Minitest - calling a mocked instance method from within another instance method

I've come across some weird behavior in Minitest::Mock and can't figure out what's the reason behind it.

Minitest::Mock

Say I have this class A that has a method b that calls method c:

b

c

class A

def b
c
end

def c
1
end

end


I would like to mock the c method to return 2 instead of 1:

c

require 'minitest/autorun'

a = Minitest::Mock.new(A.new)
a.expect(:c, 2)


But for some reason b still returns 1:

b

> a.b
=> 1


Obviously calling c directly will work:

c

> a.c
=> 2
> a.c
MockExpectationError: No more expects available for :c:


Why is the expectation on c not being invoked when calling it from within the instance?

c

1 Answer
1

This is how Minitest::Mock works; the mock object is a wrapper around the "real" instance of A, and defined expectations intercept the method call before it ever gets to that instance. (Other methods, like b, with no expectations defined, are forwarded on unaffected -- though they do still pass through the mock.)

Minitest::Mock

A

b

When the instance makes method calls internally, they go directly to self, not back through the mock wrapper, so they're dispatched normally, with no chance for interception.

self

c

#save

#save

stub

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