
 	}

 	return InsertOperation{
@ -354,14 +357,14 @@ func (p interfaceMethodParser) extractIntOrBoolReturns(returns []code.Type) (Que
 func (p interfaceMethodParser) validateContextParam() error {
 	contextType := code.ExternalType{PackageAlias: "context", Name: "Context"}
 	if len(p.Method.Params) == 0 || p.Method.Params[0].Type != contextType {
-		return ContextParamRequiredError
+		return ErrContextParamRequired
 	}
 	return nil
 }

 func (p interfaceMethodParser) validateQueryFromParams(params []code.Param, querySpec QuerySpec) error {
 	if querySpec.NumberOfArguments() != len(params) {
-		return InvalidParamError
+		return ErrInvalidParam
 	}

 	var currentParamIndex int
@ -373,7 +376,9 @@ func (p interfaceMethodParser) validateQueryFromParams(params []code.Param, quer
 		}

 		for i := 0; i < predicate.Comparator.NumberOfArguments(); i++ {
-			requiredType := predicate.Comparator.ArgumentTypeFromFieldType(predicate.FieldReference.ReferencedField().Type)
+			requiredType := predicate.Comparator.ArgumentTypeFromFieldType(
+				predicate.FieldReference.ReferencedField().Type,
+			)

 			if params[currentParamIndex].Type != requiredType {
 				return NewArgumentTypeNotMatchedError(predicate.FieldReference.ReferencingCode(), requiredType,
--- a/internal/spec/parser_test.go
+++ b/internal/spec/parser_test.go
@ -1,6 +1,7 @@
 package spec_test

 import (
+	"errors"
 	"reflect"
 	"testing"

