Allow mocking methods updating referenced structs

[ernesto-jimenez]

Some methods in Go take a pointer to a struct or a map and are supposed to set some values in the referenced argument. Using Return is not enough to mock such methods.

We are introducing a Run method that allows setting a Call handler to make your mock update such referenced values.

Example usage mocking a service that finds a user in a data store and fills the values in the provided struct:

m.On("Find", 1, mock.AnythingOfType("*User"))
  .Return(nil)
  .Run(func(args mock.Arguments) {
  u := args.Get(0).(*User)
  u.ID = 1
  u.Email = "[email protected]"
})

[ernesto-jimenez]

@DAddYE, do you mind reviewing this?

Ideally it would be m.On(...).Run(...).Return(...), but it cannot be done right now due to the package internals, so we had to settle for doing m.On(...).Return(...).Run(...)

Thanks!

/cc @rnaveiras

[DAddYE]

Looks good to me! 👍

[ernesto-jimenez]

Merged, thanks!