Commit b77aa05

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+go test -v

@@ -1,14 +0,0 @@
-package main
-
-type Rectangle struct {
-	Width  float64
-	Height float64
-}
-
-func Perimeter(rectangle Rectangle) float64 {
-	return 2 * (rectangle.Width + rectangle.Height)
-}
-
-func Area(rectangle Rectangle) float64 {
-	return rectangle.Width * rectangle.Height
-}

@@ -1,25 +0,0 @@
-package main
-
-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) {
-	rectangle := Rectangle{12.0, 6.0}
-	got := Area(rectangle)
-	want := 72.0
-
-	if got != want {
-		t.Errorf("got %.2f want %.2f", got, want)
-	}
-}

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"math"
+)
+
+func Perimeter(rectangle Rectangle) float64 {
+	return 2 * (rectangle.Width + rectangle.Height)
+}
+
+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
+}

@@ -0,0 +1,35 @@
+package main
+
+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) {
+	tests := []struct {
+		name  string
+		shape Shape
+		want  float64
+	}{
+		{"rectangles", Rectangle{12, 6}, 72.0},
+		{"circles", Circle{10}, 314.1592653589793},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got := test.shape.Area()
+			if got != test.want {
+				t.Errorf("got %g want %g", got, test.want)
+			}
+		})
+	}
+}