Parallelize Jest in CI (#19552)

Uses CircleCI's `parallelism` key to split our test jobs across multiple
processes, like we do for the build job.

.circleci/config.yml

@@ -19,6 +19,8 @@ aliases:
       name: Install Packages
       command: yarn --frozen-lockfile
 
+  - &TEST_PARALLELISM 20
+
   - &attach_workspace
     at: build
 
@@ -92,6 +94,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
 
     steps:
       - checkout
@@ -102,6 +105,7 @@ jobs:
   yarn_test:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -111,6 +115,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_www:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -120,6 +125,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_www_variant:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -129,6 +135,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_prod_www:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -138,6 +145,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_prod_www_variant:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -147,6 +155,7 @@ jobs:
   yarn_test_www:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -156,6 +165,7 @@ jobs:
   yarn_test_www_variant:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -165,6 +175,7 @@ jobs:
   yarn_test_prod_www:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -174,6 +185,7 @@ jobs:
   yarn_test_prod_www_variant:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -183,6 +195,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_persistent:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
 
     steps:
       - checkout
@@ -193,6 +206,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_prod:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
 
     steps:
       - checkout
@@ -203,6 +217,7 @@ jobs:
   yarn_test_prod:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -212,7 +227,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_build:
     docker: *docker
     environment: *environment
-    parallelism: 20
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - *restore_yarn_cache
@@ -344,6 +359,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_build:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - attach_workspace: *attach_workspace
@@ -354,6 +370,7 @@ jobs:
   yarn_test_build:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - attach_workspace: *attach_workspace
@@ -404,6 +421,7 @@ jobs:
   RELEASE_CHANNEL_stable_yarn_test_build_prod:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - attach_workspace: *attach_workspace
@@ -414,6 +432,7 @@ jobs:
   yarn_test_build_prod:
     docker: *docker
     environment: *environment
+    parallelism: *TEST_PARALLELISM
     steps:
       - checkout
       - attach_workspace: *attach_workspace

packages/react/src/__tests__/ReactClassEquivalence-test.js

@@ -38,6 +38,10 @@ function runJest(testFile) {
     cwd,
     env: Object.assign({}, process.env, {
       REACT_CLASS_EQUIVALENCE_TEST: 'true',
+      // Remove these so that the test file is not filtered out by the mechanism
+      // we use to parallelize tests in CI
+      CIRCLE_NODE_TOTAL: '',
+      CIRCLE_NODE_INDEX: '',
     }),
   });
 

scripts/jest/config.base.js

@@ -22,6 +22,8 @@ module.exports = {
   timers: 'fake',
   snapshotSerializers: [require.resolve('jest-snapshot-serializer-raw')],
 
+  testSequencer: require.resolve('./jestSequencer'),
+
   // TODO: Upgrade to Jest 26 which uses jsdom 16 by default.
   testEnvironment: require.resolve('jest-environment-jsdom-sixteen'),
 };

scripts/jest/jestSequencer.js

@@ -0,0 +1,19 @@
+'use strict';
+
+const Sequencer = require('@jest/test-sequencer').default;
+
+class CustomSequencer extends Sequencer {
+  sort(tests) {
+    if (process.env.CIRCLE_NODE_TOTAL) {
+      // In CI, parallelize tests across multiple tasks.
+      const nodeTotal = parseInt(process.env.CIRCLE_NODE_TOTAL, 10);
+      const nodeIndex = parseInt(process.env.CIRCLE_NODE_INDEX, 10);
+      tests = tests
+        .sort((a, b) => (a.path < b.path ? -1 : 1))
+        .filter((_, i) => i % nodeTotal === nodeIndex);
+    }
+    return tests;
+  }
+}
+
+module.exports = CustomSequencer;