Fix Jest tests

Author: alexeyr

jest.config.base.js

@@ -1,19 +1,38 @@
 import { createJsWithTsPreset } from 'ts-jest';
 
+const tsconfig = {
+  // Otherwise we get warnings in tests
+  esModuleInterop: true,
+  // Relative imports in our TS code include `.ts` extensions.
+  // When compiling the package, TS rewrites them to `.js`,
+  // but ts-jest runs on the original code where the `.js` files don't exist,
+  // so this setting needs to be disabled here.
+  rewriteRelativeImportExtensions: false,
+  // Override hybrid module kind (Node16/NodeNext) to avoid ts-jest warning
+  // about requiring isolatedModules: true
+  module: 'ESNext',
+};
+
+const tsJestPreset = createJsWithTsPreset({
+  tsconfig,
+});
+
 // Global Jest configuration for the monorepo
 // Contains common settings that all packages inherit
 export default {
   // === TypeScript Configuration ===
-  // ts-jest preset with custom TypeScript settings
-  ...createJsWithTsPreset({
-    tsconfig: {
-      // Relative imports in our TS code include `.ts` extensions.
-      // When compiling the package, TS rewrites them to `.js`,
-      // but ts-jest runs on the original code where the `.js` files don't exist,
-      // so this setting needs to be disabled here.
-      rewriteRelativeImportExtensions: false,
-    },
-  }),
+  // ts-jest preset with custom TypeScript settings, extended to handle .cts/.mts files
+  ...tsJestPreset,
+  transform: {
+    ...tsJestPreset.transform,
+    // Extend transform to include CommonJS TypeScript (.cts) and ES Module TypeScript (.mts) files
+    '^.+\\.[cm]?ts$': [
+      'ts-jest',
+      {
+        tsconfig,
+      },
+    ],
+  },
 
   // === Test Environment Configuration ===
   testEnvironment: 'jsdom',
@@ -23,5 +42,6 @@ export default {
   testMatch: ['**/?(*.)+(spec|test).[jt]s?(x)'],
 
   // === Common Module File Extensions ===
-  moduleFileExtensions: ['js', 'jsx', 'ts', 'tsx', 'json'],
+  // Include cts/mts for CommonJS/ES module TypeScript files
+  moduleFileExtensions: ['js', 'jsx', 'ts', 'tsx', 'cts', 'mts', 'json'],
 };