Demonstrate coverage annotations for Docker containers

.dockerignore

@@ -1 +1,2 @@
-node_modules/
+node_modules/
+report.json

.github/workflows/test.yml

@@ -13,7 +13,18 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Start containers
-        run: docker compose up -d
+        run: docker compose -f docker-compose.ci.yml up -d
+
+      # install any dependencies since this is a fresh checkout
+      - name: Install dependencies
+        run: docker compose -f docker-compose.ci.yml run -v ${GITHUB_WORKSPACE}:${GITHUB_WORKSPACE} --workdir ${GITHUB_WORKSPACE} tests yarn install
 
       - name: Run tests
-        run: docker compose run tests jest --coverage
+        run: docker compose -f docker-compose.ci.yml run -v ${GITHUB_WORKSPACE}:${GITHUB_WORKSPACE} --workdir ${GITHUB_WORKSPACE} tests jest --coverage --ci --json --testLocationInResults --outputFile=report.json
+
+      - name: Collect test coverage
+        uses: ArtiomTr/jest-coverage-report-action@v2
+        if: always() # we should still try to run this even if there are test failures
+        with:
+          coverage-file: ./report.json
+          base-coverage-file: ./report.json

.gitignore

@@ -1 +1,2 @@
-node_modules/
+node_modules/
+report.json

docker-compose.ci.yml

@@ -0,0 +1,7 @@
+services:
+  tests:
+    extends:
+      file: "docker-compose.yml"
+      service: tests
+    build:
+      target: base # do not install dependencies because we will mount a fresh checkout

sum.js

@@ -1,4 +1,9 @@
 function sum(a, b) {
   return a + b;
 }
-module.exports = sum;
+
+function multiply(a, b) {
+  return a * b;
+}
+
+module.exports = sum;

sum.test.js

@@ -2,4 +2,8 @@
 
 test('adds 1 + 2 to equal 3', () => {
   expect(sum(1, 2)).toBe(3);
-});
+});
+
+test('adds 1 + 2 to equal 4', () => {
+  expect(sum(1, 2)).toBe(4);
+});