Core: Add QUnit.config.testFilter

Add programmatic callback to filter tests at runtime. Useful for
quarantining flaky tests, parallel test sharding, and runtime
capability detection.

The callback receives testInfo { testId, testName, module, skip }
and returns true to run the test or false to skip it.

Author: gbudjeakp

demos/testFilter.js

@@ -0,0 +1,293 @@
+/**
+ * Demo: QUnit.config.testFilter
+ *
+ * The testFilter callback allows you to programmatically filter which tests run
+ * at runtime. This is useful for CI workflows, flaky test quarantine, dynamic
+ * test selection, and other advanced scenarios.
+ */
+
+// ============================================================================
+// Example: Combined testFilter implementation
+// ============================================================================
+
+// Quarantine list - in production, load from JSON file or API
+const quarantineList = ['flaky network test', 'timing-dependent test'];
+
+QUnit.config.testFilter = function (testInfo) {
+  // testInfo contains: { testId, testName, module, skip }
+
+  // 1. Skip quarantined tests in CI
+  if (process.env.CI === 'true') {
+    const isQuarantined = quarantineList.some(function (pattern) {
+      return testInfo.testName.indexOf(pattern) !== -1;
+    });
+    if (isQuarantined) {
+      console.log('[QUARANTINE] Skipping: ' + testInfo.module + ' > ' + testInfo.testName);
+      return false;
+    }
+  }
+
+  // 2. Skip slow tests in quick mode
+  if (process.env.QUICK_RUN === 'true') {
+    if (testInfo.testName.toLowerCase().indexOf('slow') !== -1) {
+      console.log('[QUICK_RUN] Skipping slow test: ' + testInfo.testName);
+      return false;
+    }
+  }
+
+  // 3. Filter by module name if specified
+  if (process.env.TEST_MODULE) {
+    if (testInfo.module.indexOf(process.env.TEST_MODULE) === -1) {
+      return false;
+    }
+  }
+
+  // 4. Parallel sharding - distribute tests across workers
+  if (process.env.WORKER_ID !== undefined) {
+    const WORKER_ID = parseInt(process.env.WORKER_ID, 10);
+    const TOTAL_WORKERS = parseInt(process.env.TOTAL_WORKERS || '1', 10);
+
+    let hash = 0;
+    for (let i = 0; i < testInfo.testId.length; i++) {
+      const char = testInfo.testId.charCodeAt(i);
+      hash = ((hash << 5) - hash) + char;
+      hash = hash & hash;
+    }
+    hash = Math.abs(hash);
+
+    const assignedWorker = hash % TOTAL_WORKERS;
+    if (assignedWorker !== WORKER_ID) {
+      return false;
+    }
+    console.log('  [Worker ' + WORKER_ID + '] Running: ' + testInfo.module + ' > ' + testInfo.testName);
+  }
+
+  // 5. Feature detection - skip tests for unavailable features
+  // Tests tagged with [feature] in name are checked against runtime capabilities
+  const features = {
+    webgl: typeof WebGLRenderingContext !== 'undefined',
+    webrtc: typeof RTCPeerConnection !== 'undefined',
+    serviceWorker: typeof navigator !== 'undefined' && 'serviceWorker' in navigator,
+    indexedDB: typeof indexedDB !== 'undefined'
+  };
+
+  for (const feature in features) {
+    const tag = '[' + feature + ']';
+    if (testInfo.testName.indexOf(tag) !== -1 && !features[feature]) {
+      console.log('[FEATURE] Skipping ' + feature + ' test: ' + testInfo.testName);
+      return false;
+    }
+  }
+
+  return true;
+};
+
+// ============================================================================
+// Example 2: Quarantine flaky tests in CI
+// ============================================================================
+
+if (process.env.CI === 'true') {
+  // In production, this list might come from a JSON file or API
+  const quarantineList = [
+    'flaky network test',
+    'timing-dependent test',
+    'unreliable integration test'
+  ];
+
+  QUnit.config.testFilter = function (testInfo) {
+    const isQuarantined = quarantineList.some(pattern =>
+      testInfo.testName.includes(pattern)
+    );
+
+    if (isQuarantined) {
+      console.log(`[QUARANTINE] Skipping: ${testInfo.module} > ${testInfo.testName}`);
+      return false;
+    }
+
+    return true;
+  };
+}
+
+// ============================================================================
+// Example 3: Filter by module name
+// ============================================================================
+
+// Run only tests from specific modules
+if (process.env.TEST_MODULE) {
+  const targetModule = process.env.TEST_MODULE;
+
+  QUnit.config.testFilter = function (testInfo) {
+    const moduleMatches = testInfo.module.includes(targetModule);
+
+    if (!moduleMatches) {
+      console.log(`[MODULE_FILTER] Skipping: ${testInfo.module}`);
+    }
+
+    return moduleMatches;
+  };
+}
+
+// ============================================================================
+// Example 4: Feature flags - Run tests based on runtime capabilities
+// ============================================================================
+
+// Check if certain features are available at runtime
+const features = {
+  webgl: typeof WebGLRenderingContext !== 'undefined',
