Interface property serialization / deserialization using JsonDerivedType

User.cs

[JsonDerivedType(typeof(UnverifiedEmail), nameof(UnverifiedEmail))]
[JsonDerivedType(typeof(VerifiedEmail), nameof(VerifiedEmail))]
public interface IUserEmail;
public record UnverifiedEmail(string Value) : IUserEmail;
public record VerifiedEmail(string Value) : IUserEmail;
public record User(string Name, IUserEmail Email);
public class UserEmailTest
{
    private readonly ITestOutputHelper _testOutputHelper;
    public UserEmailTest(ITestOutputHelper testOutputHelper) => _testOutputHelper = testOutputHelper;
    [Fact]
    public void TestingEmail()
    {
        var user = new User("test", new UnverifiedEmail("[email protected]"));
        var user2 = new User("test", new VerifiedEmail("[email protected]"));
        if (user.Email is VerifiedEmail email)
        {
            SendEmail(email);
        }
        if (user2.Email is VerifiedEmail email2)
        {
            SendEmail(email2);
        }
    }
    private void SendEmail(VerifiedEmail email)
    {
        _testOutputHelper.WriteLine("sending email to " + email.Value + "...");
    }

    [Fact]
    public void SerializationSucceedsTest()
    {
        var test = new User("test", new UnverifiedEmail("[email protected]"));
        var json = JsonSerializer.Serialize(test);
        Assert.NotNull(json);
        Assert.Equal("{\"Name\":\"test\",\"Email\":{\"$type\":\"UnverifiedEmail\",\"Value\":\"[email protected]\"}}", json);
        // Assert.Equal("{\"Name\":\"test\",\"Email\":{\"Value\":\"[email protected]\"}}", json);
    }

    [Fact]
    public void DeserializationNotThrowsTest()
    {
        var test = JsonSerializer.Deserialize<User>("{\"Name\":\"test\",\"Email\":{\"$type\":\"UnverifiedEmail\",\"Value\":\"[email protected]\"}}");
        Assert.NotNull(test);
        Assert.Equal(new User("test", new UnverifiedEmail("[email protected]")), test);
    }
}