chore: improve jest speed on both local and CI

jest.preset.js

@@ -9,6 +9,8 @@ const tsPathAliases = pathsToModuleNameMapper(tsConfig.compilerOptions.paths, {
   prefix: `<rootDir>/${path.relative(process.cwd(), __dirname)}/`,
 });
 
+const isCI = Boolean(process.env.TF_BUILD);
+
 /**
  * @type {import('@jest/types').Config.InitialOptions}
  */
@@ -29,6 +31,17 @@ const baseConfig = {
     escapeString: true,
     printBasicPrototype: true,
   },
+  /**
+   *  **Local Machine:**
+   *
+   * jest is resource greedy. on local machine it will spawn workers into all your CPU threads which will provide additional heat up of your machine and everything else will be blocked.
+   * Based on tests on local machine, 50% of CPU threads is the best value for local development ( also the fastest).
+   *
+   *  **CI:**
+   *
+   * not spawning additional workers provides FASTER jest runs on CI.
+   */
+  maxWorkers: isCI ? 1 : '50%',
 };
 
 module.exports = {

scripts/jest/src/jest.preset.v0.js

@@ -1,6 +1,5 @@
 const { getWorkspaceProjectsAliases } = require('@fluentui/scripts-monorepo');
 
-const { isCI } = require('./environment');
 const { workersConfig } = require('./shared');
 
 // northstar packages should pull these from npm, not the repo
@@ -21,7 +20,7 @@ const createConfig = (/** @type {import('@jest/types').Config.InitialOptions} */
   testEnvironment: 'jsdom',
   restoreMocks: true,
   clearMocks: true,
-  ...(isCI ? workersConfig : null),
+  ...workersConfig,
   ...customConfig,
   moduleNameMapper: {
     ...getWorkspaceProjectsAliases({

scripts/jest/src/jest.preset.v8.js

@@ -4,7 +4,6 @@ const path = require('path');
 const { findRepoDeps } = require('@fluentui/scripts-monorepo');
 const { findConfig, merge } = require('@fluentui/scripts-utils');
 
-const { isCI } = require('./environment');
 const { workersConfig } = require('./shared');
 
 const packageJsonPath = findConfig('package.json') ?? '';
@@ -84,7 +83,7 @@ const createConfig = (customConfig = {}) => {
     restoreMocks: true,
     clearMocks: true,
 
-    ...(isCI ? workersConfig : null),
+    ...workersConfig,
 
     watchPlugins: ['jest-watch-typeahead/filename', 'jest-watch-typeahead/testname'],
     // OLD format for migration to jest 29 - TODO: migrate to new format . https://jestjs.io/blog/2022/04/25/jest-28#future

scripts/jest/src/shared.js

@@ -1,3 +1,13 @@
-const workersConfig = { maxWorkers: 4 };
+/**
+ *  **Local Machine:**
+ *
+ * jest is resource greedy. on local machine it will spawn workers into all your CPU threads which will provide additional heat up of your machine and everything else will be blocked.
+ * Based on tests on local machine, 50% of CPU threads is the best value for local development ( also the fastest).
+ *
+ *  **CI:**
+ *
+ * based on testing the same setting is fastest on our CI env atm ( 8 Core machine, 16GB RAM)
+ */
+const workersConfig = { maxWorkers: '50%' };
 
 exports.workersConfig = workersConfig;