test: piebiten.CopyCanvasToEbitenImage

Add basic integration tests for piebiten.CopyCanvasToEbitenImage

Author: elgopher

palettemap.go

@@ -14,7 +14,7 @@ import (
 // the contents of the Screen to the game window.
 //
 // The array index is the original color, and the value is the mapped color.
-var PaletteMapping PaletteMap = notSwappedPaletteMapping
+var PaletteMapping PaletteMap = notRemappedPalette
 
 // PaletteMap defines the color mapping for display.
 //
@@ -32,10 +32,10 @@ func (p PaletteMap) String() string {
 }
 
 func ResetPaletteMapping() {
-	PaletteMapping = notSwappedPaletteMapping
+	PaletteMapping = notRemappedPalette
 }
 
-var notSwappedPaletteMapping = func() PaletteMap {
+var notRemappedPalette = func() PaletteMap {
 	var m PaletteMap
 	for i := 0; i < MaxColors; i++ {
 		m[i] = Color(i)

piebiten/internal/ebitentesting/testing.go

@@ -0,0 +1,37 @@
+// Copyright 2025 Jacek Olszak
+// This code is licensed under MIT license (see LICENSE for details)
+
+package ebitentesting
+
+import (
+	"os"
+	"testing"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+type gameWithOneUpdate struct {
+	m    *testing.M
+	code int
+}
+
+func (g *gameWithOneUpdate) Update() error {
+	g.code = g.m.Run()
+	return ebiten.Termination
+}
+
+func (*gameWithOneUpdate) Draw(*ebiten.Image) {}
+
+func (*gameWithOneUpdate) Layout(int, int) (int, int) {
+	return 1, 1
+}
+
+// MainWithRunLoop should be Run from TestMain(*testing.M) in order to
+// run all tests inside Ebitengine's game loop
+func MainWithRunLoop(m *testing.M) {
+	g := &gameWithOneUpdate{m: m, code: 1}
+	if err := ebiten.RunGame(g); err != nil {
+		panic(err) // RunGame does not return an error for ebiten.Termination
+	}
+	os.Exit(g.code)
+}

piebiten/piebiten_test.go

@@ -0,0 +1,63 @@
+// Copyright 2025 Jacek Olszak
+// This code is licensed under MIT license (see LICENSE for details)
+
+package piebiten_test
+
+import (
+	"github.com/elgopher/pi"
+	"github.com/elgopher/pi/piebiten"
+	"github.com/elgopher/pi/piebiten/internal/ebitentesting"
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestMain(m *testing.M) {
+	ebitentesting.MainWithRunLoop(m)
+}
+
+func TestCopyCanvasToEbitenImage(t *testing.T) {
+	t.Run("should copy canvas to Ebiten image", func(t *testing.T) {
+		canvas := pi.NewCanvas(3, 2)
+		pi.Palette[0] = 0xFF0000
+		pi.Palette[1] = 0x00FF00
+		pi.Palette[2] = 0x0000FF
+		pi.Palette[3] = 0x00FFFF
+		pi.Palette[4] = 0xFFFF00
+		pi.Palette[5] = 0xFF00FF
+		canvas.SetAll(
+			0, 1, 2,
+			3, 4, 5,
+		)
+		img := ebiten.NewImage(3, 2)
+		// when
+		piebiten.CopyCanvasToEbitenImage(canvas, img)
+		// then
+		bounds := img.Bounds()
+		out := make([]byte, bounds.Dx()*bounds.Dy()*4)
+		img.ReadPixels(out)
+		for i := 0; i < 6; i++ {
+			pix := out[i*4 : i*4+4]
+			rgb := pi.FromRGB(pix[0], pix[1], pix[2])
+			assert.Equal(t, pi.Palette[i], rgb, "pixel %d", i)
+			assert.Equal(t, uint8(0xff), pix[3], "alpha for pixel %d", i)
+		}
+	})
+
+	t.Run("should take into account palette mapping", func(t *testing.T) {
+		canvas := pi.NewCanvas(1, 1)
+		pi.Palette[0] = 0x000000
+		pi.Palette[1] = 0xFFFFFF
+		pi.PaletteMapping[0] = 1 // map 0 to 1 (0x000000 to 0xFFFFFF)
+		img := ebiten.NewImage(1, 1)
+		// when
+		piebiten.CopyCanvasToEbitenImage(canvas, img)
+		// then
+		bounds := img.Bounds()
+		out := make([]byte, bounds.Dx()*bounds.Dy()*4)
+		img.ReadPixels(out)
+		pix := out[0:4]
+		rgb := pi.FromRGB(pix[0], pix[1], pix[2])
+		assert.Equal(t, pi.RGB(0xFFFFFF), rgb)
+	})
+}