feat: determine if test is slow (#91)

Author: lokshunhung

integrationTests/__fixtures__/slow/__src__/file1.js

@@ -0,0 +1,2 @@
+// ⚔️🏃
+console.log();

integrationTests/__fixtures__/slow/jest.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  runner: require.resolve('../../runner'),
+  testMatch: ['**/__src__/**/*.js'],
+  slowTestThreshold: -1, // Set this to negative so all tests are slow
+};

integrationTests/__snapshots__/slow.test.js.snap

@@ -0,0 +1,12 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Works when it has slow tests 1`] = `
+"PASS integrationTests/__fixtures__/slow/__src__/file1.js ()
+  ✓
+Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:
+Ran all test suites.
+"
+`;

integrationTests/slow.test.js

@@ -0,0 +1,4 @@
+const runJest = require('./runJest');
+
+it('Works when it has slow tests', () =>
+  expect(runJest('slow')).resolves.toMatchSnapshot());

lib/createJestRunner.ts

@@ -1,9 +1,21 @@
 import type { Config } from '@jest/types';
+import type { TestResult } from '@jest/test-result';
 import type * as JestRunner from 'jest-runner';
 import { Worker } from 'jest-worker';
 import throat from 'throat';
 import type { CreateRunnerOptions, Path, TestRunner } from './types';
 
+function determineSlowTestResult(
+  test: JestRunner.Test,
+  result: TestResult,
+): TestResult {
+  // See: https://github.com/facebook/jest/blob/acd7c83c8365140f4ecf44a456ff7366ffa31fa2/packages/jest-runner/src/runTest.ts#L287
+  if (result.perfStats.runtime / 1000 > test.context.config.slowTestThreshold) {
+    return { ...result, perfStats: { ...result.perfStats, slow: true } };
+  }
+  return result;
+}
+
 class CancelRun extends Error {
   constructor(message?: string) {
     super(message);
@@ -89,6 +101,7 @@ export default function createRunner<
                   return runner(baseOptions);
                 });
               })
+              .then(result => determineSlowTestResult(test, result))
               .then(result => onResult(test, result))
               .catch(err => onFailure(test, err)),
           ),
@@ -146,6 +159,7 @@ export default function createRunner<
       const runAllTests = Promise.all(
         tests.map(test =>
           runTestInWorker(test)
+            .then(result => determineSlowTestResult(test, result))
             .then(testResult => onResult(test, testResult))
             .catch(error => onFailure(test, error)),
         ),

lib/toTestResult.ts

@@ -25,8 +25,7 @@ function getPerfStats({ stats }: Options): TestResult['perfStats'] {
   const start = new Date(stats.start).getTime();
   const end = new Date(stats.end).getTime();
   const runtime = end - start;
-  // TODO: determine `slow` by using `runtime / 1000 > config.slowTestThreshold`
-  // See: https://github.com/facebook/jest/blob/acd7c83c8365140f4ecf44a456ff7366ffa31fa2/packages/jest-runner/src/runTest.ts#L287
+  // Note: this flag is set in 'lib/createJestRunner.ts'
   const slow = false;
   return { start, end, runtime, slow };
 }