test.cs

[Fact]
public void CheckIfAllClassesInNamespaceHavePropertiesWithVirtualKeyword()
{
    var assembly = Assembly.GetAssembly(typeof(User));
    var @namespace = typeof(User).Namespace;
    var typesInNamespace = GetTypesInNamespace(assembly, @namespace);
 
    foreach (var type in typesInNamespace)
    {
        var properties = type.GetProperties();
        foreach (var property in properties)
        {
            var userMessage = $"{type.FullName}.{property.Name}";
            Assert.True(property.GetGetMethod().IsVirtual, userMessage);
        }
    }
}
 
private Type[] GetTypesInNamespace(Assembly assembly, string nameSpace)
{
    return assembly.GetTypes().Where(t => String.Equals(t.Namespace, nameSpace, StringComparison.Ordinal)).ToArray();
}