Resolve Performance test failures and add unit tests for proto3 data transport format

[zijianjoy]

1. Add a timeout wait function to cc_service.test.ts because the first setTimeout() happens before fake timer is used. (Resolve test failure from Travis CI)
2. Remove .only() from cc_service.test.ts file so other Fireperf test can be run.
3. Add unit tests to validate proto3 format serialization works as expected.

[hsubox76]

So I tried this out and I don't think any of these 3 tests actually run, as written. When a test is async you have to handle it with a done() or by returning a promise, or else Mocha will just go on to the next test and not wait for the async part to finish, and count it as passed. I think as the code currently stands, you can put anything in the callback and it will pass.

If you wanted it to reach the expect line you'd want

    it('throws an error when logging an empty message', (done) => {
      waitForFirstTimeout(() => {
        const logger = new Logger('@firebase/performance/cc');
        expect(() => {
          testCCHandler(logger, LogLevel.SILENT, '');
        }).to.throw;
       done();
      });
    });

Or instead of using done(), return a promise.

I'm able to get around the described problem (doing a real time offset before tests begin, which allows all imported instances of ccHandler to reach the initial setTimeout callback of processQueue) with this block, which runs before all tests.

before((done) => {
      setTimeout(() => done(), INITIAL_SEND_TIME_DELAY_MS);
    });

You don't need to run this before each test, just all tests, because all instances of the top level call to processQueue runs before any tests which I don't think is what you expect or want, so, can I suggest not calling processQueue automatically at the top level of cc_service.ts but instead providing an init function to run it, which perf_logger.ts can call at the top. This way each test can call the init on its own time and not have to do any kind of setTimeout workaround.

Also another warning, if this code worked as intended (using done() or a promise return to pause the async test until timeout ends and the expect runs), the waitForFirstTimeout would wait on the real time clock, and I think it's set to 100 seconds (10 * 10 * 1000) and on the real time clock that would be bad.

[zijianjoy]

Thank you Christina for the detailed feedback and tried with the testing! I have updated the logic in cc_service.ts to provide an init function and updated tests to include fake timer inside describe(). Since this test update is separated from feature branch merge in this PR (fireperf-update-log-format), I created master branch PR for this #2506. Thank you!