:sparkles: (Go) struct and interfaces

Go/shapes/shapes.go

···
+package shapes
+
+import "math"
+
+type Shape interface {
+    Area() float64
+}
+
+type Rectangle struct {
+    Width float64
+    Height float64
+}
+
+func (r Rectangle) Area() float64 {
+    return r.Width * r.Height
+}
+
+type Circle struct {
+    Radius float64
+}
+
+func (c Circle) Area() float64 {
+    return math.Pi * c.Radius * c.Radius
+}
+
+func Perimeter(rectangle Rectangle) float64 {
+    return 2 * (rectangle.Width + rectangle.Height)
+}

Go/shapes/shapes_test.go

···
+package shapes
+
+import "testing"
+
+func TestPerimeter(t *testing.T) {
+    rectangle := Rectangle{10.0, 10.0}
+    got := Perimeter(rectangle)
+    want := 40.0
+
+    if got != want {
+        t.Errorf("got %.2f want %.2f", got, want)
+    }
+}
+
+func TestArea(t *testing.T) {
+    checkArea := func(t testing.TB, shape Shape, want float64) {
+        t.Helper()
+        got := shape.Area()
+
+        if got != want {
+            t.Errorf("got %g want %g", got, want)
+        }
+    }
+
+    t.Run("rectangles", func(t *testing.T) {
+        rectangle := Rectangle{12.0, 6.0}
+        checkArea(t, rectangle, 72.0)
+    })
+
+    t.Run("circles", func(t *testing.T) {
+        circle := Circle{10.0}
+        checkArea(t, circle, 314.1592653589793)
+    })
+}