aws · mergify · Nov 25, 2024 · Nov 25, 2024 · Nov 25, 2024 · Nov 25, 2024
@@ -20,6 +20,5 @@ module.exports = {
 
     // We have many tests here that commonly time out
     testTimeout: 30_000,
-    // These tests are too chatty. Shush.
-    silent: true,
+    setupFilesAfterEnv: ["<rootDir>/test/jest-setup-after-env.ts"],
 };
@@ -1,4 +1,6 @@
 import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
 import { Writable } from 'stream';
 import { StringDecoder } from 'string_decoder';
 import * as cxschema from '@aws-cdk/cloud-assembly-schema';
@@ -12,6 +14,22 @@ import { CdkToolkit } from '../lib/cdk-toolkit';
 let cloudExecutable: MockCloudExecutable;
 let cloudFormation: jest.Mocked<Deployments>;
 let toolkit: CdkToolkit;
+let oldDir: string;
+let tmpDir: string;
+
+beforeAll(() => {
+  // The toolkit writes and checks for temporary files in the current directory,
+  // so run these tests in a tempdir so they don't interfere with each other
+  // and other tests.
+  oldDir = process.cwd();
+  tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'aws-cdk-test'));
+  process.chdir(tmpDir);
+});
+
+afterAll(() => {
+  process.chdir(oldDir);
+  fs.rmSync(tmpDir, { recursive: true, force: true });
+});
 
 describe('fixed template', () => {
   const templatePath = 'oldTemplate.json';

@@ -0,0 +1,64 @@
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+
+/**
+ * Global test setup for Jest tests
+ *
+ * It's easy to accidentally write tests that interfere with each other by
+ * writing files to disk in the "current directory". To prevent this, the global
+ * test setup creates a directory in the temporary directory and chmods it to
+ * being non-writable. That way, whenever a test tries to write to the current
+ * directory, it will produce an error and we'll be able to find and fix the
+ * test.
+ *
+ * If you see `EACCES: permission denied`, you have a test that creates files
+ * in the current directory, and you should be sure to do it in a temporary
+ * directory that you clean up afterwards.
+ *
+ * ## Alternate approach
+ *
+ * I tried an approach where I would automatically try to create and clean up
+ * temp directories for every test, but it was introducing too many conflicts
+ * with existing test behavior (around specific ordering of temp directory
+ * creation and cleanup tasks that are already present) in many places that I
+ * didn't want to go and chase down.
+ *
+ */
+
+let tmpDir: string;
+let oldDir: string;
+
+beforeAll(() => {
+  tmpDir = path.join(os.tmpdir(), 'cdk-nonwritable');
+  if (!fs.existsSync(tmpDir)) {
+    fs.mkdirSync(tmpDir);
+    fs.chmodSync(tmpDir, 0o500);
+  }
+  oldDir = process.cwd();
+  process.chdir(tmpDir);
+  tmpDir = process.cwd(); // This will have resolved symlinks
+});
+
+/**
+ * We need a cleanup here
+ *
+ * 99% of the time, Jest runs the tests in a subprocess and this isn't
+ * necessary because we would have `chdir`ed in the subprocess.
+ *
+ * But sometimes we ask Jest with `-i` to run the tests in the main process,
+ * or if you only ask for a single test suite Jest runs the tests in the main
+ * process, and then we `chdir`ed the main process away.
+ *
+ * Jest will then try to write the `coverage` directory to the readonly directory,
+ * and fail. Chdir back to the original dir.
+ *
+ * Only if we are still in the tempdir, because if not then some other temporary
+ * directory cleanup block has already done the same and we shouldn't interfere
+ * with that.
+ */
+afterAll(() => {
+  if (process.cwd() === tmpDir) {
+    process.chdir(oldDir);
+  }
+});
@@ -455,23 +455,20 @@ describe(CachedDataSource, () => {
   });
 
   test('retrieves data from the delegate when the file cannot be read', async () => {
-    const debugSpy = jest.spyOn(logging, 'debug');
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'cdk-test'));
+    try {
+      const debugSpy = jest.spyOn(logging, 'debug');
 
-    if (fs.existsSync('does-not-exist.json')) {
-      fs.unlinkSync('does-not-exist.json');
-    }
-
-    const dataSource = dataSourceWithDelegateReturning(freshData, 'does-not-exist.json');
+      const dataSource = dataSourceWithDelegateReturning(freshData, `${tmpDir}/does-not-exist.json`);
 
-    const notices = await dataSource.fetch();
-
-    expect(notices).toEqual(freshData);
-    expect(debugSpy).not.toHaveBeenCalled();
+      const notices = await dataSource.fetch();
 
-    debugSpy.mockRestore();
+      expect(notices).toEqual(freshData);
+      expect(debugSpy).not.toHaveBeenCalled();
 
-    if (fs.existsSync('does-not-exist.json')) {
-      fs.unlinkSync('does-not-exist.json');
+      debugSpy.mockRestore();
+    } finally {
+      fs.rmSync(tmpDir, { recursive: true, force: true });
     }
   });