test: add tests for codec/json package to improve coverage

codec/json/json_test.go

@@ -0,0 +1,53 @@
+// Copyright 2025 Gin Core Team. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestJSONMarshal(t *testing.T) {
+	data := map[string]string{"key": "value"}
+	result, err := API.Marshal(data)
+	require.NoError(t, err)
+	assert.JSONEq(t, `{"key":"value"}`, string(result))
+}
+
+func TestJSONUnmarshal(t *testing.T) {
+	var data map[string]string
+	err := API.Unmarshal([]byte(`{"key":"value"}`), &data)
+	require.NoError(t, err)
+	assert.Equal(t, "value", data["key"])
+}
+
+func TestJSONMarshalIndent(t *testing.T) {
+	data := map[string]string{"key": "value"}
+	result, err := API.MarshalIndent(data, "", "  ")
+	require.NoError(t, err)
+	assert.Contains(t, string(result), `"key": "value"`)
+}
+
+func TestJSONNewEncoder(t *testing.T) {
+	var buf bytes.Buffer
+	encoder := API.NewEncoder(&buf)
+	require.NotNil(t, encoder)
+	err := encoder.Encode(map[string]string{"key": "value"})
+	require.NoError(t, err)
+	assert.JSONEq(t, `{"key":"value"}`, buf.String())
+}
+
+func TestJSONNewDecoder(t *testing.T) {
+	buf := bytes.NewBufferString(`{"key":"value"}`)
+	decoder := API.NewDecoder(buf)
+	require.NotNil(t, decoder)
+	var data map[string]string
+	err := decoder.Decode(&data)
+	require.NoError(t, err)
+	assert.Equal(t, "value", data["key"])
+}