fix(coverage): @vitest/web-worker with v8 coverage

test/coverage-test/fixtures/src/worker-wrapper.ts

@@ -0,0 +1,24 @@
+export async function calcInBackground(arg: number) {
+  const worker = new Worker(new URL('./worker', import.meta.url), {
+    type: 'module',
+  });
+
+  const cleanup = () => {
+    worker.terminate();
+  };
+
+  let doResolve: ((arg: number) => void) | undefined = undefined;
+  const resultPromise = new Promise<number>((resolve) => {
+    doResolve = resolve;
+  });
+
+  worker.onmessage = (ev: MessageEvent<number>) => {
+    doResolve!(ev.data);
+  };
+
+  worker.postMessage(arg);
+
+  const result = await resultPromise;
+  cleanup();
+  return result;
+}

test/coverage-test/fixtures/src/worker.ts

@@ -0,0 +1,29 @@
+self.onmessage = (ev: MessageEvent<number>) => {
+  const start = performance.now();
+  let data = ev.data;
+  if (data === 5) {
+    uncovered()
+    throw new Error("uncovered");
+  }
+
+  if(data === 6) {
+    uncovered()
+    throw new Error("uncovered");
+
+  }
+
+  while (data > 9) {
+    data -= 1;
+  }
+
+  const result = doCalc(data);
+  postMessage(result);
+};
+
+function uncovered() {
+  return "This is uncovered"
+}
+
+function doCalc(arg: number) {
+  return arg * 2;
+}

test/coverage-test/fixtures/test/web-worker.ts

@@ -0,0 +1,7 @@
+import { expect, test } from 'vitest';
+import { calcInBackground } from '../src/worker-wrapper';
+
+test('worker', async () => {
+  const result = await calcInBackground(45);
+  expect(result).toBe(18);
+});

test/coverage-test/package.json

@@ -14,6 +14,7 @@
     "@vitest/browser": "workspace:*",
     "@vitest/coverage-istanbul": "workspace:*",
     "@vitest/coverage-v8": "workspace:*",
+    "@vitest/web-worker": "workspace:*",
     "@vue/test-utils": "latest",
     "happy-dom": "latest",
     "istanbul-lib-coverage": "^3.2.0",

test/coverage-test/test/web-worker.test.ts

@@ -0,0 +1,79 @@
+import { expect } from 'vitest'
+import { isV8Provider, readCoverageMap, runVitest, test } from '../utils'
+
+test('web worker coverage is correct', async () => {
+  await runVitest({
+    setupFiles: ['@vitest/web-worker'],
+    include: ['fixtures/test/web-worker.ts'],
+    environment: 'jsdom',
+    coverage: {
+      include: ['fixtures/src/worker.ts'],
+      reporter: 'json',
+    },
+  })
+
+  const coverageMap = await readCoverageMap()
+  const fileCoverage = coverageMap.fileCoverageFor('<process-cwd>/fixtures/src/worker.ts')
+  const summary = fileCoverage.toSummary()
+
+  if (isV8Provider()) {
+    expect(summary).toMatchInlineSnapshot(`
+      {
+        "branches": {
+          "covered": 3,
+          "pct": 60,
+          "skipped": 0,
+          "total": 5,
+        },
+        "functions": {
+          "covered": 2,
+          "pct": 66.66,
+          "skipped": 0,
+          "total": 3,
+        },
+        "lines": {
+          "covered": 14,
+          "pct": 60.86,
+          "skipped": 0,
+          "total": 23,
+        },
+        "statements": {
+          "covered": 14,
+          "pct": 60.86,
+          "skipped": 0,
+          "total": 23,
+        },
+      }
+    `)
+  }
+  else {
+    expect(summary).toMatchInlineSnapshot(`
+      {
+        "branches": {
+          "covered": 2,
+          "pct": 50,
+          "skipped": 0,
+          "total": 4,
+        },
+        "functions": {
+          "covered": 2,
+          "pct": 66.66,
+          "skipped": 0,
+          "total": 3,
+        },
+        "lines": {
+          "covered": 10,
+          "pct": 66.66,
+          "skipped": 0,
+          "total": 15,
+        },
+        "statements": {
+          "covered": 10,
+          "pct": 66.66,
+          "skipped": 0,
+          "total": 15,
+        },
+      }
+    `)
+  }
+})