whydoesntgowork.go

whydoesntgowork.go

package main
import ("fmt")

// Real A (I cannot change this)
type RealA struct{}
func NewRealA() *RealA     { return &RealA{} }
func (a *RealA) M() string { return "real a" }

// Fake A (I can change this)
type FakeA struct{}
func NewFakeA() *FakeA     { return &FakeA{} }
func (a *FakeA) M() string { return "fake a" }

// interface for either Real or Fake A (I can change this)
type returnValue interface{ M() string }
type someFunc = func() returnValue

// fn that takes conceptually the Real A, but in tests, the Fake A (I can change this)
func greet(constructIt someFunc) string { return constructIt().M() }

// call it (I can change this)
func main() {
	fmt.Println(greet(NewRealA))
	fmt.Println(greet(NewFakeA))
}