@ -126,8 +127,19 @@ func TestParseInterfaceMethod_Insert(t *testing.T) {
 			Method: code.Method{
 				Name: "InsertMany",
 				Params: []code.Param{
-					{Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
-					{Type: code.ArrayType{ContainedType: code.PointerType{ContainedType: code.SimpleType("UserModel")}}},
+					{
+						Type: code.ExternalType{
+							PackageAlias: "context",
+							Name:         "Context",
+						},
+					},
+					{
+						Type: code.ArrayType{
+							ContainedType: code.PointerType{
+								ContainedType: code.SimpleType("UserModel"),
+							},
+						},
+					},
 				},
 				Returns: []code.Type{
 					code.ArrayType{ContainedType: code.InterfaceType{}},
@ -198,7 +210,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeOne,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{phoneNumberField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{phoneNumberField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -238,7 +254,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{nameField, firstNameField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{nameField, firstNameField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -258,7 +278,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{referrerField, idField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{referrerField, idField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -297,8 +321,16 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 				Query: spec.QuerySpec{
 					Operator: spec.OperatorAnd,
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{cityField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+						{
+							FieldReference: spec.FieldReference{cityField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     1,
+						},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     2,
+						},
 					},
 				},
 			},
@ -322,8 +354,16 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 				Query: spec.QuerySpec{
 					Operator: spec.OperatorOr,
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{cityField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+						{
+							FieldReference: spec.FieldReference{cityField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     1,
+						},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     2,
+						},
 					},
 				},
 			},
@ -384,7 +424,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorLessThanEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{ageField},
+						Comparator:     spec.ComparatorLessThanEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -404,7 +448,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThan, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{ageField},
+						Comparator:     spec.ComparatorGreaterThan,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -424,7 +472,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThanEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{ageField},
+						Comparator:     spec.ComparatorGreaterThanEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -523,7 +575,11 @@ func TestParseInterfaceMethod_Find(t *testing.T) {
 			ExpectedOperation: spec.FindOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{enabledField}, Comparator: spec.ComparatorFalse, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{enabledField},
+						Comparator:     spec.ComparatorFalse,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -705,11 +761,19 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{genderField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{genderField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorSet,
+					},
 				},
 				Mode: spec.QueryModeOne,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+					{
+						FieldReference: spec.FieldReference{idField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     2,
+					},
 				}},
 			},
 		},
@ -729,11 +793,19 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{genderField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{genderField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorSet,
+					},
 				},
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+					{
+						FieldReference: spec.FieldReference{idField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     2,
+					},
 				}},
 			},
 		},
@ -753,11 +825,19 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{nameField, firstNameField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{nameField, firstNameField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorSet,
+					},
 				},
 				Mode: spec.QueryModeOne,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+					{
+						FieldReference: spec.FieldReference{idField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     2,
+					},
 				}},
 			},
 		},
@ -778,8 +858,16 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{genderField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
-					spec.UpdateField{FieldReference: spec.FieldReference{cityField}, ParamIndex: 2, Operator: spec.UpdateOperatorSet},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{genderField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorSet,
+					},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{cityField},
+						ParamIndex:     2,
+						Operator:       spec.UpdateOperatorSet,
+					},
 				},
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
@ -803,11 +891,19 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{consentHistoryField}, ParamIndex: 1, Operator: spec.UpdateOperatorPush},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{consentHistoryField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorPush,
+					},
 				},
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+					{
+						FieldReference: spec.FieldReference{idField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     2,
+					},
 				}},
 			},
 		},
@ -827,11 +923,19 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{ageField}, ParamIndex: 1, Operator: spec.UpdateOperatorInc},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{ageField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorInc,
+					},
 				},
 				Mode: spec.QueryModeOne,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{idField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+					{
+						FieldReference: spec.FieldReference{idField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     2,
+					},
 				}},
 			},
 		},
@ -852,8 +956,16 @@ func TestParseInterfaceMethod_Update(t *testing.T) {
 			},
 			ExpectedOperation: spec.UpdateOperation{
 				Update: spec.UpdateFields{
-					spec.UpdateField{FieldReference: spec.FieldReference{enabledField}, ParamIndex: 1, Operator: spec.UpdateOperatorSet},
-					spec.UpdateField{FieldReference: spec.FieldReference{consentHistoryField}, ParamIndex: 2, Operator: spec.UpdateOperatorPush},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{enabledField},
+						ParamIndex:     1,
+						Operator:       spec.UpdateOperatorSet,
+					},
+					spec.UpdateField{
+						FieldReference: spec.FieldReference{consentHistoryField},
+						ParamIndex:     2,
+						Operator:       spec.UpdateOperatorPush,
+					},
 				},
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
@ -921,7 +1033,11 @@ func TestParseInterfaceMethod_Delete(t *testing.T) {
 			ExpectedOperation: spec.DeleteOperation{
 				Mode: spec.QueryModeOne,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{phoneNumberField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{phoneNumberField},
+						Comparator:     spec.ComparatorEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -980,8 +1096,16 @@ func TestParseInterfaceMethod_Delete(t *testing.T) {
 				Query: spec.QuerySpec{
 					Operator: spec.OperatorAnd,
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{cityField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+						{
+							FieldReference: spec.FieldReference{cityField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     1,
+						},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     2,
+						},
 					},
 				},
 			},
@ -1005,8 +1129,16 @@ func TestParseInterfaceMethod_Delete(t *testing.T) {
 				Query: spec.QuerySpec{
 					Operator: spec.OperatorOr,
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{cityField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 2},
+						{
+							FieldReference: spec.FieldReference{cityField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     1,
+						},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     2,
+						},
 					},
 				},
 			},
@ -1067,7 +1199,11 @@ func TestParseInterfaceMethod_Delete(t *testing.T) {
 			ExpectedOperation: spec.DeleteOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorLessThanEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{ageField},
+						Comparator:     spec.ComparatorLessThanEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -1087,7 +1223,11 @@ func TestParseInterfaceMethod_Delete(t *testing.T) {
 			ExpectedOperation: spec.DeleteOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThan, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{ageField},
+						Comparator:     spec.ComparatorGreaterThan,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -1107,7 +1247,11 @@ func TestParseInterfaceMethod_Delete(t *testing.T) {
 			ExpectedOperation: spec.DeleteOperation{
 				Mode: spec.QueryModeMany,
 				Query: spec.QuerySpec{Predicates: []spec.Predicate{
-					{FieldReference: spec.FieldReference{ageField}, Comparator: spec.ComparatorGreaterThanEqual, ParamIndex: 1},
+					{
+						FieldReference: spec.FieldReference{ageField},
+						Comparator:     spec.ComparatorGreaterThanEqual,
+						ParamIndex:     1,
+					},
 				}},
 			},
 		},
@ -1208,7 +1352,11 @@ func TestParseInterfaceMethod_Count(t *testing.T) {
 			ExpectedOperation: spec.CountOperation{
 				Query: spec.QuerySpec{
 					Predicates: []spec.Predicate{
-						{FieldReference: spec.FieldReference{genderField}, Comparator: spec.ComparatorEqual, ParamIndex: 1},
+						{
+							FieldReference: spec.FieldReference{genderField},
+							Comparator:     spec.ComparatorEqual,
+							ParamIndex:     1,
+						},
 					},
 				},
 			},
@ -1247,7 +1395,7 @@ func TestParseInterfaceMethod_Invalid(t *testing.T) {
 	})

