tests for LCM & GCD

tests/ImageSharp.Tests/Helpers/ImageMathsTests.cs

@@ -0,0 +1,40 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests.Helpers
+{
+    public class ImageMathsTests
+    {
+        [Theory]
+        [InlineData(1, 1, 1)]
+        [InlineData(1, 42, 1)]
+        [InlineData(10, 8, 2)]
+        [InlineData(12, 18, 6)]
+        [InlineData(4536, 1000, 8)]
+        [InlineData(1600, 1024, 64)]
+        public void GreatestCommonDivisor(int a, int b, int expected)
+        {
+            int actual = ImageMaths.GreatestCommonDivisor(a, b);
+
+            Assert.Equal(expected, actual);
+        }
+
+        [Theory]
+        [InlineData(1, 1, 1)]
+        [InlineData(1, 42, 42)]
+        [InlineData(3, 4, 12)]
+        [InlineData(6, 4, 12)]
+        [InlineData(1600, 1024, 25600)]
+        [InlineData(3264, 100, 81600)]
+        public void LeastCommonMultiple(int a, int b, int expected)
+        {
+            int actual = ImageMaths.LeastCommonMultiple(a, b);
+
+            Assert.Equal(expected, actual);
+        }
+
+        // TODO: We need to test all ImageMaths methods!
+    }
+}