Run wilde on iOS emulator during electron tests

Summary:
Before running the test suite, build wilde and run it on a local emulator.

This takes about 15 mins on a lego-mac with a warm cache.
It's probably worth splitting out the normal unit tests into a separate job, so we get quicker feedback on them. I'll do that in a separate diff.

Lets run this for a while, and see how it goes, I'm wondering if it might get flaky because it will be building the master version of wilde, so potentially could be broken a lot, though it's passed evry time I've tried it so far.

If it's reliable, we can run the same thing with loads of other apps in parallel.

Reviewed By: passy

Differential Revision: D10110408

fbshipit-source-id: 61c549eb1b9d04729dcb5ed01271a484af4777f5

src/__tests__/server.electron.js

@@ -26,18 +26,31 @@ beforeAll(() => {
 test('servers starting at ports', done => {
   const serversToBeStarted = new Set([SECURE_PORT, INSECURE_PORT]);
 
-  server.addListener('listening', port => {
-    if (!serversToBeStarted.has(port)) {
-      done.fail(Error(`unknown server started at port ${port}`));
-    } else {
-      serversToBeStarted.delete(port);
-    }
-    if (serversToBeStarted.size === 0) {
-      done();
-    }
+  return new Promise((resolve, reject) => {
+    server.addListener('listening', port => {
+      if (!serversToBeStarted.has(port)) {
+        throw Error(`unknown server started at port ${port}`);
+      } else {
+        serversToBeStarted.delete(port);
+      }
+      if (serversToBeStarted.size === 0) {
+        done();
+        resolve();
+      }
+    });
   });
 });
 
+test(
+  'Layout plugin is connecting',
+  done => {
+    server.addListener('new-client', (client: Client) => {
+      done();
+    });
+  },
+  10000,
+);
+
 afterAll(() => {
   server.close();
 });