test: test maxConcurrency

packages/runner/src/run.ts

@@ -311,7 +311,6 @@ export async function runSuite(suite: Suite, runner: VitestRunner) {
       else {
         for (let tasksGroup of partitionSuiteChildren(suite)) {
           if (tasksGroup[0].concurrent === true) {
-            // TODO: p-limit needs to be shared globally to not go over maxConcurrency?
             const mutex = limit(runner.config.maxConcurrency)
             await Promise.all(tasksGroup.map(c => mutex(() => runSuiteChild(c, runner))))
           }

test/core/test/concurrent-maxConcurrency.test.ts

@@ -0,0 +1,42 @@
+import { createDefer } from '@vitest/utils'
+import { describe, test, vi } from 'vitest'
+
+vi.setConfig({ maxConcurrency: 2 })
+
+describe('limit for each suite', () => {
+  // this test requires running 3 tests in parallel.
+  // but, currently p-limit is applied for each suite layer,
+  // so tests succeed.
+  //
+  //  [0]  [1]  [2]
+  //   * ->
+  //        * ->
+  //          <- *
+  //     <------
+
+  const defers = [
+    createDefer<void>(),
+    createDefer<void>(),
+    createDefer<void>(),
+  ]
+
+  describe('1st suite', { concurrent: true, concurrentSuite: true }, () => {
+    test('a', async () => {
+      defers[0].resolve()
+      await defers[2]
+    })
+
+    test('b', async () => {
+      await defers[0]
+      defers[1].resolve()
+      await defers[2]
+    })
+  })
+
+  describe('2nd suite', { concurrent: true, concurrentSuite: true }, () => {
+    test('c', async () => {
+      await defers[1]
+      defers[2].resolve()
+    })
+  })
+})

test/core/test/concurrent-suite.test.ts

@@ -129,37 +129,3 @@ describe('tests are sequential', () => {
     })
   })
 })
-
-// TODO
-describe('maxConcurrency', { concurrent: true, concurrentSuite: true }, () => {
-  const defers = [
-    createDefer<void>(),
-    createDefer<void>(),
-    createDefer<void>(),
-    createDefer<void>(),
-  ]
-
-  describe('1st suite', () => {
-    test('0', async () => {
-      defers[0].resolve()
-      await defers[3]
-    })
-
-    test('1', async () => {
-      await defers[0]
-      defers[1].resolve()
-    })
-  })
-
-  describe('2nd suite', () => {
-    test('2', async () => {
-      await defers[1]
-      defers[2].resolve()
-    })
-
-    test('3', async () => {
-      await defers[2]
-      defers[3].resolve()
-    })
-  })
-})