test(core): add PPM export and disassembler tests

tests/Chip8.Tests/PpmTests.cs

@@ -0,0 +1,86 @@
+using System.Text;
+using Chip8.Core;
+using Chip8.Core.Export;
+using Xunit;
+
+namespace Chip8.Tests;
+
+public class PpmTests
+{
+    static int headerLength(byte[] ppm)
+    {
+        int newlines = 0;
+        for (int index = 0; index < ppm.Length; index++)
+        {
+            if (ppm[index] == (byte)'\n' && ++newlines == 3)
+            {
+                return index + 1;
+            }
+        }
+        return -1;
+    }
+
+    [Fact]
+    public void monochromeImageHasCorrectHeaderAndSize()
+    {
+        var pixels = new bool[2 * 2];
+        byte[] ppm = PpmImage.fromMonochrome(pixels, 2, 2, Palette.monochrome());
+
+        string header = Encoding.ASCII.GetString(ppm, 0, headerLength(ppm));
+        Assert.Equal("P6\n2 2\n255\n", header);
+        Assert.Equal(headerLength(ppm) + 2 * 2 * 3, ppm.Length);
+    }
+
+    [Fact]
+    public void litAndUnlitPixelsUsePaletteColors()
+    {
+        var pixels = new bool[] { true, false, false, true };
+        var palette = new Palette(new Rgb(1, 2, 3), new Rgb(10, 20, 30));
+        byte[] ppm = PpmImage.fromMonochrome(pixels, 2, 2, palette);
+        int start = headerLength(ppm);
+
+        Assert.Equal(10, ppm[start]);
+        Assert.Equal(20, ppm[start + 1]);
+        Assert.Equal(30, ppm[start + 2]);
+        Assert.Equal(1, ppm[start + 3]);
+        Assert.Equal(2, ppm[start + 4]);
+        Assert.Equal(3, ppm[start + 5]);
+    }
+
+    [Fact]
+    public void scaleMultipliesDimensions()
+    {
+        var pixels = new bool[1];
+        byte[] ppm = PpmImage.fromMonochrome(pixels, 1, 1, Palette.monochrome(), scale: 4);
+        string header = Encoding.ASCII.GetString(ppm, 0, headerLength(ppm));
+        Assert.Equal("P6\n4 4\n255\n", header);
+        Assert.Equal(headerLength(ppm) + 4 * 4 * 3, ppm.Length);
+    }
+
+    [Fact]
+    public void videoExportUsesColorPlanes()
+    {
+        var video = new Video();
+        video.setResolution(true);
+        var sprite = new byte[] { 0x80 };
+        video.drawSprite(sprite, 0, 0, 0, 1, 0x2, false);
+
+        byte[] ppm = PpmImage.fromVideo(video, Palette.octo());
+        int start = headerLength(ppm);
+        Rgb colorTwo = Palette.octo()[2];
+
+        Assert.Equal(colorTwo.r, ppm[start]);
+        Assert.Equal(colorTwo.g, ppm[start + 1]);
+        Assert.Equal(colorTwo.b, ppm[start + 2]);
+    }
+
+    [Fact]
+    public void fromMachinePicksMonochromeForChip8()
+    {
+        var machine = new Machine(Quirks.modern(), 1);
+        machine.display[0] = true;
+        byte[] ppm = PpmImage.fromMachine(machine, Palette.monochrome());
+        int start = headerLength(ppm);
+        Assert.Equal(0xFF, ppm[start]);
+    }
+}