Why esm module not imported on the test by jest

I have a UI framework that is maintained by my company. and This library doesn't provide cjm module. instead only provide esm module.

And I aware that this library is not failed to be imported from the test condition running by jest.

through some gogooling, I found that the Jest doesn't support ESM module import, and it is only on experimental stage to support esm module on Jest(https://jestjs.io/docs/ecmascript-modules). So I tried to make my library as cjs module version, and test againg. This is perfectly works. So I convinced that the previous bug was caused because Jest doesn't support esm module import.

But at this point, I wonder something below.

1. If Jest don't support ESM, every library should have cjs module regardless of providing esm module??

2. Jest always find only cjs module from libraries?

3. How React test works on jest? even thought every react component and other modules are ESM? This is why we need react-test-renderer or babel-jest as dependencies for the react test?

4. Finally, There is some resources that I can find some information about this subject??