Mocking default instance mocks new instances

[TrueWill]

Mocking the default instance of axios (new MockAdapter(axios)) will affect any axios instances subsequently created (axios.create()).

I'm not sure that I'd call this a bug, but it's definitely surprising behavior; perhaps documenting it would be sufficient.

[donrsh]

I encountered a problem due to this recently. The situation is that I send two requests at once while mocking only the first one. I've written a wrapper function to axios request, basically call restore after response. However, the second one is also mocked, and it takes me an afternoon to find out the problem 😅

This problem is solved by ensuring that every axios request is a new instance.

[ctimmerm]

This is how axios works, I'd gladly accept a PR that adds this information to the readme.

[ReedCao]

for me, I am facing the issue opposite. I have called this (new MockAdapter(axios)) at the very beginning of my test. and inside several layers inside my codes, I called const instance = axios.create({ method: 'get', baseURL: '', timeout: 0, responseType: 'json' }) and the request is sent by this new instance. I have already mocked many APIs, however, I can't get the result as I have filled. I need do more things?

[hitao123]

i meet TypeError: Cannot read property 'defaults' of undefined