Added a sanity test for Bridge shutdown

src/__tests__/bridge-test.js

@@ -0,0 +1,42 @@
+// @flow
+
+describe('Bridge', () => {
+  let Bridge;
+
+  beforeEach(() => {
+    Bridge = require('src/bridge').default;
+  });
+
+  it('should shutdown properly', () => {
+    const wall = {
+      listen: jest.fn(() => () => {}),
+      send: jest.fn(),
+    };
+    const bridge = new Bridge(wall);
+
+    // Check that we're wired up correctly.
+    bridge.send('init');
+    jest.runAllTimers();
+    expect(wall.send).toHaveBeenCalledWith('init', undefined, undefined);
+
+    // Should flush pending messages and then shut down.
+    wall.send.mockClear();
+    bridge.send('update', '1');
+    bridge.send('update', '2');
+    bridge.shutdown();
+    jest.runAllTimers();
+    expect(wall.send).toHaveBeenCalledWith('update', '1', undefined);
+    expect(wall.send).toHaveBeenCalledWith('update', '2', undefined);
+    expect(wall.send).toHaveBeenCalledWith('shutdown', undefined, undefined);
+
+    // Verify that the Bridge doesn't send messages after shutdown.
+    spyOn(console, 'warn');
+    wall.send.mockClear();
+    bridge.send('should not send');
+    jest.runAllTimers();
+    expect(wall.send).not.toHaveBeenCalled();
+    expect(console.warn).toHaveBeenCalledWith(
+      'Cannot send message "should not send" through a Bridge that has been shutdown.'
+    );
+  });
+});