EmailTest.cs

[Trait("Category", "Domain")]
public class EmailTest
{
    [Fact]
    public void ToString_Email_String()
    {
        var expected = "foo@domain.com";
        var email = new Email(expected);
        var actual = email.ToString();

        Assert.Equal(expected, actual);
    }

    [Fact]
    public void ToEmail_String_Email()
    {
        var expected = "foo@domain.com";
        var actual = Email.ToEmail(expected);

        Assert.Equal(expected, actual.EmailAddress);
    }

    [Theory]
    [InlineData("foo@domain.com")]
    [InlineData("foo.foo@domain.com")]
    [InlineData("a@b.c")]
    public void Email_ValidEmailAddress_Valid(string emailAddress)
    {
        Assert.DoesNotThrows(() => new Email(emailAddress));
    }

    [Theory]
    [InlineData("foo@.com")]
    [InlineData("@.com")]
    [InlineData("foo@com")]
    [InlineData("@domain.com")]
    [InlineData("foo@domain,com")]
    public void Email_InvalidEmailAddress_Invalid(string emailAddress)
    {
        Assert.Throws<FormatException>(() => new Email(emailAddress));
    }
}