finally

Minint.Tests/CompositorTests.cs

@@ -0,0 +1,76 @@
+using Minint.Core.Models;
+using Minint.Core.Services.Impl;
+
+namespace Minint.Tests;
+
+public class CompositorTests
+{
+    private readonly Compositor _compositor = new();
+
+    [Fact]
+    public void Composite_EmptyLayer_AllTransparent()
+    {
+        var doc = new MinintDocument("test");
+        doc.Layers.Add(new MinintLayer("L1", 4));
+
+        uint[] result = _compositor.Composite(doc, 2, 2);
+
+        Assert.All(result, px => Assert.Equal(0u, px));
+    }
+
+    [Fact]
+    public void Composite_SingleOpaquePixel()
+    {
+        var doc = new MinintDocument("test");
+        var red = new RgbaColor(255, 0, 0, 255);
+        doc.EnsureColorCached(red);
+        var layer = new MinintLayer("L1", 4);
+        layer.Pixels[0] = 1;
+        doc.Layers.Add(layer);
+
+        uint[] result = _compositor.Composite(doc, 2, 2);
+
+        // ARGB packed as 0xAARRGGBB
+        uint expected = 0xFF_FF_00_00u;
+        Assert.Equal(expected, result[0]);
+        Assert.Equal(0u, result[1]); // rest is transparent
+    }
+
+    [Fact]
+    public void Composite_HiddenLayer_Ignored()
+    {
+        var doc = new MinintDocument("test");
+        doc.EnsureColorCached(new RgbaColor(0, 255, 0, 255));
+        var layer = new MinintLayer("L1", 4);
+        layer.Pixels[0] = 1;
+        layer.IsVisible = false;
+        doc.Layers.Add(layer);
+
+        uint[] result = _compositor.Composite(doc, 2, 2);
+
+        Assert.Equal(0u, result[0]);
+    }
+
+    [Fact]
+    public void Composite_TwoLayers_TopOverBottom()
+    {
+        var doc = new MinintDocument("test");
+        var red = new RgbaColor(255, 0, 0, 255);
+        var blue = new RgbaColor(0, 0, 255, 255);
+        int redIdx = doc.EnsureColorCached(red);
+        int blueIdx = doc.EnsureColorCached(blue);
+
+        var bottom = new MinintLayer("bottom", 1);
+        bottom.Pixels[0] = redIdx;
+        var top = new MinintLayer("top", 1);
+        top.Pixels[0] = blueIdx;
+
+        doc.Layers.Add(bottom);
+        doc.Layers.Add(top);
+
+        uint[] result = _compositor.Composite(doc, 1, 1);
+
+        // Blue on top, fully opaque, should overwrite red
+        Assert.Equal(0xFF_00_00_FFu, result[0]);
+    }
+}