In Go, how would I test that a mock dependency has been called in the correct way.
If I have a struct that takes a interface for a dependency, after injection I want to be able to test the original mock object has been called.
My current code in this example I can not see that the struct value has changed. If I change my code to pass by reference it triggers the error:
s.simpleInterface.Call undefined (type *SimpleInterface is pointer to interface, not interface)
type SimpleInterface interface {
Call()
}
type Simple struct {
simpleInterface SimpleInterface
}
func (s Simple) CallInterface() {
s.simpleInterface.Call()
}
type MockSimple struct {
hasBeenCalled bool
}
func (ms MockSimple) Call() {
ms.hasBeenCalled = true
}
func TestMockCalled(t *testing.T) {
ms := MockSimple{}
s := Simple{
simpleInterface: ms,
}
s.CallInterface()
if ms.hasBeenCalled != true {
t.Error("Interface has not been called")
}
}
I see three easy ways to fix this:
1- Change the signature of the Call method to receive a pointer to MockSimple, and when instantiating the Simple struct, give it the address of your mock:
func (ms *MockSimple) Call() {
ms.hasBeenCalled = true
}
func TestMockCalled(t *testing.T) {
ms := MockSimple{}
s := Simple{
simpleInterface: &ms,
}
s.CallInterface()
if ms.hasBeenCalled != true {
t.Error("Interface has not been called")
}
}
2- Not the cleanest solution, but still works. Use it if you really cant use #1. Declare "hasBeenCalled" somewhere else and change your MockSimple to hold a pointer to it:
type MockSimple struct {
hasBeenCalled *bool
}
func (ms MockSimple) Call() {
*ms.hasBeenCalled = true
}
func TestMockCalled(t *testing.T) {
hasBeenCalled := false
ms := MockSimple{&hasBeenCalled}
s := Simple{
simpleInterface: ms,
}
s.CallInterface()
if hasBeenCalled != true {
t.Error("Interface has not been called")
}
}
3- Probably a really bad solution: using globals, so I would only use it as a last resort (always avoid global state). Make "hasBeenCalled" a global and modify it from the method.
var hasBeenCalled bool
type MockSimple struct{}
func (ms MockSimple) Call() {
hasBeenCalled = true
}
func TestMockCalled(t *testing.T) {
ms := MockSimple{}
s := Simple{
simpleInterface: ms,
}
s.CallInterface()
if hasBeenCalled != true {
t.Error("Interface has not been called")
}
}
Cheers!