Mocha Runcycle and flow of execution

Parallel Mode

1. Skip reporter validation and repeat steps 1 through 5 from Serial Mode.
2. All test files discovered are added to a queue (they are not loaded by the main process)
3. If there are any global setup fixtures, Mocha will run them.
4. Mocha produces a "worker" pool of subprocesses.
5. A worker "bootstraps" itself immediately before running the first test it gets by:
   1. All --require'd modules are being loaded.
   2. Plugins for root hooks must be registered.
   3. Ignoring international conventions and custom reports
   4. Asserting the validity of a built-in or custom interface
6. When a worker receives a test file to run, it starts a new Mocha instance for the single test file, and then:
7. Step 7 is repeated by the worker.
8. The worker replicates step 10 above, with the exception that it does not directly submit test findings; instead, it stores them in a memory buffer.
9. When the worker finishes the test file, the results are buffered and returned to the main process, which then sends them to the reporter designated by the user (spec by default)
10. If there are any remaining test files, the worker makes himself available to the pool; the pool provides the worker another test file to run.
11. If necessary, Mocha prints a final summary/epilog.
12. If there are any global teardown fixtures, Mocha will run them.

FAQs

1. How does Mocha Testing work?
   Mocha is a powerful JavaScript test framework that runs on Node.js and in the browser, making asynchronous testing easy and enjoyable. Mocha tests run in a sequential order, allowing for flexible and precise reporting while mapping uncaught exceptions to the appropriate test cases.
    
2. Does Mocha execute tests in order?
   Mocha will run the tests in the order the describe calls execute.
    
3. Does Mocha run tests in parallel?
   Individual tests are not executed in parallel by Mocha. That is, if you provide Mocha a solitary, lonely test file, it will create a single worker process, which will run the file. You'll be punished for using parallel mode if you just have one test file.
    
4. What is done() in Mocha?
   This "done" option tells Mocha that you're writing an asynchronous test when it's included in your callback method.

Key Takeaways

In this blog, we discussed in detail the way tests are executed in Mocha.js. We discussed the workflow in serial and parallel modes and also came up with interesting questions in the FAQs section. We saw that in the parallel mode of execution, some of the steps are the same as that in serial mode.

You can follow this interesting article from Coding Ninjas to get started with Mocha.js.

We hope that this blog has helped you enhance your knowledge regarding Flow of execution and runcycle in Mocha.js and if you would like to learn more, head over to our practice platform Coding Ninjas Studio to practice top problems, attempt mock tests, read interview experiences, and much more.! Do upvote our blog to help other ninjas grow. 
Happy Coding!.