test: add test for compilation errors in watch mode

Closes #12311

Author: alan-agius4

packages/angular_devkit/build_angular/test/browser/rebuild_spec_large.ts

@@ -198,6 +198,33 @@ describe('Browser Builder rebuilds', () => {
     ).toPromise().then(done, done.fail);
   });
 
+  it('rebuilds shows error', (done) => {
+    host.replaceInFile('./src/app/app.component.ts', 'AppComponent', 'AppComponentZ');
+
+    const overrides = { watch: true, aot: false };
+    let buildCount = 1;
+    const logger = new TestLogger('rebuild-errors');
+
+    runTargetSpec(host, browserTargetSpec, overrides, DefaultTimeout * 3, logger).pipe(
+      tap((buildEvent) => {
+        switch (buildCount) {
+          case 1:
+            expect(buildEvent.success).toBe(false);
+            expect(logger.includes('AppComponent cannot be used as an entry component')).toBe(true);
+            logger.clear();
+
+            host.replaceInFile('./src/app/app.component.ts', 'AppComponentZ', 'AppComponent');
+            break;
+
+          default:
+            expect(buildEvent.success).toBe(true);
+            break;
+        }
+        buildCount ++;
+      }),
+      take(2),
+    ).toPromise().then(done, done.fail);
+  });
 
   it('rebuilds after errors in AOT', (done) => {
     // Save the original contents of `./src/app/app.component.ts`.