 	expectedError := spec.NewUnknownOperationError("Search")
-	if err != expectedError {
+	if !errors.Is(err, expectedError) {
 		t.Errorf("\nExpected = %+v\nReceived = %+v", expectedError, err)
 	}
 }
@ -1275,7 +1423,10 @@ func TestParseInterfaceMethod_Insert_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.NewUnsupportedReturnError(code.PointerType{ContainedType: code.SimpleType("UserModel")}, 0),
+			ExpectedError: spec.NewUnsupportedReturnError(
+				code.PointerType{ContainedType: code.SimpleType("UserModel")},
+				0,
+			),
 		},
 		{
 			Name: "unempty interface return from insert method",
@ -1315,22 +1466,32 @@ func TestParseInterfaceMethod_Insert_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.ContextParamRequiredError,
+			ExpectedError: spec.ErrContextParamRequired,
 		},
 		{
 			Name: "mismatched model parameter for one mode",
 			Method: code.Method{
 				Name: "Insert",
 				Params: []code.Param{
-					{Name: "ctx", Type: code.ExternalType{PackageAlias: "context", Name: "Context"}},
-					{Name: "userModel", Type: code.ArrayType{ContainedType: code.PointerType{ContainedType: code.SimpleType("UserModel")}}},
+					{
+						Name: "ctx",
+						Type: code.ExternalType{PackageAlias: "context", Name: "Context"},
+					},
+					{
+						Name: "userModel",
+						Type: code.ArrayType{
+							ContainedType: code.PointerType{
+								ContainedType: code.SimpleType("UserModel"),
+							},
+						},
+					},
 				},
 				Returns: []code.Type{
 					code.InterfaceType{},
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidParamError,
+			ExpectedError: spec.ErrInvalidParam,
 		},
 		{
 			Name: "mismatched model parameter for many mode",
@ -1345,7 +1506,7 @@ func TestParseInterfaceMethod_Insert_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidParamError,
+			ExpectedError: spec.ErrInvalidParam,
 		},
 	}

