lambda-tester | Helper for unit testing AWS Lambda functions | Runtime Evironment library

Your problem is not whether Sinon supports this or that, but rather a missing understanding of how "classes" work in Ecmascript, as shown by the attempt at stubbing constructor property in the test code. That will never work, as that property has nothing to do with how any resulting objects turn out. It is simply a reference to the function that was used to create the object. I have covered a very similar topic on the Sinon tracker that you might have interest in reading to gain some core JS foo :-) Basically, it is not possible to stub a constructor, but you can probably coerce your code to use another constructor function in its place through either DI or link seams.

As a matter of fact, a few answers down in the same thread, you will see me covering an example of how I myself designed a Redis using class to be easily testable by supporting dependency injection. You might want to check it out, as it is more or less directly applicable to your example module above.

Another technique, which you already has tried getting to work, is using link seams (using rewire). The Sinon homepage has a nice article on doing this. Both rewire and proxyquire will do the job just fine here: I think you have just complicated the matter a bit by wrapping the require statement with a mock.

Even though I am on the Sinon maintainer team, I never use the mock functionality, so I cannot tell you how to use that, as I think it obscures the testing, but to get the basic link seams working using rewire I would basically remove all the Sinon code first and get the basic case going (removing redis for a stubbed module you have created).

Only then, add Sinon code as required.

You could do something along the lines of:

Use lamba-tester, there are examples on the github page.

I wrote a simple lambda test function and then tested the output with jasmine + lambda-tester

As for my code, I'll need to refactor the handler someone else wrote before it will work. My simple test looks like:

Serverless yml

There seems to be nothing wrong with your code.

One of the biggest difference between mocha and jest is that jest runs tests concurrently and therefore it can detect issues like race conditions and mutations outside your handler on your Lambda that mocha may miss.

Here's I would troubleshoot it:

• Try to run that single test multiple times (that single file and that single test using test.only).
• Try running the entire suite serially using jest --runInBand.

If we get consistent failures with those, then you probably have race condition issues and/or maybe a bug in your code where you store state outside of your handler and it is being shared by different invocations.