test: Improve Kitchen Test Logging (#1914)

* test: Improve Kitchen Test Logging

- Adds missing STDERR logging for improved debugging, which was missing for a while
- Removes `execa`, as it is unneeded and outdated

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* fix: add 'error' event handle

* test: documentation

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

README.md

@@ -1041,19 +1041,19 @@ class CustomSupplier implements SubjectTokenSupplier {
 }
 
 const clientOptions = {
-  audience: '//iam.googleapis.com/locations/global/workforcePools/$WORKLOAD_POOL_ID/providers/$PROVIDER_ID', // Set the GCP audience.
+  audience: '//iam.googleapis.com/locations/global/workforcePools/$WORKFORCE_POOL_ID/providers/$PROVIDER_ID', // Set the GCP audience.
   subject_token_type: 'urn:ietf:params:oauth:token-type:id_token', // Set the subject token type.
   subject_token_supplier: new CustomSupplier() // Set the custom supplier.
 }
 
 const client = new CustomSupplier(clientOptions);
 ```
 
-Where the audience is: `//iam.googleapis.com/locations/global/workforcePools/$WORKLOAD_POOL_ID/providers/$PROVIDER_ID`
+Where the audience is: `//iam.googleapis.com/locations/global/workforcePools/$WORKFORCE_POOL_ID/providers/$PROVIDER_ID`
 
 Where the following variables need to be substituted:
 
-* `WORKFORCE_POOL_ID`: The worforce pool ID.
+* `$WORKFORCE_POOL_ID`: The worforce pool ID.
 * `$PROVIDER_ID`: The provider ID.
 
 and the workforce pool user project is the project number associated with the [workforce pools user project](https://cloud.google.com/iam/docs/workforce-identity-federation#workforce-pools-user-project).

package.json

@@ -38,7 +38,6 @@
     "chai": "^4.2.0",
     "cheerio": "1.0.0-rc.12",
     "codecov": "^3.0.2",
-    "execa": "^5.0.0",
     "gts": "^5.0.0",
     "is-docker": "^2.0.0",
     "jsdoc": "^4.0.0",

system-test/test.kitchen.ts

@@ -14,13 +14,13 @@
 
 import * as assert from 'assert';
 import {describe, it, afterEach} from 'mocha';
-import * as execa from 'execa';
 import * as fs from 'fs';
 import * as mv from 'mv';
 import {ncp} from 'ncp';
 import * as os from 'os';
 import * as path from 'path';
 import {promisify} from 'util';
+import {spawn} from 'child_process';
 
 const mvp = promisify(mv) as {} as (...args: string[]) => Promise<void>;
 const ncpp = promisify(ncp);
@@ -29,18 +29,39 @@ const keep = !!process.env.GALN_KEEP_TEMPDIRS;
 const pkg = require('../../package.json');
 
 let stagingDir: string;
+
+/**
+ * Spawns and runs a command asynchronously.
+ *
+ * @param params params to pass to {@link spawn}
+ */
+async function run(...params: Parameters<typeof spawn>) {
+  const command = spawn(...params);
+
+  await new Promise<void>((resolve, reject) => {
+    // Unlike `exec`/`execFile`, this keeps the order of STDOUT/STDERR in case they were interweaved;
+    // making it easier to debug and follow along.
+    command.stdout?.on('data', console.log);
+    command.stderr?.on('data', console.error);
+    command.on('close', (code, signal) => {
+      return code === 0 ? resolve() : reject({code, signal});
+    });
+    command.on('error', reject);
+  });
+}
+
 async function packAndInstall() {
   stagingDir = await fs.promises.mkdtemp(
     path.join(os.tmpdir(), 'google-auth-library-nodejs-pack-')
   );
 
-  await execa('npm', ['pack'], {stdio: 'inherit'});
+  await run('npm', ['pack'], {});
   const tarball = `${pkg.name}-${pkg.version}.tgz`;
   // stagingPath can be on another filesystem so fs.rename() will fail
   // with EXDEV, hence we use `mv` module here.
   await mvp(tarball, `${stagingDir}/google-auth-library.tgz`);
   await ncpp('system-test/fixtures/kitchen', `${stagingDir}/`);
-  await execa('npm', ['install'], {cwd: `${stagingDir}/`, stdio: 'inherit'});
+  await run('npm', ['install'], {cwd: `${stagingDir}/`});
 }
 
 describe('pack and install', () => {
@@ -61,10 +82,10 @@ describe('pack and install', () => {
     this.timeout(40000);
     await packAndInstall();
     // we expect npm install is executed in the before hook
-    await execa('npx', ['webpack'], {cwd: `${stagingDir}/`, stdio: 'inherit'});
+    await run('npx', ['webpack'], {cwd: `${stagingDir}/`});
     const bundle = path.join(stagingDir, 'dist', 'bundle.min.js');
     // ensure it is a non-empty bundle
-    assert(fs.statSync(bundle).size);
+    assert(fs.statSync(bundle).size, 'Size should not be empty');
   });
 
   /**