test(render): improve test coverage

json_test.go

@@ -2,6 +2,8 @@ package render_test
 
 import (
 	"bytes"
+	"encoding/json"
+	"errors"
 	"testing"
 
 	"github.com/jimeh/go-render"
@@ -9,6 +11,17 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type mockJSONMarshaler struct {
+	data []byte
+	err  error
+}
+
+var _ json.Marshaler = (*mockJSONMarshaler)(nil)
+
+func (mjm *mockJSONMarshaler) MarshalJSON() ([]byte, error) {
+	return mjm.data, mjm.err
+}
+
 func TestJSON_Render(t *testing.T) {
 	tests := []struct {
 		name      string
@@ -29,18 +42,35 @@ func TestJSON_Render(t *testing.T) {
 		{
 			name:   "simple object with pretty",
 			pretty: true,
-			indent: "  ",
 			value:  map[string]int{"age": 30},
 			want:   "{\n  \"age\": 30\n}\n",
 		},
 		{
-			name:   "with prefix and indent",
+			name:   "pretty with prefix and indent",
 			pretty: true,
 			prefix: "// ",
 			indent: "\t",
 			value:  map[string]int{"age": 30},
 			want:   "{\n// \t\"age\": 30\n// }\n",
 		},
+		{
+			name:   "prefix and indent without pretty",
+			pretty: false,
+			prefix: "// ",
+			indent: "\t",
+			value:  map[string]int{"age": 30},
+			want:   "{\"age\":30}\n",
+		},
+		{
+			name:  "implements json.Marshaler",
+			value: &mockJSONMarshaler{data: []byte(`{"age":30}`)},
+			want:  "{\"age\":30}\n",
+		},
+		{
+			name:      "error from json.Marshaler",
+			value:     &mockJSONMarshaler{err: errors.New("marshal error!!1")},
+			wantErrIs: []error{render.Err},
+		},
 		{
 			name:      "invalid value",
 			pretty:    false,
@@ -49,7 +79,6 @@ func TestJSON_Render(t *testing.T) {
 			wantErrIs: []error{render.Err},
 		},
 	}
-
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			j := &render.JSON{
@@ -57,9 +86,10 @@ func TestJSON_Render(t *testing.T) {
 				Prefix: tt.prefix,
 				Indent: tt.indent,
 			}
-
 			var buf bytes.Buffer
+
 			err := j.Render(&buf, tt.value)
+			got := buf.String()
 
 			if tt.wantErr != "" {
 				require.Error(t, err)
@@ -71,7 +101,6 @@ func TestJSON_Render(t *testing.T) {
 
 			if tt.wantErr == "" && len(tt.wantErrIs) == 0 {
 				require.NoError(t, err)
-				got := buf.String()
 				assert.Equal(t, tt.want, got)
 			}
 		})