eng: re-add coverage support post-ESM (#227459)

Fixes #227432

test/unit/electron/renderer.js

@@ -180,7 +180,7 @@ function loadTestModules(opts) {
 /** @type Mocha.Test */
 let currentTest;
 
-function loadTests(opts) {
+async function loadTests(opts) {
 
 	//#region Unexpected Output
 
@@ -194,6 +194,8 @@ function loadTests(opts) {
 		_allowedTestOutput.push(/Deleting [0-9]+ old snapshots/);
 	}
 
+	const perTestCoverage = opts['per-test-coverage'] ? await PerTestCoverage.init() : undefined;
+
 	const _allowedTestsWithOutput = new Set([
 		'creates a snapshot', // self-testing
 		'validates a snapshot', // self-testing
@@ -283,7 +285,12 @@ function loadTests(opts) {
 			});
 		});
 
+		setup(async () => {
+			await perTestCoverage?.startTest();
+		});
+
 		teardown(async () => {
+			await perTestCoverage?.finishTest(currentTest.file, currentTest.fullTitle());
 
 			// should not have unexpected output
 			if (_testsWithUnexpectedOutput && !opts.dev) {
@@ -445,3 +452,21 @@ ipcRenderer.on('run', async (_e, opts) => {
 		ipcRenderer.send('error', err);
 	}
 });
+
+class PerTestCoverage {
+	static async init() {
+		await ipcRenderer.invoke('startCoverage');
+		return new PerTestCoverage();
+	}
+
+	async startTest() {
+		if (!this.didInit) {
+			this.didInit = true;
+			await ipcRenderer.invoke('snapshotCoverage');
+		}
+	}
+
+	async finishTest(file, fullTitle) {
+		await ipcRenderer.invoke('snapshotCoverage', { file, fullTitle });
+	}
+}