@ -1405,7 +1566,7 @@ func TestParseInterfaceMethod_Find_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.QueryRequiredError,
+			ExpectedError: spec.ErrQueryRequired,
 		},
 		{
 			Name: "misplaced operator token (leftmost)",
@ -1463,7 +1624,7 @@ func TestParseInterfaceMethod_Find_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.ContextParamRequiredError,
+			ExpectedError: spec.ErrContextParamRequired,
 		},
 		{
 			Name: "mismatched number of parameters",
@ -1479,7 +1640,7 @@ func TestParseInterfaceMethod_Find_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidParamError,
+			ExpectedError: spec.ErrInvalidParam,
 		},
 		{
 			Name: "struct field not found",
@ -1711,7 +1872,7 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidUpdateFieldsError,
+			ExpectedError: spec.ErrInvalidUpdateFields,
 		},
 		{
 			Name: "misplaced And token in update fields",
@ -1725,7 +1886,7 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidUpdateFieldsError,
+			ExpectedError: spec.ErrInvalidUpdateFields,
 		},
 		{
 			Name: "push operator in non-array field",
@ -1782,7 +1943,7 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.QueryRequiredError,
+			ExpectedError: spec.ErrQueryRequired,
 		},
 		{
 			Name: "ambiguous query",
@ -1813,8 +1974,13 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.NewArgumentTypeNotMatchedError(consentHistoryField.Name, code.SimpleType("ConsentHistoryItem"),
-				code.ArrayType{ContainedType: code.SimpleType("ConsentHistoryItem")}),
+			ExpectedError: spec.NewArgumentTypeNotMatchedError(
+				consentHistoryField.Name,
+				code.SimpleType("ConsentHistoryItem"),
+				code.ArrayType{
+					ContainedType: code.SimpleType("ConsentHistoryItem"),
+				},
+			),
 		},
 		{
 			Name: "insufficient function parameters",
@ -1829,7 +1995,7 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidUpdateFieldsError,
+			ExpectedError: spec.ErrInvalidUpdateFields,
 		},
 		{
 			Name: "update model with invalid parameter",
@ -1844,7 +2010,7 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidUpdateFieldsError,
+			ExpectedError: spec.ErrInvalidUpdateFields,
 		},
 		{
 			Name: "no context parameter",
@ -1859,7 +2025,7 @@ func TestParseInterfaceMethod_Update_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.ContextParamRequiredError,
+			ExpectedError: spec.ErrContextParamRequired,
 		},
 		{
 			Name: "struct field not found in update fields",
@ -1967,7 +2133,7 @@ func TestParseInterfaceMethod_Delete_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.QueryRequiredError,
+			ExpectedError: spec.ErrQueryRequired,
 		},
 		{
 			Name: "misplaced operator token (leftmost)",
@ -2025,7 +2191,7 @@ func TestParseInterfaceMethod_Delete_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.ContextParamRequiredError,
+			ExpectedError: spec.ErrContextParamRequired,
 		},
 		{
 			Name: "mismatched number of parameters",
@ -2041,7 +2207,7 @@ func TestParseInterfaceMethod_Delete_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidParamError,
+			ExpectedError: spec.ErrInvalidParam,
 		},
 		{
 			Name: "struct field not found",
@ -2147,7 +2313,7 @@ func TestParseInterfaceMethod_Count_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.QueryRequiredError,
+			ExpectedError: spec.ErrQueryRequired,
 		},
 		{
 			Name: "invalid query",
@ -2172,7 +2338,7 @@ func TestParseInterfaceMethod_Count_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.ContextParamRequiredError,
+			ExpectedError: spec.ErrContextParamRequired,
 		},
 		{
 			Name: "mismatched number of parameter",
@ -2188,7 +2354,7 @@ func TestParseInterfaceMethod_Count_Invalid(t *testing.T) {
 					code.TypeError,
 				},
 			},
-			ExpectedError: spec.InvalidParamError,
+			ExpectedError: spec.ErrInvalidParam,
 		},
 		{
 			Name: "mismatched method parameter type",
--- a/internal/spec/query.go
+++ b/internal/spec/query.go
@ -46,7 +46,8 @@ const (
 	ComparatorFalse            Comparator = "EQUAL_FALSE"
 )

