added unit test

src/Infrastructure.Tests/GenericTests.cs

@@ -14,4 +14,13 @@ public class GenericTests
     {
         return (T)System.Convert.ChangeType(value, typeof(T));
     }
+
+    [Fact]
+    public void DefaultValueTest()
+    {
+        var value = 0L;
+        long? nullableValue = null;
+        Assert.Equal(default, value);
+        Assert.Equal(null, nullableValue);
+    }
 }