feature: allow ESM for test environment

CHANGELOG.md

@@ -21,6 +21,7 @@
 - `[jest-transform]` Pass config options defined in Jest's config to transformer's `process` and `getCacheKey` functions ([#10926](https://github.com/facebook/jest/pull/10926))
 - `[jest-worker]` Add support for custom task queues and adds a `PriorityQueue` implementation. ([#10921](https://github.com/facebook/jest/pull/10921))
 - `[jest-worker]` Add in-order scheduling policy to jest worker ([10902](https://github.com/facebook/jest/pull/10902))
+- `[jest-runner]` Possibility to use ESM for test environment ([11033](https://github.com/facebook/jest/pull/11033))
 
 ### Fixes
 

packages/jest-runner/src/runTest.ts

@@ -6,6 +6,7 @@
  *
  */
 
+import {pathToFileURL} from 'url';
 import chalk = require('chalk');
 import * as fs from 'graceful-fs';
 import sourcemapSupport = require('source-map-support');
@@ -104,9 +105,35 @@ async function runTestInternal(
   }
 
   const transformer = new ScriptTransformer(config);
-  const TestEnvironment: typeof JestEnvironment = interopRequireDefault(
-    transformer.requireAndTranspileModule(testEnvironment),
-  ).default;
+  let TestEnvironment: typeof JestEnvironment;
+  try {
+    TestEnvironment = interopRequireDefault(
+      transformer.requireAndTranspileModule(testEnvironment),
+    ).default;
+  } catch (err) {
+    try {
+      const configUrl = pathToFileURL(testEnvironment);
+
+      // node `import()` supports URL, but TypeScript doesn't know that
+      const importedConfig = await import(configUrl.href);
+
+      if (!importedConfig.default) {
+        throw new Error(
+          `Jest: Failed to load mjs config file ${testEnvironment} - did you use a default export?`,
+        );
+      }
+
+      TestEnvironment = importedConfig.default;
+    } catch (innerError) {
+      if (innerError.message === 'Not supported') {
+        throw new Error(
+          `Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file ${testEnvironment}`,
+        );
+      }
+
+      throw innerError;
+    }
+  }
   const testFramework: TestFramework = interopRequireDefault(
     transformer.requireAndTranspileModule(
       process.env.JEST_JASMINE === '1' ? 'jest-jasmine2' : config.testRunner,