-// ArgumentTypeFromFieldType returns a type of required argument from the given struct field type
+// ArgumentTypeFromFieldType returns a type of required argument from the given
+// struct field type.
 func (c Comparator) ArgumentTypeFromFieldType(t code.Type) code.Type {
 	switch c {
 	case ComparatorIn, ComparatorNotIn:
@ -56,7 +57,8 @@ func (c Comparator) ArgumentTypeFromFieldType(t code.Type) code.Type {
 	}
 }

-// NumberOfArguments returns the number of arguments required to perform the comparison
+// NumberOfArguments returns the number of arguments required to perform the
+// comparison.
 func (c Comparator) NumberOfArguments() int {
 	switch c {
 	case ComparatorBetween:
@ -82,7 +84,7 @@ type queryParser struct {

 func (p queryParser) parseQuery(rawTokens []string, paramIndex int) (QuerySpec, error) {
 	if len(rawTokens) == 0 {
-		return QuerySpec{}, QueryRequiredError
+		return QuerySpec{}, ErrQueryRequired
 	}

 	tokens := rawTokens
--- a/internal/spec/update.go
+++ b/internal/spec/update.go
@ -47,14 +47,16 @@ func (u UpdateFields) NumberOfArguments() int {
 	return len(u)
 }

-// UpdateField stores mapping between field name in the model and the parameter index
+// UpdateField stores mapping between field name in the model and the parameter
+// index.
 type UpdateField struct {
 	FieldReference FieldReference
 	ParamIndex     int
 	Operator       UpdateOperator
 }

-// UpdateOperator is a custom type that declares update operator to be used in an update operation
+// UpdateOperator is a custom type that declares update operator to be used in
+// an update operation
 type UpdateOperator string

 // UpdateOperator constants
@ -117,14 +119,14 @@ func (p interfaceMethodParser) parseUpdate(tokens []string) (Update, error) {
 	if len(tokens) == 0 {
 		requiredType := code.PointerType{ContainedType: p.StructModel.ReferencedType()}
 		if len(p.Method.Params) <= 1 || p.Method.Params[1].Type != requiredType {
-			return nil, InvalidUpdateFieldsError
+			return nil, ErrInvalidUpdateFields
 		}
 		return UpdateModel{}, nil
 	}

 	updateFieldTokens, ok := splitByAnd(tokens)
 	if !ok {
-		return nil, InvalidUpdateFieldsError
+		return nil, ErrInvalidUpdateFields
 	}

 	var updateFields UpdateFields
@ -142,7 +144,7 @@ func (p interfaceMethodParser) parseUpdate(tokens []string) (Update, error) {

 	for _, field := range updateFields {
 		if len(p.Method.Params) < field.ParamIndex+field.Operator.NumberOfArguments() {
-			return nil, InvalidUpdateFieldsError
+			return nil, ErrInvalidUpdateFields
 		}

 		requiredType := field.Operator.ArgumentType(field.FieldReference.ReferencedField().Type)
@ -158,7 +160,9 @@ func (p interfaceMethodParser) parseUpdate(tokens []string) (Update, error) {
 	return updateFields, nil
 }

-func (p interfaceMethodParser) parseUpdateField(t []string, paramIndex int) (UpdateField, error) {
+func (p interfaceMethodParser) parseUpdateField(t []string,
+	paramIndex int) (UpdateField, error) {
+
 	if len(t) > 1 && t[len(t)-1] == "Push" {
 		return p.createUpdateField(t[:len(t)-1], UpdateOperatorPush, paramIndex)
 	}
@ -168,7 +172,9 @@ func (p interfaceMethodParser) parseUpdateField(t []string, paramIndex int) (Upd
 	return p.createUpdateField(t, UpdateOperatorSet, paramIndex)
 }

-func (p interfaceMethodParser) createUpdateField(t []string, operator UpdateOperator, paramIndex int) (UpdateField, error) {
+func (p interfaceMethodParser) createUpdateField(t []string,
+	operator UpdateOperator, paramIndex int) (UpdateField, error) {
+
 	fieldReference, ok := p.fieldResolver.ResolveStructField(p.StructModel, t)
 	if !ok {
 		return UpdateField{}, NewStructFieldNotFoundError(t)
--- a/internal/testutils/multilines.go
+++ b/internal/testutils/multilines.go
@ -5,7 +5,8 @@ import (
 	"strings"
 )

