test(attach): fix "emits disconnect" timeout #414

Problem:
This test may time out, because the `proc.on('close')` event is never triggered.

    FAIL src/attach/attach.test.ts (5.62 s)
      ● Nvim API › emits "disconnect" after quit
        thrown: "Exceeded timeout of 5000 ms for a test while waiting for `done()` to be called.

          |   });
          |
        > |   it('emits "disconnect" after quit', done => {
          |   ^
          |     const disconnectMock = jest.fn();
          |     nvim.on('disconnect', disconnectMock);
          |     nvim.quit();

          at it (src/attach/attach.test.ts:138:3)
          at Object.describe (src/attach/attach.test.ts:6:1)

Solution:
Listen for 'exit' instead of 'close'. This may indicate that Nvim or node-client
is not properly closing all of its streams, but that is unrelated to this
particular test.

Author: gjf7

packages/neovim/src/attach/attach.test.ts

@@ -157,10 +157,12 @@ describe('Nvim API', () => {
   it('emits "disconnect" after quit', done => {
     const disconnectMock = jest.fn();
     nvim.on('disconnect', disconnectMock);
+
     nvim.quit();
 
-    proc.on('close', () => {
-      expect(disconnectMock.mock.calls.length).toBe(1);
+    // TODO: 'close' event sometimes does not emit. #414
+    proc.on('exit', () => {
+      expect(disconnectMock).toHaveBeenCalledTimes(1);
       done();
     });