added unittest for B2UserData

Author: ikpil

src/Box2D.NET/B2UserData.cs

@@ -81,7 +81,7 @@ public static B2UserData Signed(long i)
             return new B2UserData(i);
         }
 
-        public static B2UserData Unsinged(ulong u)
+        public static B2UserData Unsigned(ulong u)
         {
             return new B2UserData(u);
         }

test/Box2D.NET.Test/B2UserDataTest.cs

@@ -0,0 +1,97 @@
+using NUnit.Framework;
+using Box2D.NET;
+
+namespace Box2D.NET.Test
+{
+    public class B2UserDataTest
+    {
+        [Test]
+        public void TestEmpty()
+        {
+            var userData = B2UserData.Empty;
+            Assert.That(userData.IsEmpty(), Is.True);
+            Assert.That(userData.GetSigned(), Is.EqualTo(0));
+            Assert.That(userData.GetUnsigned(), Is.EqualTo(0));
+            Assert.That(userData.GetDouble(), Is.EqualTo(0.0));
+            Assert.That(userData.GetRef<object>(), Is.Null);
+        }
+
+        [Test]
+        public void TestSigned()
+        {
+            long value = -1234567890L;
+            var userData = B2UserData.Signed(value);
+            
+            Assert.That(userData.IsEmpty(), Is.False);
+            Assert.That(userData.type, Is.EqualTo(B2UserDataType.Signed));
+            Assert.That(userData.GetSigned(), Is.EqualTo(value));
+            
+            // Default value check
+            Assert.That(userData.GetUnsigned(123), Is.EqualTo(123));
+            Assert.That(userData.GetDouble(1.23), Is.EqualTo(1.23));
+            Assert.That(userData.GetRef<string>(), Is.Null);
+        }
+
+        [Test]
+        public void TestUnsigned()
+        {
+            ulong value = 1234567890UL;
+            var userData = B2UserData.Unsigned(value);
+            
+            Assert.That(userData.IsEmpty(), Is.False);
+            Assert.That(userData.type, Is.EqualTo(B2UserDataType.Unsigned));
+            Assert.That(userData.GetUnsigned(), Is.EqualTo(value));
+            
+            // Default value check
+            Assert.That(userData.GetSigned(-1), Is.EqualTo(-1));
+            Assert.That(userData.GetDouble(1.23), Is.EqualTo(1.23));
+            Assert.That(userData.GetRef<string>(), Is.Null);
+        }
+
+        [Test]
+        public void TestDouble()
+        {
+            double value = 3.14159;
+            var userData = B2UserData.Double(value);
+            
+            Assert.That(userData.IsEmpty(), Is.False);
+            Assert.That(userData.type, Is.EqualTo(B2UserDataType.Double));
+            Assert.That(userData.GetDouble(), Is.EqualTo(value));
+            
+            // Default value check
+            Assert.That(userData.GetSigned(-1), Is.EqualTo(-1));
+            Assert.That(userData.GetUnsigned(123), Is.EqualTo(123));
+            Assert.That(userData.GetRef<string>(), Is.Null);
+        }
+
+        [Test]
+        public void TestRef()
+        {
+            string value = "Hello Box2D";
+            var userData = B2UserData.Ref(value);
+            
+            Assert.That(userData.IsEmpty(), Is.False);
+            Assert.That(userData.type, Is.EqualTo(B2UserDataType.Ref));
+            Assert.That(userData.GetRef<string>(), Is.EqualTo(value));
+            
+            // Default value check
+            Assert.That(userData.GetSigned(-1), Is.EqualTo(-1));
+            Assert.That(userData.GetUnsigned(123), Is.EqualTo(123));
+            Assert.That(userData.GetDouble(1.23), Is.EqualTo(1.23));
+        }
+
+        [Test]
+        public void TestRefTypeMismatch()
+        {
+            string value = "Hello Box2D";
+            var userData = B2UserData.Ref(value);
+            
+            // Trying to get as int (boxed) should return null because stored object is string
+            Assert.That(userData.GetRef<object>(), Is.EqualTo(value));
+            
+            // This cast will fail inside GetRef and return null
+            var intRef = userData.GetRef<B2Body>(); 
+            Assert.That(intRef, Is.Null);
+        }
+    }
+}