Added support for getting the arguments of mock function call for a specific call count

Summary

The purpose of this change is to enable asserting the arguments of a mock function for a specific call count.

Changes

Updated the Mock struct to hold the map of methodName to a slice of calls instead of just a slice of Calls, this will be used to extract the calls for a given methodName easily

Motivation

For instance, when a method is invoked multiple times within the code, and there's a need to verify the arguments for a particular call count, this enhancement proves beneficial.

actualObject.ProcessData("data1")
actualObject.ProcessData("data2")

with the new API, can assert the argument for a second call like this .

returnArgs := mockedObject.ArgsForCallCount(t, "ProcessData", 1)
if assert.Equal(t, 1, len(returnArgs)) {
     assert.Equal(t, "data2", returnArgs[0])            
}

Related issues

N/a

stretchr / testify