Add ESM support for JEST tests (#56)

Author: rkoron007

apollo-server/v4/integration-testing/jest.config.cjs

@@ -2,11 +2,14 @@
 module.exports = {
   preset: 'ts-jest',
   testEnvironment: 'node',
+  extensionsToTreatAsEsm: ['.ts'],
+  testPathIgnorePatterns: ['.js'],
   globals: {
     // when we are testing we want to use a slightly different config
     // to allow for jest types
     'ts-jest': {
       tsconfig: '<rootDir>/src/__tests__/tsconfig.json',
+      useESM: true,
     },
   },
 };

apollo-server/v4/integration-testing/package.json

@@ -6,7 +6,7 @@
   "type": "module",
   "license": "MIT",
   "scripts": {
-    "test": "npm run compile && jest",
+    "test": "npm run compile && node --experimental-vm-modules node_modules/jest/bin/jest.js",
     "postinstall": "npm run compile",
     "compile": "tsc",
     "start": "npm run compile && node ./dist/server.js"