test: add poll test

tests/e2e/tests/build/poll.ts

@@ -0,0 +1,27 @@
+import {
+  killAllProcesses,
+  waitForAnyProcessOutputToMatch,
+  silentExecAndWaitForOutputToMatch
+} from '../../utils/process';
+import {appendToFile} from '../../utils/fs';
+import {expectToFail, wait} from '../../utils/utils';
+
+const webpackGoodRegEx = /webpack: Compiled successfully./;
+
+export default function() {
+  return silentExecAndWaitForOutputToMatch('ng', ['serve', '--poll=10000'], webpackGoodRegEx)
+    // Wait before editing a file.
+    // Editing too soon seems to trigger a rebuild and throw polling out of whack.
+    .then(() => wait(2000))
+    .then(() => appendToFile('src/main.ts', 'console.log(1);'))
+    .then(() => waitForAnyProcessOutputToMatch(webpackGoodRegEx, 12000))
+    .then(() => appendToFile('src/main.ts', 'console.log(1);'))
+    // No rebuilds should occur for a while
+    .then(() => expectToFail(() => waitForAnyProcessOutputToMatch(webpackGoodRegEx, 6000)))
+    // But a rebuild should happen roughly within the 10 second window.
+    .then(() => waitForAnyProcessOutputToMatch(webpackGoodRegEx, 12000))
+    .then(() => killAllProcesses(), (err: any) => {
+      killAllProcesses();
+      throw err;
+    });
+}