Jest transform workaround for ESM-only packages

Enables Babel transform for ESM-only packages (to CommonJS) until Jest supports ESM https://jestjs.io/docs/ecmascript-modules
alphagov · Nov 18, 2022 · b6767cb · b6767cb
1 parent 8f4061e
commit b6767cb
Showing 1 changed file with 28 additions and 3 deletions.
diff --git a/jest.config.js b/jest.config.js
@@ -14,7 +14,23 @@ const config = {
   // See: https://jestjs.io/docs/ecmascript-modules
   transform: {
     '^.+\\.m?js$': ['babel-jest', { rootMode: 'upward' }]
-  }
+  },
+
+  // Enable Babel transforms for ESM-only node_modules
+  transformIgnorePatterns: [`<rootDir>/node_modules/(?!(${[
+    'del',
+    'slash',
+
+    // Including child dependencies
+    'aggregate-error',
+    'clean-stack',
+    'escape-string-regexp',
+    'globby',
+    'indent-string',
+    'is-path-cwd',
+    'is-path-inside',
+    'p-map'
+  ].join('|')})/)`]
 }
 
 module.exports = {
@@ -25,7 +41,10 @@ module.exports = {
       displayName: 'Gulp tasks',
       testMatch: [
         '**/gulp/**/*.test.{js,mjs}'
-      ]
+      ],
+
+      // No additional transforms needed
+      transformIgnorePatterns: ['<rootDir>/node_modules/']
     },
     {
       ...config,
@@ -37,7 +56,10 @@ module.exports = {
       testEnvironment: './config/jest/environment/jsdom.mjs',
       testMatch: [
         '**/(*.)?template.test.{js,mjs}'
-      ]
+      ],
+
+      // No additional transforms needed
+      transformIgnorePatterns: ['<rootDir>/node_modules/']
     },
     {
       ...config,
@@ -63,6 +85,9 @@ module.exports = {
         '!**/gulp/**'
       ],
 
+      // No additional transforms needed
+      transformIgnorePatterns: ['<rootDir>/node_modules/'],
+
       // Web server required
       globalSetup: './config/jest/server/start.mjs',
       globalTeardown: './config/jest/server/stop.mjs'