Refactored Event Queue

[npathai]

1. Test cases were not stopping AudioService before ending test case, but test comments suggested differently.

// test that service is finished
 assertFalse(!audio.isServiceRunning()); // which is equivalent to service is running

2. Changed Audio to be a good singleton, previously because of Audio being bad singleton, test cases which were using static methods could have caused intermittent failures. After changes now each test case has dedicated instance of Audio service which provides isolation between test cases.

3. Made stop() method blocking till service stops

4. Made some other refactorings as well

Todo

• Update class diagram once PR is approved.

[IAmPramod]

1. Changed Audio to be a good singleton, previously because of Audio being bad singleton, test cases which were using static methods could have caused intermittent failures. After changes now each test case has dedicated instance of Audio service which provides isolation between test cases.

Why we are calling it as a bad singleton. It was thread-safe previously.

[npathai]

1. Changed Audio to be a good singleton, previously because of Audio being bad singleton, test cases which were using static methods could have caused intermittent failures. After changes now each test case has dedicated instance of Audio service which provides isolation between test cases.

Why we are calling it as a bad singleton. It was thread-safe previously.

@IAmPramod Bad singleton because it polluted global state. It created unseen dependency between test cases and behavior would vary on how threads get interleaved. Hence the bad.

[iluwatar]

Looks good to me

[npathai]

@iluwatar Updated the class diagram. Ready to merge!