TestIncrease should test func increase(int, int) int in main.go

examples/module1/callbacks/main.go

@@ -1,20 +1,20 @@
 package main
 
 func main() {
-	var a *int
-	*a += 1
-	// DoOperation(1, increase)
+	DoOperation(1, increase)
 	DoOperation(1, decrease)
 }
 
 func increase(a, b int) int {
+	println("increase result is:", a+b)
 	return a + b
 }
 
-func DoOperation(y int, f func(int, int)) {
+func DoOperation(y int, f func(int, int) int) {
 	f(y, 1)
 }
 
-func decrease(a, b int) {
+func decrease(a, b int) int {
 	println("decrease result is:", a-b)
+	return a - b
 }

examples/module1/callbacks/main_test.go

@@ -6,11 +6,8 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func add(a, b int) int {
-	return a + b
-}
 func TestIncrease(t *testing.T) {
 	t.Log("Start testing")
-	result := add(1, 2)
+	result := increase(1, 2)
 	assert.Equal(t, result, 3)
 }