diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..a8ad23c
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,36 @@
+name: Test
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+# Cancel in-flight runs for the same ref when a new commit lands.
+concurrency:
+  group: test-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        node-version: ['20', '22']
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: 'npm'
+
+      - run: npm ci
+
+      - name: Build harness
+        run: npm run build:harness
+
+      - name: Run tests
+        run: npm test
diff --git a/package.json b/package.json
index 7067049..74e56e1 100644
--- a/package.json
+++ b/package.json
@@ -13,6 +13,7 @@
     "build:harness": "tsc -p tsconfig.json",
     "harness": "npm run build:harness --silent && node ./dist/cli.js",
     "typecheck": "tsc -p tsconfig.app.json --noEmit",
+    "test": "node --test test/*.mjs",
     "parse-gtfs": "node scripts/parse-gtfs.mjs"
   },
   "engines": {