test: Add unit tests for pisnap package

CaptureOrErr works only on non js OS.

Author: elgopher

pisnap/pisnap.go

@@ -7,12 +7,13 @@ package pisnap
 import (
 	"errors"
 	"fmt"
-	"github.com/elgopher/pi"
 	"image"
 	"image/color"
 	"image/png"
 	"os"
 	"runtime"
+
+	"github.com/elgopher/pi"
 )
 
 // CaptureOrErr captures a screenshot and saves it to the temporary directory.

pisnap/pisnap_js_test.go

@@ -0,0 +1,20 @@
+// Copyright 2025 Jacek Olszak
+// This code is licensed under MIT license (see LICENSE for details)
+
+//go:build js
+
+package pisnap_test
+
+import (
+	"testing"
+
+	"github.com/elgopher/pi/pisnap"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCaptureOrErr(t *testing.T) {
+	file, err := pisnap.CaptureOrErr()
+	assert.Error(t, err)
+	assert.Empty(t, file)
+}

pisnap/pisnap_nonjs_test.go

@@ -0,0 +1,37 @@
+// Copyright 2025 Jacek Olszak
+// This code is licensed under MIT license (see LICENSE for details)
+
+//go:build !js
+
+package pisnap_test
+
+import (
+	"bytes"
+	"image"
+	"image/png"
+	"os"
+	"testing"
+
+	"github.com/elgopher/pi"
+	"github.com/elgopher/pi/pisnap"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCaptureOrErr(t *testing.T) {
+	// when
+	file, err := pisnap.CaptureOrErr()
+	// then
+	require.NoError(t, err)
+	assert.NotEmpty(t, file)
+	// and file exists
+	f, err := os.ReadFile(file)
+	require.NoError(t, err, "cannot read PNG file")
+	// and
+	img, err := png.Decode(bytes.NewReader(f))
+	require.NoError(t, err, "file is not a valid PNG")
+	// and
+	palettedImage, ok := img.(*image.Paletted)
+	require.True(t, ok, "image is not a Paletted")
+	assertPalettedImage(t, palettedImage, pi.Screen())
+}

pisnap/pisnap_test.go

@@ -0,0 +1,60 @@
+// Copyright 2025 Jacek Olszak
+// This code is licensed under MIT license (see LICENSE for details)
+
+package pisnap_test
+
+import (
+	"image"
+	"testing"
+
+	"github.com/elgopher/pi"
+	"github.com/elgopher/pi/pisnap"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPalettedImage(t *testing.T) {
+	pi.SetScreenSize(2, 3)
+	pi.Palette[1] = 0xffaa44
+	pi.Palette[2] = 0xff0000
+	pi.Palette[3] = 0x00ff00
+	pi.Palette[4] = 0x0000ff
+	pi.Palette[5] = 0x00ffff
+	pi.Palette[6] = 0xff00ff
+	screen := pi.Screen()
+	screen.SetAll(1, 2, 3, 4, 5, 6)
+	// when
+	img := pisnap.PalettedImage()
+	// then
+	assertPalettedImage(t, img, screen)
+}
+
+func assertPalettedImage(t *testing.T, img image.PalettedImage, screen pi.Canvas) {
+	t.Helper()
+
+	// then color indexes are the same
+	for y := 0; y < screen.H(); y++ {
+		for x := 0; x < screen.W(); x++ {
+			actual := img.ColorIndexAt(x, y)
+			expected := screen.Get(x, y)
+			assert.Equal(t, expected, actual)
+		}
+	}
+	// and RGBA colors match
+	for y := 0; y < screen.H(); y++ {
+		for x := 0; x < screen.W(); x++ {
+			r, g, b, a := img.At(x, y).RGBA()
+			assert.Equal(t, uint8(0xff), uint8(a))
+			actual := pi.FromRGB(uint8(r), uint8(g), uint8(b))
+			expected := pi.Palette[screen.Get(x, y)]
+			assert.Equal(t, expected, actual)
+		}
+	}
+	// and size is the same
+	assert.Equal(t,
+		image.Rectangle{
+			Max: image.Point{X: screen.W(), Y: screen.H()},
+		},
+		img.Bounds(),
+		"image size is not same as screen size",
+	)
+}