Jest tests are not running after updating from 5.0.* to 5.1.7

[petercmuc]

We recently updated the „merge-anything“ dependency in our project from 5.0.2 to version 5.1.7 which changes how the exported files are treated. This is a breaking change...
The default export is now modules instead of commonjs (https://github.com/mesqueeb/merge-anything/blob/v5.1.7/package.json#L9). Unfortunately, Jest in combination with stencil does not support modules in test so far (ionic-team/stencil#3230). These two things together simply break the tests with a more or less helpful messages.

[danielcrisp]

@petercmuc I was able to workaround this by making Jest transform the module (via Babel). You can do that with transformIgnorePatterns

https://jestjs.io/docs/configuration#transformignorepatterns-arraystring

For example:

import type { Config } from 'jest';

const config: Config = {
  transformIgnorePatterns: [
    '/node_modules/(?!merge-anything|is-what)'
  ],
};

export default config;

(I had to include is-what too as it is used by merge-anything)