Support TypeScript user code (#24)

Author: davidjgoss

CHANGELOG.md

@@ -6,10 +6,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- Support TypeScript user code ([#24](https://github.com/cucumber/cucumber-node/pull/24))
 
 ## [0.1.0] - 2025-02-18
 ### Added
 - Initial release
 
 [Unreleased]: https://github.com/cucumber/cucumber-node/compare/0.1.0...HEAD
-[0.1.0]: https://github.com/cucumber/cucumber-node/compare/2d5d66e...0.1.0
+[0.1.0]: https://github.com/cucumber/cucumber-node/compare/2d5d66e...0.1.0

README.md

@@ -100,11 +100,20 @@ When you write a step or hook function, the first argument will always be a [`Te
 Discovery of your code is based on the following glob (relative to the working directory):
 
 ```
-features/**/*.{cjs,js,mjs}
+features/**/*.{cjs,js,mjs,cts,mts,ts}
 ```
 
 This isn't configurable ([yet](https://github.com/cucumber/cucumber-node/issues/10)).
 
+### TypeScript
+
+You can write your code in TypeScript. Depending on your project, you might either:
+
+1. Just rely on Node.js built-in type stripping without any other dependencies or configuration
+2. Use [tsx](https://www.npmjs.com/package/tsx) to transpile by adding `--import tsx` to your test command
+
+See https://nodejs.org/api/typescript.html for more details.
+
 ## Reporters
 
 Some Cucumber formatters are included as Node.js test reporters:

src/runner/loadSupport.ts

@@ -6,7 +6,7 @@ import { builder } from './state.js'
 import { SupportCodeLibrary } from './SupportCodeLibrary.js'
 
 export async function loadSupport(): Promise<SupportCodeLibrary> {
-  const paths = await globby('features/**/*.{cjs,js,mjs}')
+  const paths = await globby('features/**/*.{cjs,js,mjs,cts,mts,ts}')
   for (const path of paths) {
     await import(pathToFileURL(path).toString())
   }

test/cck/cck.spec.ts

@@ -57,7 +57,7 @@ describe('Cucumber Compatibility Kit',  () => {
         return this.skip()
       }
 
-      const harness = await makeTestHarness('cck')
+      const harness = await makeTestHarness()
 
       await harness.copyDir(path.join(
         process.cwd(),

test/integration/modules.spec.ts

@@ -0,0 +1,28 @@
+import { stripVTControlCharacters } from 'node:util'
+import { expect } from 'chai'
+import { makeTestHarness } from '../utils.js'
+
+describe('Modules', () => {
+  it('handles TypeScript code via type stripping', async () => {
+    const harness = await makeTestHarness()
+    await harness.writeFile(
+      'features/first.feature',
+      `Feature:
+  Scenario:
+    Given a step
+    `
+    )
+    await harness.writeFile(
+      'features/steps.ts',
+      `import { Given } from '@cucumber/node'
+import type { TestCaseContext } from '@cucumber/node'
+Given('a step', (t: TestCaseContext) => {
+  t.assert.strictEqual(2, 2)
+})
+    `
+    )
+    const [output] = await harness.run('spec', '--experimental-strip-types')
+    const sanitised = stripVTControlCharacters(output.trim())
+    expect(sanitised).to.include('ℹ pass 2')
+  })
+})

test/integration/reporters.spec.ts

@@ -5,7 +5,7 @@ import path from 'node:path'
 
 describe('Reporters', () => {
   it('does not emit messages as diagnostics if no cucumber reporters', async () => {
-    const harness = await makeTestHarness('reporters')
+    const harness = await makeTestHarness()
     await harness.writeFile(
       'features/first.feature',
       `Feature:
@@ -25,7 +25,7 @@ describe('Reporters', () => {
   })
 
   it('provides a useful error for an ambiguous step', async () => {
-    const harness = await makeTestHarness('reporters')
+    const harness = await makeTestHarness()
     await harness.writeFile(
       'features/first.feature',
       `Feature:
@@ -44,7 +44,7 @@ Given('a step', () => {})`)
   })
 
   it('provides a useful error for an undefined step', async () => {
-    const harness = await makeTestHarness('reporters')
+    const harness = await makeTestHarness()
     await harness.writeFile(
       'features/first.feature',
       `Feature:

test/utils.ts

@@ -52,9 +52,9 @@ class TestHarness {
   }
 }
 
-export async function makeTestHarness(prefix: string) {
+export async function makeTestHarness() {
   // create temporary directory
-  const tempDir = await mkdtemp(path.join(tmpdir(), `cucumber-node-${prefix}-`))
+  const tempDir = await mkdtemp(path.join(tmpdir(), `cucumber-node-integration-`))
 
   // symlink @cucumber/node package into node_modules
   await mkdir(path.join(tempDir, 'features'))