+  webrtc: typeof RTCPeerConnection !== 'undefined',
+  serviceWorker: typeof navigator !== 'undefined' && 'serviceWorker' in navigator,
+  indexedDB: typeof indexedDB !== 'undefined'
+};
+
+QUnit.config.testFilter = function (testInfo) {
+  for (const [feature, available] of Object.entries(features)) {
+    if (testInfo.testName.includes(`[${feature}]`) && !available) {
+      console.log(`[FEATURE_FLAG] Skipping ${feature} test: ${testInfo.testName}`);
+      return false;
+    }
+  }
+
+  return true;
+};
+
+// ============================================================================
+// Example 5: Parallel test sharding across workers
+// ============================================================================
+
+if (process.env.WORKER_ID !== undefined) {
+  const WORKER_ID = parseInt(process.env.WORKER_ID, 10);
+  const TOTAL_WORKERS = parseInt(process.env.TOTAL_WORKERS || '1', 10);
+
+  console.log(`Worker ${WORKER_ID + 1} of ${TOTAL_WORKERS}`);
+
+  function hashTestId (testId) {
+    let hash = 0;
+    for (let i = 0; i < testId.length; i++) {
+      const char = testId.charCodeAt(i);
+      hash = ((hash << 5) - hash) + char;
+      hash = hash & hash;
+    }
+    return Math.abs(hash);
+  }
+
+  QUnit.config.testFilter = function (testInfo) {
+    const hash = hashTestId(testInfo.testId);
+    const assignedWorker = hash % TOTAL_WORKERS;
+    const shouldRun = assignedWorker === WORKER_ID;
+
+    if (shouldRun) {
+      console.log(`  [Worker ${WORKER_ID}] Running: ${testInfo.module} > ${testInfo.testName}`);
+    }
+
+    return shouldRun;
+  };
+}
+
+// ============================================================================
+// Example 6: Combine multiple filter conditions
+// ============================================================================
+
+QUnit.config.testFilter = function (testInfo) {
+  // Skip quarantined tests
+  const quarantined = ['flaky test'];
+  if (quarantined.some(pattern => testInfo.testName.includes(pattern))) {
+    return false;
+  }
+
+  // Skip slow tests in quick mode
+  if (process.env.QUICK_RUN && testInfo.testName.includes('slow')) {
+    return false;
+  }
+
+  // Only run tests from specific module if specified
+  if (process.env.TEST_MODULE && !testInfo.module.includes(process.env.TEST_MODULE)) {
+    return false;
+  }
+
+  return true;
+};
+
+// ============================================================================
+// Example tests
+// ============================================================================
+
+QUnit.module('Fast tests', function () {
+  QUnit.test('quick calculation', function (assert) {
+    assert.equal(2 + 2, 4);
+  });
+
+  QUnit.test('string operation', function (assert) {
+    assert.equal('test'.toUpperCase(), 'TEST');
+  });
+});
+
+QUnit.module('Slow tests', function () {
+  QUnit.test('slow database query', function (assert) {
+    assert.ok(true);
+  });
+
+  QUnit.test('slow network request', function (assert) {
+    assert.ok(true);
+  });
+});
+
+QUnit.module('Integration tests', function () {
+  QUnit.test('API integration', function (assert) {
+    assert.ok(true);
+  });
+
+  QUnit.test('flaky network test', function (assert) {
+    assert.ok(true);
+  });
+
+  QUnit.test('timing-dependent test', function (assert) {
+    assert.ok(true);
+  });
+});
+
+QUnit.module('Feature-specific tests', function () {
+  QUnit.test('[webgl] 3D rendering', function (assert) {
+    assert.ok(true, 'WebGL test');
+  });
+
+  QUnit.test('[webrtc] peer connection', function (assert) {
+    assert.ok(true, 'WebRTC test');
+  });
+
+  QUnit.test('[serviceWorker] caching', function (assert) {
+    assert.ok(true, 'Service Worker test');
+  });
+
+  QUnit.test('[indexedDB] storage', function (assert) {
+    assert.ok(true, 'IndexedDB test');
+  });
+});
+
+// ============================================================================
+// Usage Examples:
+// ============================================================================
+//
+// Skip slow tests:
+//   QUICK_RUN=true node bin/qunit.js demos/testFilter.js
+//
+// Run only "Fast tests" module:
+//   TEST_MODULE="Fast tests" node bin/qunit.js demos/testFilter.js
+//
+// Enable quarantine in CI:
+//   CI=true node bin/qunit.js demos/testFilter.js
+//
+// Parallel execution with 3 workers:
+//   WORKER_ID=0 TOTAL_WORKERS=3 node bin/qunit.js demos/testFilter.js
+//   WORKER_ID=1 TOTAL_WORKERS=3 node bin/qunit.js demos/testFilter.js
+//   WORKER_ID=2 TOTAL_WORKERS=3 node bin/qunit.js demos/testFilter.js
+//
+// ============================================================================
+// Notes:
+// ============================================================================
+//
+// - testFilter runs AFTER test.only/test.skip/test.if checks
+// - testFilter runs BEFORE CLI --filter and --module parameters
+// - Return true to run the test, false to skip it
+// - Thrown errors are logged but don't stop the test run
+// - testInfo.skip is true if test was already marked to skip
+//