Modify strategy pattern

strategy/strategy.go

@@ -0,0 +1,25 @@
+package strategy
+
+type Operator interface {
+	Apply(int, int) int
+}
+
+type Operation struct {
+	Operator Operator
+}
+
+func (o *Operation) Operate(leftValue, rightValue int) int {
+	return o.Operator.Apply(leftValue, rightValue)
+}
+
+type Multiplication struct{}
+
+func (Multiplication) Apply(lval, rval int) int {
+	return lval * rval
+}
+
+type Addition struct{}
+
+func (Addition) Apply(lval, rval int) int {
+	return lval + rval
+}

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)
+	}
+}