-// ExpectMultiLineString compares two multi-line strings and report the difference
+// ExpectMultiLineString compares two multi-line strings and report the
+// difference.
 func ExpectMultiLineString(expected, actual string) error {
 	expectedLines := strings.Split(expected, "\n")
 	actualLines := strings.Split(actual, "\n")
@ -17,14 +18,14 @@ func ExpectMultiLineString(expected, actual string) error {

 	for i := 0; i < numberOfComparableLines; i++ {
 		if expectedLines[i] != actualLines[i] {
-			return fmt.Errorf("On line %d\nExpected: %v\nReceived: %v", i+1, expectedLines[i], actualLines[i])
+			return fmt.Errorf("at line %d\nexpected: %v\nreceived: %v", i+1, expectedLines[i], actualLines[i])
 		}
 	}

 	if len(expectedLines) < len(actualLines) {
-		return fmt.Errorf("Unexpected lines:\n%s", strings.Join(actualLines[len(expectedLines):], "\n"))
+		return fmt.Errorf("unexpected lines:\n%s", strings.Join(actualLines[len(expectedLines):], "\n"))
 	} else if len(expectedLines) > len(actualLines) {
-		return fmt.Errorf("Missing lines:\n%s", strings.Join(expectedLines[len(actualLines):], "\n"))
+		return fmt.Errorf("missing lines:\n%s", strings.Join(expectedLines[len(actualLines):], "\n"))
 	}

 	return nil
--- a/internal/testutils/multilines_test.go
+++ b/internal/testutils/multilines_test.go
@ -28,9 +28,9 @@ How are you?`

 		err := testutils.ExpectMultiLineString(expectedText, actualText)

-		expectedError := "On line 2\nExpected: this is an expected text\nReceived: this is a real text"
+		expectedError := "at line 2\nexpected: this is an expected text\nreceived: this is a real text"
 		if err == nil || err.Error() != expectedError {
-			t.Errorf("Expected = %s\nReceived = %s", expectedError, err.Error())
+			t.Errorf("expected = %s\nreceived = %s", expectedError, err.Error())
 		}
 	})

@ -46,9 +46,9 @@ how are you?`

 		err := testutils.ExpectMultiLineString(expectedText, actualText)

-		expectedError := "Missing lines:\nI'm fine...\nThank you..."
+		expectedError := "missing lines:\nI'm fine...\nThank you..."
 		if err == nil || err.Error() != expectedError {
-			t.Errorf("Expected = %s\nReceived = %s", expectedError, err.Error())
+			t.Errorf("expected = %s\nreceived = %s", expectedError, err.Error())
 		}
 	})

@ -64,9 +64,9 @@ Thank you...`

 		err := testutils.ExpectMultiLineString(expectedText, actualText)

