How I Fixed: TypeError: Invalid attempt to destructure non-iterable instance

This morning I hit upon a really annoying problem whilst trying to write a basic test for a React component.

The internals of the component are not important to the issue I was facing.

Here’s the outcome:

What frustrated me was that the first it block was working. And then the second block would not work.

I could xit the first it, and then the second it would work / pass. But together, they would not play nicely.

The reason for this is something that’s caught me out several times previously, but something I keep forgetting about. Here we go:

The issue is the use of jest.resetAllMocks();.

Here’s what it should be:

In case you missed it, switch resetAllMocks for clearAllMocks.

The reasoning, in my case is that I had declared a .mockImplementation elsewhere in my test, and a call to resetAllMocks wipes out that mock implementation.

At least, that’s my understanding of it.

For more details see the docs for the difference between resetAllMocks and clearAllMocks.