test: add tests for INumber<T>.Sign

X10D.Tests/src/Numerics/NumberTests.cs

@@ -0,0 +1,32 @@
+#if NET7_0_OR_GREATER
+using NUnit.Framework;
+using X10D.Math;
+
+namespace X10D.Tests.Numerics;
+
+[TestFixture]
+internal class NumberTests
+{
+    [Test]
+    public void Sign_ShouldReturn1_GivenPositiveNumber()
+    {
+        Assert.That(NumberExtensions.Sign(2), Is.Positive);
+        Assert.That(NumberExtensions.Sign(2), Is.EqualTo(1));
+    }
+
+    [Test]
+    public void Sign_Should0_GivenZero()
+    {
+        Assert.That(NumberExtensions.Sign(0), Is.Not.Positive);
+        Assert.That(NumberExtensions.Sign(0), Is.Not.Negative);
+        Assert.That(NumberExtensions.Sign(0), Is.EqualTo(0));
+    }
+
+    [Test]
+    public void Sign_ShouldReturnNegative1_GivenNegativeNumber()
+    {
+        Assert.That(NumberExtensions.Sign(-2), Is.Negative);
+        Assert.That(NumberExtensions.Sign(-2), Is.EqualTo(-1));
+    }
+}
+#endif