Fix validation errors builder string

.gitignore

@@ -1,2 +1,5 @@
 vendor
 gomock_generator/gomock_generator
+
+# IDE
+.idea/

errors/validation_errors.go

@@ -1,7 +1,7 @@
 package errors
 
 import (
-	"bytes"
+	"fmt"
 	"strings"
 )
 
@@ -11,14 +11,18 @@ type ValidationErrors struct {
 }
 
 func (v *ValidationErrors) Error() string {
-	var buffer bytes.Buffer
+	var builder strings.Builder
+	index := 0
 
-	for field, errors := range v.Errors {
-		buffer.WriteString(field)
-		buffer.WriteString("=")
-		buffer.WriteString(strings.Join(errors, ","))
+	for field, errs := range v.Errors {
+		index++
+		builder.WriteString(fmt.Sprintf("%s=%s", field, strings.Join(errs, ", ")))
+		if index < len(v.Errors) {
+			builder.WriteString(" ")
+		}
 	}
-	return buffer.String()
+
+	return builder.String()
 }
 
 // ValidationErrorsBuilder is used to provide a simple way to create a ValidationErrors struct. The typical usecase is:

errors/validation_errors_test.go

@@ -1,7 +1,10 @@
 package errors
 
-import "github.com/stretchr/testify/require"
-import "testing"
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
 
 func TestValidationErrorsBuilder_Merge(t *testing.T) {
 	cases := map[string]struct {
@@ -60,3 +63,42 @@ func TestValidationErrorsBuilder_MergeWithPrefix(t *testing.T) {
 		})
 	}
 }
+
+func TestValidationErrors_Error(t *testing.T) {
+	cases := map[string]struct {
+		Errors         ValidationErrors
+		ExpectedString string
+	}{
+		"should return a string with one error in it": {
+			Errors: ValidationErrors{
+				Errors: map[string][]string{
+					"name": {"invalid name"},
+				},
+			},
+			ExpectedString: "name=invalid name",
+		},
+		"should return a string with multiple errors in it with the same field name": {
+			Errors: ValidationErrors{
+				Errors: map[string][]string{
+					"name": {"invalid name", "should contains alphanumeric characters"},
+				},
+			},
+			ExpectedString: "name=invalid name, should contains alphanumeric characters",
+		},
+		"should return a string with multiple errors in it with multiple field name": {
+			Errors: ValidationErrors{
+				Errors: map[string][]string{
+					"name": {"invalid name", "should contains alphanumeric characters"},
+					"type": {"invalid type", "type not exist"},
+				},
+			},
+			ExpectedString: "name=invalid name, should contains alphanumeric characters type=invalid type, type not exist",
+		},
+	}
+
+	for title, c := range cases {
+		t.Run(title, func(t *testing.T) {
+			require.Equal(t, c.ExpectedString, c.Errors.Error())
+		})
+	}
+}