diff --git a/.github/workflows/branches.yml b/.github/workflows/branches.yml
index 8e594df..799ced0 100644
--- a/.github/workflows/branches.yml
+++ b/.github/workflows/branches.yml
@@ -37,3 +37,15 @@ jobs:
       working-directory: ./webpack
     - run: yarn test
       working-directory: ./webpack
+    - run: yarn
+      working-directory: ./cjs-test
+    - run: yarn build
+      working-directory: ./cjs-test
+    - run: yarn test
+      working-directory: ./cjs-test
+    - run: yarn
+      working-directory: ./esm-test
+    - run: yarn build
+      working-directory: ./esm-test
+    - run: yarn test
+      working-directory: ./esm-test
diff --git a/.github/workflows/master.yml b/.github/workflows/master.yml
index 756a2de..62edb51 100644
--- a/.github/workflows/master.yml
+++ b/.github/workflows/master.yml
@@ -36,6 +36,18 @@ jobs:
       working-directory: ./webpack
     - run: yarn test
       working-directory: ./webpack
+    - run: yarn
+      working-directory: ./cjs-test
+    - run: yarn build
+      working-directory: ./cjs-test
+    - run: yarn test
+      working-directory: ./cjs-test
+    - run: yarn
+      working-directory: ./esm-test
+    - run: yarn build
+      working-directory: ./esm-test
+    - run: yarn test
+      working-directory: ./esm-test
 
   release:
     name: Release
diff --git a/cjs-test/jest.config.mjs b/cjs-test/jest.config.mjs
new file mode 100644
index 0000000..14edfa3
--- /dev/null
+++ b/cjs-test/jest.config.mjs
@@ -0,0 +1,10 @@
+export default {
+	preset: 'ts-jest',
+	testEnvironment: 'node',
+	testMatch: [
+		'<rootDir>/test/**/*.ts',
+		'<rootDir>/test/**/*.js',
+	],
+	modulePathIgnorePatterns: [],
+	collectCoverage: false,
+}
diff --git a/cjs-test/package.json b/cjs-test/package.json
new file mode 100644
index 0000000..1eb8a19
--- /dev/null
+++ b/cjs-test/package.json
@@ -0,0 +1,28 @@
+{
+  "name": "awesome-phonenumber-test",
+  "license": "MIT",
+  "author": "Gustaf Räntilä <g.rantila@gmail.com>",
+  "engines": {
+    "node": ">=12"
+  },
+  "main": "./index.js",
+  "types": "./index.d.ts",
+  "type": "commonjs",
+  "scripts": {
+    "postinstall:lib": "cd node_modules && ln -s ../.. awesome-phonenumber || true",
+    "postinstall:tests": "cp ../test/awesome-phonenumber/*.ts test",
+    "postinstall": "yarn postinstall:lib && yarn postinstall:tests",
+    "build": "tsc -p .",
+    "test": "jest"
+  },
+  "devDependencies": {
+    "@babel/preset-env": "^7.17.10",
+    "@babel/preset-typescript": "^7.16.7",
+    "@types/jest": "^27.5.0",
+    "jest": "^28.1.0",
+    "ts-jest": "^28.0.2",
+    "ts-jest-resolver": "^2.0.0",
+    "ts-node": "^10.7.0",
+    "typescript": "^4.6.4"
+  }
+}
diff --git a/cjs-test/test/.gitkeep b/cjs-test/test/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/cjs-test/tsconfig.json b/cjs-test/tsconfig.json
new file mode 100644
index 0000000..6c981d1
--- /dev/null
+++ b/cjs-test/tsconfig.json
@@ -0,0 +1,13 @@
+{
+	"compilerOptions": {
+		"baseUrl": ".",
+		"lib": [ "es2019", "dom" ],
+		"moduleResolution": "node",
+		"module": "CommonJS",
+		"target": "es5",
+		"allowSyntheticDefaultImports": true
+	},
+	"include": [
+		"test"
+	]
+}
diff --git a/esm-test/babel.config.cjs b/esm-test/babel.config.cjs
new file mode 120000
index 0000000..57a080f
--- /dev/null
+++ b/esm-test/babel.config.cjs
@@ -0,0 +1 @@
+../babel.config.cjs
\ No newline at end of file
diff --git a/esm-test/jest.config.mjs b/esm-test/jest.config.mjs
new file mode 100644
index 0000000..e587f51
--- /dev/null
+++ b/esm-test/jest.config.mjs
@@ -0,0 +1,11 @@
+export default {
+	resolver: 'ts-jest-resolver',
+	testEnvironment: 'node',
+	testMatch: [
+		'<rootDir>/test/**/*.ts',
+		'<rootDir>/test/**/*.js',
+	],
+	modulePathIgnorePatterns: [],
+	collectCoverage: false,
+	extensionsToTreatAsEsm: ['.ts'],
+}
diff --git a/esm-test/package.json b/esm-test/package.json
new file mode 100644
index 0000000..d156b6c
--- /dev/null
+++ b/esm-test/package.json
@@ -0,0 +1,27 @@
+{
+  "name": "awesome-phonenumber-test",
+  "license": "MIT",
+  "author": "Gustaf Räntilä <g.rantila@gmail.com>",
+  "engines": {
+    "node": ">=12"
+  },
+  "main": "./index.js",
+  "types": "./index.d.ts",
+  "type": "module",
+  "scripts": {
+    "postinstall:lib": "cd node_modules && ln -s ../.. awesome-phonenumber || true",
+    "postinstall:tests": "cp ../test/awesome-phonenumber/*.ts test",
+    "postinstall": "yarn postinstall:lib && yarn postinstall:tests",
+    "build": "tsc -p .",
+    "test": "NODE_OPTIONS=--experimental-vm-modules jest"
+  },
+  "devDependencies": {
+    "@babel/preset-env": "^7.17.10",
+    "@babel/preset-typescript": "^7.16.7",
+    "@types/jest": "^27.5.0",
+    "jest": "^28.1.0",
+    "ts-jest-resolver": "^2.0.0",
+    "ts-node": "^10.7.0",
+    "typescript": "^4.6.4"
+  }
+}
diff --git a/esm-test/test/.gitkeep b/esm-test/test/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/esm-test/tsconfig.json b/esm-test/tsconfig.json
new file mode 100644
index 0000000..77920b1
--- /dev/null
+++ b/esm-test/tsconfig.json
@@ -0,0 +1,12 @@
+{
+	"compilerOptions": {
+		"baseUrl": ".",
+		"lib": [ "es2019", "dom" ],
+		"moduleResolution": "node",
+		"target": "ESNext",
+		"allowSyntheticDefaultImports": true
+	},
+	"include": [
+		"test"
+	]
+}