Demo for Dependency Injection with Golang

after_di.go

package di

import (
	"fmt"
)

func AverageScore() float64 {
	score := getTotalScore()
	member := getAllMember()
	return float64(score / member)
}

var getAllMember = func() int {
	return 10
}

var getTotalScore = func() int {
	return 100
}

func main() {
	fmt.Println(AverageScore())
}

before_di.go

package di

import (
     "fmt"
)

func AverageScore() float64 {
     score := getTotalScore()
     member := getAllMember()
     return float64(score/member)
}

func getAllMember() int {
     return 10
}

func getTotalScore() int {
     return 100
}

func main() {
     fmt.Println( AverageScore() )
}

test_mock.go

func TestAverageScoreMock(t *testing.T) {
	var callTotalScore = 0
	var callAllMember = 0

	getTotalScore = func() int {
		callTotalScore++;
		return 50
	}
	getAllMember = func() int {
		callAllMember++;
		return 2
	}

	AverageScore()
	if callTotalScore != 1 { t.Error("getTotalScore should have been called 1 time only") }
	if callAllMember != 1 { t.Error("getAllMember should have been called 1 time only") }
}

test_real.go

func TestAverageScoreReal(t *testing.T) {
	var result = AverageScore()
	if result != 10 {
		t.Errorf("Expected %v to equal average", 10)
	}
}

test_stub.go

func TestAverageScoreStub(t *testing.T) {
	getTotalScore = func() int {
		return 200
	}
	getAllMember = func() int {
		return 5
	}

	var result = AverageScore()
	if result != 40 {
		t.Errorf("Expected %v to equal average", 40)
	}
}