Golang: Replace function unit testing

I'm working with Golang, and currently I'm doing some fun unit test with Testify, my file look like this

type myStruct struct {
  field_1 string
}
func (self *myStruct) writeFirst()  {
//doing something
//modify field_1
self.writeSecond()
}
func (self *myStruct) writeSecond() {
//doing something
}

In this case I'm testing writeFirst() but I'm trying to replace writeSecond() because it is using http stuff that I don't want to use because it access to internet.

I think that use a second struct and set myStruct as anonymous field will be the solution, but it's not working because me second struct and myStruct have a diferent context.

In this case I can't use mocks cause writeSecond is a method of the struct.

My test case looks like this:

func TestWriteFirst(t *testing.T) {
   myStc := myStruct{}
   assert.Equal(t,"My response", myStc.field_1)
}

All that I want is testing writeFirst without pass to writeSecond()

To illustrate the kind of refactoring mentioned by Not-a-Golfer in the comments, you could consider calling your second function only on an instance that is an interface:

type F2er interface {
	Func2()
}
type S struct{ _f2 F2er }
var s = &S{}
func (s *S) f2() F2er {
	if s._f2 == nil {
		return s
	}
	return s._f2
}
func (s *S) Func1() {
	fmt.Println("s.Func1")
	s.f2().Func2()
}

Here: Func1 calls Func2 on s.f2(), not directly s.

• If nothing has been set in s, s.f2() returns... itself: s
• if s._f2 was replaced by any other struct which implements Func2, s.f2() returns that instance instead of itself.

See a complete example in this playground script.

Output:

TestFunc1
s.Func1
s.Func2
TestFunc1bis
s.Func1
testS.Func2    <=== different Func2 call