Include imports in generated test files

[AlfieJones]

Description

This pr fixes an issue here: #136

When running tests which are in JSON mode, the test runner generates the test files for them. Under certain circumstances, these tests fail and are attempted to be restarted. From the error snippet below, we see that setupPage isn't imported into these files, this can be verified by checking the generated files code.

  ● Modules / Components / AuthDetails › App Without Auth › test

    ReferenceError: setupPage is not defined

      90 |         if (err.toString().includes('Execution context was destroyed')) {
      91 |           await jestPlaywright.resetPage();
    > 92 |           await setupPage(global.page);
         |           ^
      93 |           await testFn();
      94 |         } else {
      95 |           throw err;

      at Object.<anonymous> (../../../../../../private/var/folders/l_/7fz4zgds1cd9tkqc36p0lk0w0000gn/T/47e5eedc4767b37c9cdb92bc7c1c08b6/modules-components-authdetails.test.js:92:11)

Impact of the issue

This issue is currently causing our pipeline to be very flaky. The problem seems to be occurring once every 4 runs and I can only assume it'll get worse as we increase our storybook count. We currently have about 30.

Fix

I've just added the existing filePrefixer to the generated codes. This contains the required imports and solves the issue. I have also updated the tests accordingly.

Testing and Impact

I have built and tested a build generated from this branch on our pipeline. These changes only affect other Json mode stories ( in theory)

[yannbf]

Hey @AlfieJones thank you so much for providing a PR for this. Unfortunately, I believe this will not fix the issue.
Therefore, I created another PR at #217 to fix that issue.