Mock Builtin 'open" Function When Used In Contextlib

I know this question has been asked before, but I have a particular problem, meaning I want the mock_open to actually return a specific mock object. I have a function I want to tes

Solution 1:

What do you want is that mocked open return a different mock object for the two calls: you can use side_effect to obtain that behavior but you need a little trick to create valid mocked file handler

m = msrc = mock_open() #That create a handle for the first file
mdst = mock_open() #That create a handle for the second file
m.side_effect=[msrc.return_value,mdst.return_value] # Mix the two handles in one of mock the we will use to patch openwith patch("builtins.open", m):
    withopen("src",'r') as src , open("dest",'w') as dest:
        print(src)   #Two different mock file!print(dest)

I wrote the code for python 3 but should be simple translate it for older python (I noted that you use nested).

I already give an answer to a very similar issue but that solution is much better! Just for the record Python mock builtin 'open' in a class using two different files