Effective testing for IPC events?

I'm trying to find a way of effectively testing for IPC events being sent/received on either the main or renderer processes.

Looking at the spectron tests, I came across this: https://github.com/electron/spectron/blob/master/test/application-test.js#L219. However, this approach of assigning a global variable within the main process seems awkward. It also requires modifying the application's code just to enable the test capability for any given IPC event.

I tried the following to no avail:

it("listens for a message on ipcRenderer", function(done) {
    app.client.waitUntilWindowLoaded().then(() => {
      const ipcRenderer = app.electron.ipcRenderer;

      ipcRenderer.on('msg-received', function(evt, payload) {
        payload.should.be("SUCCESS")
        done()
      })

      ipcRenderer.send("msg-received", "SUCCESS")
    })
  });

Evens sent directly from within the renderer process also won't be captured by tests, and I suspect it's because mocha's test process is separate from the process running Electron.

So, is it possible to receive Electron events from either process within a Spectron test, in a similar manner to the example above? I suspect not, but if this is the case, what can be done to enable this capability?

Start with Spectron's referenced test/application-test.js#L219 and the ipcRenderer test example in this issue. Trace how the test process communicates with the main and renderer processes, then check whether an existing Spectron entry point supports IPC observation without application changes. Done means a supported approach is identified or the limitation and required capability are documented.