fix(output): use UTC timestamps and improve test patterns

- Use UTC time methods for consistent timestamped filenames
- Make regex patterns more specific to match exact timestamp format
- Replace 1100ms delay test with Date mocking for faster execution

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: boneskull

src/core/output-path-resolver.ts

@@ -4,12 +4,13 @@ import { extname, isAbsolute, join, resolve } from 'node:path';
  * Generates a timestamped filename for benchmark output files.
  *
  * @param extension - File extension without the dot (e.g., 'json', 'csv')
- * @returns Filename in format `benchmarks-YYYY-MM-DD-HH-MM-SS.{extension}`
+ * @returns Filename in format `benchmarks-YYYY-MM-DD-HH-MM-SS.{extension}` (UTC
+ *   time)
  */
 export const generateTimestampedFilename = (extension: string): string => {
   const now = new Date();
   const pad = (n: number) => n.toString().padStart(2, '0');
-  const timestamp = `${now.getFullYear()}-${pad(now.getMonth() + 1)}-${pad(now.getDate())}-${pad(now.getHours())}-${pad(now.getMinutes())}-${pad(now.getSeconds())}`;
+  const timestamp = `${now.getUTCFullYear()}-${pad(now.getUTCMonth() + 1)}-${pad(now.getUTCDate())}-${pad(now.getUTCHours())}-${pad(now.getUTCMinutes())}-${pad(now.getUTCSeconds())}`;
   return `benchmarks-${timestamp}.${extension}`;
 };
 

test/integration/quiet-mode.test.ts

@@ -158,15 +158,15 @@ describe('Quiet Mode Integration Tests', () => {
       // Both JSON and CSV files should be written with timestamped names
       const jsonFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.json$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.json$/,
       );
       expect(jsonFile, 'to be truthy');
       const jsonContent = await readFile(jsonFile!, 'utf-8');
       expect(jsonContent, 'to match', /"meta":/);
 
       const csvFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.csv$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.csv$/,
       );
       expect(csvFile, 'to be truthy');
       const csvContent = await readFile(csvFile!, 'utf-8');
@@ -227,7 +227,7 @@ describe('Quiet Mode Integration Tests', () => {
       // Verify file was written with timestamped name
       const outputFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.json$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.json$/,
       );
       expect(outputFile, 'to be truthy');
       const fileExists = existsSync(outputFile!);

test/integration/reporters.test.ts

@@ -245,11 +245,11 @@ describe('Multiple reporter output formats', () => {
       // Should create json and csv files with timestamped names
       const jsonFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.json$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.json$/,
       );
       const csvFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.csv$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.csv$/,
       );
 
       expect(jsonFile, 'to be truthy');
@@ -305,7 +305,7 @@ describe('Multiple reporter output formats', () => {
       // Should create nested directories and timestamped files
       const jsonFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.json$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.json$/,
       );
       expect(jsonFile, 'to be truthy');
       const jsonContent = await readFile(jsonFile!, 'utf-8');

test/integration/verbose-mode.test.ts

@@ -251,7 +251,7 @@ describe('Verbose Mode Integration Tests', () => {
       // JSON data should be written to file with timestamped name
       const jsonFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.json$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.json$/,
       );
       expect(jsonFile, 'to be truthy');
       const jsonContent = await readFile(jsonFile!, 'utf-8');
@@ -277,7 +277,7 @@ describe('Verbose Mode Integration Tests', () => {
       // JSON data should be written to file with timestamped name
       const jsonFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.json$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.json$/,
       );
       expect(jsonFile, 'to be truthy');
       const jsonContent = await readFile(jsonFile!, 'utf-8');
@@ -307,7 +307,7 @@ describe('Verbose Mode Integration Tests', () => {
       // CSV data should be written to file with timestamped name
       const csvFile = await findFileByPattern(
         outputDir,
-        /^benchmarks-.*\.csv$/,
+        /^benchmarks-\d{4}-\d{2}-\d{2}-\d{2}-\d{2}-\d{2}\.csv$/,
       );
       expect(csvFile, 'to be truthy');
       const csvContent = await readFile(csvFile!, 'utf-8');

test/unit/output-path-resolver.test.ts

@@ -76,12 +76,42 @@ describe('generateTimestampedFilename', () => {
     );
   });
 
-  it('should generate different filenames at different times', async () => {
-    const result1 = generateTimestampedFilename('json');
-    // Wait a second to ensure different timestamp
-    await new Promise((resolve) => setTimeout(resolve, 1100));
-    const result2 = generateTimestampedFilename('json');
-    expect(result1, 'not to equal', result2);
+  it('should generate different filenames at different times', () => {
+    const RealDate = globalThis.Date;
+
+    const fixedTime1 = new RealDate('2020-01-01T00:00:00Z').getTime();
+    const fixedTime2 = new RealDate('2020-01-01T00:00:01Z').getTime();
+
+    const mockDate = (ms: number) => {
+      const MockDate = class extends RealDate {
+        constructor(...args: Parameters<typeof RealDate>) {
+          if (args.length === 0) {
+            super(ms);
+          } else {
+            super(...args);
+          }
+        }
+
+        static override now() {
+          return ms;
+        }
+      };
+      globalThis.Date = MockDate as typeof Date;
+    };
+
+    try {
+      mockDate(fixedTime1);
+      const result1 = generateTimestampedFilename('json');
+
+      mockDate(fixedTime2);
+      const result2 = generateTimestampedFilename('json');
+
+      expect(result1, 'not to equal', result2);
+      expect(result1, 'to equal', 'benchmarks-2020-01-01-00-00-00.json');
+      expect(result2, 'to equal', 'benchmarks-2020-01-01-00-00-01.json');
+    } finally {
+      globalThis.Date = RealDate;
+    }
   });
 
   it('should use zero-padded date and time components', () => {