updated unit test

src/Infrastructure.Tests/GenericTests.cs

@@ -5,7 +5,7 @@ public class GenericTests
     [Fact]
     public void ValueConvertTest()
     {
-        var value = "7";
+        const string value = "7";
         var convertedValue = Convert<long>(value);
         Assert.Equal(7, convertedValue);
     }
@@ -18,9 +18,9 @@ public class GenericTests
     [Fact]
     public void DefaultValueTest()
     {
-        var value = 0L;
+        const long value = 0L;
         long? nullableValue = null;
         Assert.Equal(default, value);
-        Assert.Equal(null, nullableValue);
+        Assert.Null(nullableValue);
     }
 }