Move unmarshalJSON unit tests

Move the Test_unmarshalJSON tests and supporting TestUnmarshaler type 
into a dedicated decode_internal_test.go file and remove the duplicate 
test code from yaml_test.go.

This isolates JSON-unmarshaling-specific tests for unmarshalJSON into a
focused test file, improving test organization and making the intent of
these tests clearer. The tests cover maps with string, int, and any keys,
including a duplicate-key error case, and assert correct conversion to the
TestUnmarshaler struct.

Author: SVilgelm

decode_internal_test.go

@@ -0,0 +1,95 @@
+package yaml
+
+import (
+	"encoding/json"
+	"testing"
+
+	"go.yaml.in/yaml/v4/internal/testutil/assert"
+)
+
+type TestUnmarshaler struct {
+	Value string
+	Array []int
+	Map   map[string]int
+}
+
+func (t *TestUnmarshaler) UnmarshalJSON(data []byte) error {
+	type Alias TestUnmarshaler
+	var aux Alias
+	if err := json.Unmarshal(data, &aux); err != nil {
+		return err
+	}
+	*t = TestUnmarshaler(aux)
+	return nil
+}
+
+func Test_unmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    any
+		expected any
+		wantErr  string
+	}{
+		{
+			name: "map with string keys",
+			input: map[string]any{
+				"Value": "hello",
+				"Array": []int{1, 2, 3},
+				"Map":   map[string]int{"a": 1, "b": 2},
+			},
+			expected: &TestUnmarshaler{
+				Value: "hello",
+				Array: []int{1, 2, 3},
+				Map:   map[string]int{"a": 1, "b": 2},
+			},
+		},
+		{
+			name: "map with int keys",
+			input: map[string]any{
+				"Value": "hello",
+				"Array": []int{1, 2, 3},
+				"Map":   map[int]int{1: 1, 2: 2},
+			},
+			expected: &TestUnmarshaler{
+				Value: "hello",
+				Array: []int{1, 2, 3},
+				Map:   map[string]int{"1": 1, "2": 2},
+			},
+		},
+		{
+			name: "map with any keys",
+			input: map[string]any{
+				"Value": "hello",
+				"Array": []int{1, 2, 3},
+				"Map":   map[any]int{1: 1, "b": 2, true: 3},
+			},
+			expected: &TestUnmarshaler{
+				Value: "hello",
+				Array: []int{1, 2, 3},
+				Map:   map[string]int{"1": 1, "b": 2, "true": 3},
+			},
+		},
+		{
+			name: "map with duplicate keys",
+			input: map[string]any{
+				"Value": "hello",
+				"Array": []int{1, 2, 3},
+				"Map":   map[any]int{1: 1, "1": 2},
+			},
+			wantErr: `duplicate key "1" found when converting to JSON object`,
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			target := &TestUnmarshaler{}
+			err := unmarshalJSON(tt.input, target)
+			if tt.wantErr != "" {
+				assert.ErrorMatchesf(t, tt.wantErr, err, "unmarshalJSON() error")
+				return
+			}
+			assert.NoError(t, err)
+			assert.DeepEqualf(t, tt.expected, target, "unmarshalJSON() result")
+		})
+	}
+}

yaml_test.go

@@ -455,90 +455,3 @@ func ExampleEncoder_FallbackToJSON() {
 	//
 	// true
 }
-
-type TestUnmarshaler struct {
-	Value string
-	Array []int
-	Map   map[string]int
-}
-
-func (t *TestUnmarshaler) UnmarshalJSON(data []byte) error {
-	type Alias TestUnmarshaler
-	var aux Alias
-	if err := json.Unmarshal(data, &aux); err != nil {
-		return err
-	}
-	*t = TestUnmarshaler(aux)
-	return nil
-}
-
-func Test_unmarshalJSON(t *testing.T) {
-	tests := []struct {
-		name     string
-		input    any
-		expected any
-		wantErr  string
-	}{
-		{
-			name: "map with string keys",
-			input: map[string]any{
-				"Value": "hello",
-				"Array": []int{1, 2, 3},
-				"Map":   map[string]int{"a": 1, "b": 2},
-			},
-			expected: &TestUnmarshaler{
-				Value: "hello",
-				Array: []int{1, 2, 3},
-				Map:   map[string]int{"a": 1, "b": 2},
-			},
-		},
-		{
-			name: "map with int keys",
-			input: map[string]any{
-				"Value": "hello",
-				"Array": []int{1, 2, 3},
-				"Map":   map[int]int{1: 1, 2: 2},
-			},
-			expected: &TestUnmarshaler{
-				Value: "hello",
-				Array: []int{1, 2, 3},
-				Map:   map[string]int{"1": 1, "2": 2},
-			},
-		},
-		{
-			name: "map with any keys",
-			input: map[string]any{
-				"Value": "hello",
-				"Array": []int{1, 2, 3},
-				"Map":   map[any]int{1: 1, "b": 2, true: 3},
-			},
-			expected: &TestUnmarshaler{
-				Value: "hello",
-				Array: []int{1, 2, 3},
-				Map:   map[string]int{"1": 1, "b": 2, "true": 3},
-			},
-		},
-		{
-			name: "map with duplicate keys",
-			input: map[string]any{
-				"Value": "hello",
-				"Array": []int{1, 2, 3},
-				"Map":   map[any]int{1: 1, "1": 2},
-			},
-			wantErr: `duplicate key "1" found when converting to JSON object`,
-		},
-	}
-	for _, tt := range tests {
-		tt := tt
-		t.Run(tt.name, func(t *testing.T) {
-			target := &TestUnmarshaler{}
-			err := unmarshalJSON(tt.input, target)
-			if tt.wantErr != "" {
-				assert.ErrorMatchesf(t, tt.wantErr, err, "unmarshalJSON() error")
-				return
-			}
-			assert.NoError(t, err)
-			assert.DeepEqualf(t, tt.expected, target, "unmarshalJSON() result")
-		})
-	}
-}