Add output tests

Author: telegrapher

output/output_test.go

@@ -0,0 +1,82 @@
+// Copyright 2025 Adobe. All rights reserved.
+// This file is licensed to you under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License. You may obtain a copy
+// of the License at http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software distributed under
+// the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
+// OF ANY KIND, either express or implied. See the License for the specific language
+// governing permissions and limitations under the License.
+
+package output
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// captureStdout captures the output of a function that writes to stdout.
+func captureStdout(t *testing.T, fn func()) string {
+	t.Helper()
+	old := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to create pipe: %v", err)
+	}
+	os.Stdout = w
+
+	fn()
+
+	w.Close()
+	os.Stdout = old
+
+	var buf bytes.Buffer
+	if _, err := io.Copy(&buf, r); err != nil {
+		t.Fatalf("failed to read pipe: %v", err)
+	}
+	return buf.String()
+}
+
+// loadExpected reads the expected output from a golden file in testdata/.
+func loadExpected(t *testing.T, filename string) string {
+	t.Helper()
+	data, err := os.ReadFile(filepath.Join("testdata", filename))
+	if err != nil {
+		t.Fatalf("failed to read golden file %s: %v", filename, err)
+	}
+	return string(data)
+}
+
+func TestPrintPrettyJSON(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		file  string
+	}{
+		{name: "compact object is prettified", input: `{"name":"John","age":30}`, file: "compact_object.json"},
+		{name: "already indented JSON is normalized", input: "{\n    \"key\": \"value\"\n}", file: "already_indented.json"},
+		{name: "compact array is prettified", input: `[{"id":1},{"id":2}]`, file: "compact_array.json"},
+		{name: "empty object", input: `{}`, file: "empty_object.json"},
+		{name: "empty array", input: `[]`, file: "empty_array.json"},
+		{name: "nested objects", input: `{"a":{"b":{"c":1}}}`, file: "nested_objects.json"},
+		{name: "non-JSON is printed as-is", input: "this is not JSON", file: "non_json.txt"},
+		{name: "empty string is printed as-is", input: "", file: "empty_string.txt"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			expected := loadExpected(t, tt.file)
+
+			got := captureStdout(t, func() {
+				PrintPrettyJSON(tt.input)
+			})
+
+			if got != expected {
+				t.Errorf("PrintPrettyJSON(%q)\ngot:\n%s\nexpected output is in testdata/%s", tt.input, got, tt.file)
+			}
+		})
+	}
+}

output/testdata/empty_string.txt

@@ -0,0 +1 @@
+

output/testdata/non_json.txt

@@ -0,0 +1 @@
+this is not JSON