Modify strategy pattern

strategy/strategy.go

@@ -1,6 +1,4 @@
-package main
-
-import "fmt"
+package strategy
 
 type Operator interface {
 	Apply(int, int) int
@@ -25,15 +23,3 @@ type Addition struct{}
 func (Addition) Apply(lval, rval int) int {
 	return lval + rval
 }
-
-func main() {
-	mult := Operation{Multiplication{}}
-
-	// Outputs 15
-	fmt.Println(mult.Operate(3, 5))
-
-	pow := Operation{Addition{}}
-
-	// Outputs 8
-	fmt.Println(pow.Operate(3, 5))
-}

strategy/strategy_test.go

@@ -0,0 +1,18 @@
+package strategy
+
+import "testing"
+
+func TestMultiplicationStrategy(t *testing.T) {
+	mult := Operation{Multiplication{}}
+
+	if res := mult.Operate(3, 5); res != 15 {
+		t.Errorf("Multiplication.Operate(3, 5) expected 15 got %q", res)
+	}
+}
+
+func TestAdditionStrategy(t *testing.T) {
+	add := Operation{Addition{}}
+	if res := add.Operate(3, 5); res != 8 {
+		t.Errorf("Addition.Operate(3, 5) expected 8 got %q", res)
+	}
+}