proposal: change order expectations are evaluated

[poy]

Add option to NewController() (see #238 ) to enable reversing the evaluation order.

Proposal

gmock applies expectations in reverse order. This allows the following pattern:

// sut.go
type A interface {
  Foo(i int) int
}

type Something struct{
  a A
}

func NewSomething(a A) *Something {
  return Something{}
}

func (s *Something) Do(i int) {
  s.a.Foo(i)
}

// sut_test.go
func beforeEach(t *testing.T) A {
  ctrl := gomock.NewController(t)
  mockA := NewMockA()

  // Stub - Always returns 99
  mockA.
    EXPECT().
    Foo(gomock.Any()).
    Return(99).
    AnyTimes()
}

func TestFoo_OnlyDefault(t *testing.T){
  mockA := beforeEach(t)
  
  s := NewSUT(mockA)
  s.Do(5) // Mock doesn't make any assertion on value
}

func TestFoo_WithAssertion(t *testing.T){
  mockA := beforeEach(t)
  
  mockA.
    EXPECT().
    Foo(101).
    Return(99)

  s := NewSUT(mockA)
  s.Do(5) // Latest assertion will fail
}

This pattern will currently fail as the first assertion is evaluated first, as it is an AnyTimes(), it will always be successful and therefore the last assertion (the one we really care about for TestFoo_WithAssertion) won't be applied.

[poy]

Related to #137 #188 #7

[tocrafty]

Agreed. This would be very usefull to inject faults to mocked objects.