fix incomplete coverage reports on macos (microsoft#212639)

* eng: fix incomplete coverage reports on macos

Wait for stdout to drain before exiting

* better fix

Author: connor4312

test/unit/electron/index.js

@@ -315,14 +315,18 @@ app.on('ready', () => {
 		}
 	});
 
+	const reporters = [];
+
 	if (args.tfs) {
-		new mocha.reporters.Spec(runner);
-		new MochaJUnitReporter(runner, {
-			reporterOptions: {
-				testsuitesTitle: `${args.tfs} ${process.platform}`,
-				mochaFile: process.env.BUILD_ARTIFACTSTAGINGDIRECTORY ? path.join(process.env.BUILD_ARTIFACTSTAGINGDIRECTORY, `test-results/${process.platform}-${process.arch}-${args.tfs.toLowerCase().replace(/[^\w]/g, '-')}-results.xml`) : undefined
-			}
-		});
+		reporters.push(
+			new mocha.reporters.Spec(runner),
+			new MochaJUnitReporter(runner, {
+				reporterOptions: {
+					testsuitesTitle: `${args.tfs} ${process.platform}`,
+					mochaFile: process.env.BUILD_ARTIFACTSTAGINGDIRECTORY ? path.join(process.env.BUILD_ARTIFACTSTAGINGDIRECTORY, `test-results/${process.platform}-${process.arch}-${args.tfs.toLowerCase().replace(/[^\w]/g, '-')}-results.xml`) : undefined
+				}
+			}),
+		);
 	} else {
 		// mocha patches symbols to use windows escape codes, but it seems like
 		// Electron mangles these in its output.
@@ -334,10 +338,13 @@ app.on('ready', () => {
 			});
 		}
 
-		applyReporter(runner, args);
+		reporters.push(applyReporter(runner, args));
 	}
 
 	if (!args.dev) {
-		ipcMain.on('all done', () => app.exit(runner.didFail ? 1 : 0));
+		ipcMain.on('all done', async () => {
+			await Promise.all(reporters.map(r => r.drain?.()));
+			app.exit(runner.didFail ? 1 : 0);
+		});
 	}
 });

test/unit/fullJsonStreamReporter.js

@@ -26,15 +26,15 @@ module.exports = class FullJsonStreamReporter extends BaseRunner {
 		super(runner, options);
 
 		const total = runner.total;
-		runner.once(EVENT_RUN_BEGIN, () => writeEvent(['start', { total }]));
-		runner.once(EVENT_RUN_END, () => writeEvent(['end', this.stats]));
+		runner.once(EVENT_RUN_BEGIN, () => this.writeEvent(['start', { total }]));
+		runner.once(EVENT_RUN_END, () => this.writeEvent(['end', this.stats]));
 
 		// custom coverage events:
-		runner.on('coverage init', (c) => writeEvent(['coverageInit', c]));
-		runner.on('coverage increment', (context, coverage) => writeEvent(['coverageIncrement', { ...context, coverage }]));
+		runner.on('coverage init', (c) => this.writeEvent(['coverageInit', c]));
+		runner.on('coverage increment', (context, coverage) => this.writeEvent(['coverageIncrement', { ...context, coverage }]));
 
-		runner.on(EVENT_TEST_BEGIN, test => writeEvent(['testStart', clean(test)]));
-		runner.on(EVENT_TEST_PASS, test => writeEvent(['pass', clean(test)]));
+		runner.on(EVENT_TEST_BEGIN, test => this.writeEvent(['testStart', clean(test)]));
+		runner.on(EVENT_TEST_PASS, test => this.writeEvent(['pass', clean(test)]));
 		runner.on(EVENT_TEST_FAIL, (test, err) => {
 			test = clean(test);
 			test.actual = err.actual;
@@ -44,14 +44,18 @@ module.exports = class FullJsonStreamReporter extends BaseRunner {
 			test.snapshotPath = err.snapshotPath;
 			test.err = err.message;
 			test.stack = err.stack || null;
-			writeEvent(['fail', test]);
+			this.writeEvent(['fail', test]);
 		});
 	}
-};
 
-function writeEvent(event) {
-	process.stdout.write(JSON.stringify(event) + '\n');
-}
+	drain() {
+		return Promise.resolve(this.lastEvent);
+	}
+
+	writeEvent(event) {
+		this.lastEvent = new Promise(r => process.stdout.write(JSON.stringify(event) + '\n', r));
+	}
+};
 
 const clean = test => ({
 	title: test.title,