test: add memory leak test

.gitignore

@@ -20,3 +20,4 @@ msw-*.tgz
 /examples
 /test/modules/node/node-esm-tests
 *.vitest-temp.json
+*.heapprofile

test/node/performance/generate-heapmap.js

@@ -0,0 +1,18 @@
+import { spawnSync } from 'node:child_process'
+
+spawnSync('node', [new URL('./memory-usage.js', import.meta.url).pathname], {
+  stdio: 'inherit',
+  env: {
+    ...process.env,
+    NODE_OPTIONS: `--expose-gc --heap-prof --heap-prof-dir=${new URL('.', import.meta.url).pathname} --heap-prof-name=${Date.now()}-msw.heapprofile`,
+  },
+})
+
+spawnSync('node', [new URL('./memory-usage.js', import.meta.url).pathname], {
+  stdio: 'inherit',
+  env: {
+    ...process.env,
+    USE_NODE: 1,
+    NODE_OPTIONS: `--expose-gc --heap-prof --heap-prof-dir=${new URL('.', import.meta.url).pathname} --heap-prof-name=${Date.now()}-node.heapprofile`,
+  },
+})

test/node/performance/memory-usage.js

@@ -0,0 +1,40 @@
+import http from 'node:http'
+import { setupServer } from 'msw/node'
+
+async function profile() {
+  const startMemoryUsage = process.memoryUsage().heapUsed
+
+  for (let i = 0; i < 10_000; i++) {
+    let server
+
+    if (!process.env.USE_NODE) {
+      server = setupServer()
+      server.listen({ onUnhandledRequest: 'bypass' })
+    }
+
+    await new Promise((resolve) => {
+      http
+        .get('http://localhost/non-existent', () => resolve())
+        .on('error', () => resolve())
+    })
+
+    if (!process.env.USE_NODE) {
+      server.close()
+    }
+  }
+
+  const endMemoryUsage = process.memoryUsage().heapUsed
+  const memoryUsed = (endMemoryUsage - startMemoryUsage) / 1024 / 1024
+
+  console.log(
+    'Memory used:',
+    memoryUsed,
+    'MB',
+    process.env.USE_NODE ? '(Node.js)' : '(MSW)',
+  )
+
+  global.gc?.()
+  process.send?.(memoryUsed)
+}
+
+profile()

test/node/performance/memory-usage.test.ts

@@ -0,0 +1,24 @@
+import { spawn } from 'node:child_process'
+import { DeferredPromise } from '@open-draft/deferred-promise'
+
+it('does not leak memory when handling a large number of requests', async () => {
+  // Spawn the memory consumption scenario in a child process
+  // so the test runner's memory consumption does not affect the results.
+  const child = spawn(
+    'node',
+    [new URL('./memory-usage.js', import.meta.url).pathname, '--expose-gc'],
+    {
+      stdio: ['inherit', 'inherit', 'inherit', 'ipc'],
+    },
+  )
+
+  const memoryUsedPromise = new DeferredPromise<number>()
+  child.on('message', (message) => {
+    if (typeof message === 'number') {
+      memoryUsedPromise.resolve(message)
+    }
+  })
+  const memoryUsed = await memoryUsedPromise
+
+  expect(memoryUsed).toBeLessThan(8)
+})