Parallelize E2E tests to cut CI time in half (#16417)

* Experiment with parallellizing E2E

* Fix lint

* Try parallelism 8

* Apply suggestions from code review

Co-authored-by: Mark Stacey <markjstacey@gmail.com>

Co-authored-by: Mark Stacey <markjstacey@gmail.com>

.circleci/config.yml

@@ -516,6 +516,7 @@ jobs:
 
   test-e2e-chrome:
     executor: node-browsers
+    parallelism: 8
     steps:
       - checkout
       - run:
@@ -543,6 +544,7 @@ jobs:
     
   test-e2e-chrome-mv3:
     executor: node-browsers
+    parallelism: 8
     steps:
       - checkout
       - run:
@@ -570,6 +572,7 @@ jobs:
 
   test-e2e-firefox-snaps:
     executor: node-browsers
+    parallelism: 2
     steps:
       - checkout
       - run:
@@ -597,6 +600,7 @@ jobs:
 
   test-e2e-chrome-snaps:
     executor: node-browsers
+    parallelism: 2
     steps:
       - checkout
       - run:
@@ -624,6 +628,7 @@ jobs:
 
   test-e2e-firefox:
     executor: node-browsers-medium-plus
+    parallelism: 8
     steps:
       - checkout
       - run:

test/e2e/run-all.js

@@ -13,6 +13,14 @@ const getTestPathsForTestDir = async (testDir) => {
   return testPaths;
 };
 
+function chunk(array, chunkSize) {
+  const result = [];
+  for (let i = 0; i < array.length; i += chunkSize) {
+    result.push(array.slice(i, i + chunkSize));
+  }
+  return result;
+}
+
 async function main() {
   const { argv } = yargs(hideBin(process.argv))
     .usage(
@@ -66,7 +74,14 @@ async function main() {
     args.push('--retries', retries);
   }
 
-  for (const testPath of testPaths) {
+  // For running E2Es in parallel in CI
+  const currentChunkIndex = process.env.CIRCLE_NODE_INDEX ?? 0;
+  const totalChunks = process.env.CIRCLE_NODE_TOTAL ?? 1;
+  const chunkSize = Math.ceil(testPaths.length / totalChunks);
+  const chunks = chunk(testPaths, chunkSize);
+  const currentChunk = chunks[currentChunkIndex];
+
+  for (const testPath of currentChunk) {
     await runInShell('node', [...args, testPath]);
   }
 }