test(core): add video buffer and palette tests

tests/Chip8.Tests/VideoTests.cs

@@ -0,0 +1,107 @@
+using Chip8.Core;
+using Xunit;
+
+namespace Chip8.Tests;
+
+public class VideoTests
+{
+    static Video withPixel(int x, int y, int planeMask = 1)
+    {
+        var video = new Video();
+        var sprite = new byte[] { 0x80 };
+        video.drawSprite(sprite, 0, x, y, 1, planeMask, false);
+        return video;
+    }
+
+    [Fact]
+    public void scrollDownMovesRowsDown()
+    {
+        var video = withPixel(5, 2);
+        video.scrollDown(3, 1);
+        Assert.False(video.pixel(0, 5, 2));
+        Assert.True(video.pixel(0, 5, 5));
+    }
+
+    [Fact]
+    public void scrollUpMovesRowsUp()
+    {
+        var video = withPixel(5, 10);
+        video.scrollUp(3, 1);
+        Assert.False(video.pixel(0, 5, 10));
+        Assert.True(video.pixel(0, 5, 7));
+    }
+
+    [Fact]
+    public void scrollRightMovesColumnsRight()
+    {
+        var video = withPixel(5, 2);
+        video.scrollRight(4, 1);
+        Assert.False(video.pixel(0, 5, 2));
+        Assert.True(video.pixel(0, 9, 2));
+    }
+
+    [Fact]
+    public void scrollLeftMovesColumnsLeft()
+    {
+        var video = withPixel(9, 2);
+        video.scrollLeft(4, 1);
+        Assert.False(video.pixel(0, 9, 2));
+        Assert.True(video.pixel(0, 5, 2));
+    }
+
+    [Fact]
+    public void scrollRespectsPlaneMask()
+    {
+        var video = new Video();
+        var sprite = new byte[] { 0x80 };
+        video.drawSprite(sprite, 0, 5, 2, 1, 0x3, false);
+        video.scrollDown(3, 0x1);
+        Assert.True(video.pixel(0, 5, 5));
+        Assert.True(video.pixel(1, 5, 2));
+        Assert.False(video.pixel(1, 5, 5));
+    }
+
+    [Fact]
+    public void setResolutionHiresResizesAndClears()
+    {
+        var video = withPixel(5, 2);
+        video.setResolution(true);
+        Assert.Equal(Video.hiWidth, video.width);
+        Assert.Equal(Video.hiHeight, video.height);
+        Assert.False(video.pixel(0, 5, 2));
+    }
+
+    [Fact]
+    public void drawSpriteWrapsAroundEdgesWhenNotClipping()
+    {
+        var video = new Video();
+        var sprite = new byte[] { 0xC0 };
+        video.drawSprite(sprite, 0, 63, 0, 1, 1, true);
+        Assert.True(video.pixel(0, 63, 0));
+        Assert.True(video.pixel(0, 0, 0));
+    }
+
+    [Fact]
+    public void drawSpriteClipsAtEdgeWhenClipping()
+    {
+        var video = new Video();
+        var sprite = new byte[] { 0xC0 };
+        video.drawSprite(sprite, 0, 63, 0, 1, 1, false);
+        Assert.True(video.pixel(0, 63, 0));
+        Assert.False(video.pixel(0, 0, 0));
+    }
+
+    [Fact]
+    public void sixteenBySixteenSpriteFillsBlock()
+    {
+        var video = new Video();
+        var sprite = new byte[32];
+        for (int index = 0; index < sprite.Length; index++)
+        {
+            sprite[index] = 0xFF;
+        }
+        bool collision = video.drawSprite(sprite, 0, 0, 0, 0, 1, false);
+        Assert.False(collision);
+        Assert.Equal(256, AsciiScreen.litPixelCount(video));
+    }
+}