public void Channel_slug_can_be_parsed_from_a_URL_string(string channelUrl, string expectedChannelSlug)
    {
        // Act
        var parsed = ChannelSlug.Parse(channelUrl);

        // Assert
        parsed.Value.Should().Be(expectedChannelSlug);
    }
 public void Channel_slug_cannot_be_parsed_from_an_invalid_string(string channelSlugOrUrl)
 {
     // Act & assert
     Assert.Throws <ArgumentException>(() => ChannelSlug.Parse(channelSlugOrUrl));
 }