add testcase for util

.github/workflows/go.yml

@@ -22,4 +22,4 @@ jobs:
       run: go build -v ./*.go
 
     - name: Test
-      run: go test -v ./...
+      run: go test -v ./*.go

utils_test.go

@@ -0,0 +1,31 @@
+package generativeart
+
+import (
+	"math"
+	"testing"
+)
+
+func TestDistance(t *testing.T) {
+	type args struct {
+		x1 float64
+		y1 float64
+		x2 float64
+		y2 float64
+	}
+	tests := []struct {
+		name string
+		args args
+		want float64
+	}{
+		{name: "testcase1", args: args{x1:0, y1:0, x2:0, y2:0}, want: 0},
+		{name: "testcase2", args: args{x1:0, y1:3, x2:4, y2:0}, want: 5},
+		{name: "testcase3", args: args{x1:1, y1:1, x2:0, y2:0}, want: 1.414213562},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := Distance(tt.args.x1, tt.args.y1, tt.args.x2, tt.args.y2); math.Abs(got-tt.want)>0.00001 {
+				t.Errorf("Distance() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}