-		expectedError := "Unexpected lines:\nI'm fine...\nThank you..."
+		expectedError := "unexpected lines:\nI'm fine...\nThank you..."
 		if err == nil || err.Error() != expectedError {
-			t.Errorf("Expected = %s\nReceived = %s", expectedError, err.Error())
+			t.Errorf("expected = %s\nreceived = %s", expectedError, err.Error())
 		}
 	})
 }
--- a/test/generator_test_expected.txt
+++ b/test/generator_test_expected.txt
@ -0,0 +1,127 @@
+// Code generated by repogen. DO NOT EDIT.
+package user
+
+import (
+	"context"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+)
+
+func NewUserRepository(collection *mongo.Collection) UserRepository {
+	return &UserRepositoryMongo{
+		collection: collection,
+	}
+}
+
+type UserRepositoryMongo struct {
+	collection *mongo.Collection
+}
+
+func (r *UserRepositoryMongo) FindByID(arg0 context.Context, arg1 primitive.ObjectID) (*UserModel, error) {
+	var entity UserModel
+	if err := r.collection.FindOne(arg0, bson.M{
+		"_id": arg1,
+	}, options.FindOne().SetSort(bson.M{})).Decode(&entity); err != nil {
+		return nil, err
+	}
+	return &entity, nil
+}
+
+func (r *UserRepositoryMongo) FindByGenderNotAndAgeLessThan(arg0 context.Context, arg1 Gender, arg2 int) (*UserModel, error) {
+	cursor, err := r.collection.Find(arg0, bson.M{
+		"$and": []bson.M{
+			{"gender": bson.M{"$ne": arg1}},
+			{"age": bson.M{"$lt": arg2}},
+		},
+	}, options.Find().SetSort(bson.M{}))
+	if err != nil {
+		return nil, err
+	}
+	var entities []*UserModel
+	if err := cursor.All(arg0, &entities); err != nil {
+		return nil, err
+	}
+	return entities, nil
+}
+
+func (r *UserRepositoryMongo) FindByAgeLessThanEqualOrderByAge(arg0 context.Context, arg1 int) ([]*UserModel, error) {
+	cursor, err := r.collection.Find(arg0, bson.M{
+		"age": bson.M{"$lte": arg1},
+	}, options.Find().SetSort(bson.M{
+		"age": 1,
+	}))
+	if err != nil {
+		return nil, err
+	}
+	var entities []*UserModel
+	if err := cursor.All(arg0, &entities); err != nil {
+		return nil, err
+	}
+	return entities, nil
+}
+
+func (r *UserRepositoryMongo) FindByAgeGreaterThanOrderByAgeAsc(arg0 context.Context, arg1 int) ([]*UserModel, error) {
+	cursor, err := r.collection.Find(arg0, bson.M{
+		"age": bson.M{"$gt": arg1},
+	}, options.Find().SetSort(bson.M{
+		"age": 1,
+	}))
+	if err != nil {
+		return nil, err
+	}
+	var entities []*UserModel
+	if err := cursor.All(arg0, &entities); err != nil {
+		return nil, err
+	}
+	return entities, nil
+}
+
+func (r *UserRepositoryMongo) FindByAgeGreaterThanEqualOrderByAgeDesc(arg0 context.Context, arg1 int) ([]*UserModel, error) {
+	cursor, err := r.collection.Find(arg0, bson.M{
+		"age": bson.M{"$gte": arg1},
+	}, options.Find().SetSort(bson.M{
+		"age": -1,
+	}))
+	if err != nil {
+		return nil, err
+	}
+	var entities []*UserModel
+	if err := cursor.All(arg0, &entities); err != nil {
+		return nil, err
+	}
+	return entities, nil
+}
+
+func (r *UserRepositoryMongo) FindByAgeBetween(arg0 context.Context, arg1 int, arg2 int) ([]*UserModel, error) {
+	cursor, err := r.collection.Find(arg0, bson.M{
+		"age": bson.M{"$gte": arg1, "$lte": arg2},
+	}, options.Find().SetSort(bson.M{}))
+	if err != nil {
+		return nil, err
+	}
+	var entities []*UserModel
+	if err := cursor.All(arg0, &entities); err != nil {
+		return nil, err
+	}
+	return entities, nil
+}
+
+func (r *UserRepositoryMongo) FindByGenderOrAge(arg0 context.Context, arg1 Gender, arg2 int) ([]*UserModel, error) {
+	cursor, err := r.collection.Find(arg0, bson.M{
+		"$or": []bson.M{
+			{"gender": arg1},
+			{"age": arg2},
+		},
+	}, options.Find().SetSort(bson.M{}))
+	if err != nil {
+		return nil, err
+	}
+	var entities []*UserModel
+	if err := cursor.All(arg0, &entities); err != nil {
+		return nil, err
+	}
+	return entities, nil
+}