How do I include specs for a base class in the specs for an inherited class?

Question

I have an RSSDataSourceParser class which is fully covered by MSpec specifications. I also have an inherited class, MultimediaRSSDataSourceParser . It does all of the parent functionality plus recognition of iTunes RSS extensions. I covered the extended functionality in separate specifications.

However, the business people who read the test suite only see the extended specifications for the MultimediaRSSDataSourceParser . They want to see the inherited functionality from RSSDataSourceParser , too.

Copying these specifications sounds absurd and would probably cause future code management problems. Is there any way to inherit the specifications from the parent?

Answer 1

MSpec has pretty useful behaviours that make reuse like this pretty easy. http://lostechies.com/jamesgregory/2010/01/18/behaviours-in-mspec/

Answer 2

I image the two types implement the same interface, or are at least inherited, when you say "it does all the parent [functionality]". You want to use MSpec's Behaves_like feature.

"Behaviours define reusable specs that encapsulate a particular set of, you guessed it, behaviours; you're then able to include these specs in any context that exhibits a particular behaviour." -- James Gregory

I don't know how an RSS data source reader works, so let me show you some example code where I used behaviors. I needed to convert an integer power of 2 (0, 1, 2, 4, etc) from some goofy API into an AZ character. So, the specifications would be

It should_convert_0_to_A = () => _converter.Convert(0).ShouldEqual('A');
It should_convert_1_to_B = () => _converter.Convert(1).ShouldEqual('B');
// ... and so on ...
It should_convert_16777216_to_Z = () => _converter.Convert(16777216).ShouldEqual('Z');

But, I had three different implementations of the interface. They included a binary conversion , a log conversion , and a lookup table .

public interface IUnitMaskConverter
{
    char Convert(uint mask);
}

I wasn't going to copy 26 specifications three or more times, So, I set the specs into a Behaviors class

[Behaviors]
public class UnitMaskConverterBehaviors
{
    It should_convert_0_to_A = () => _converter.Convert(0).ShouldEqual('A');
    It should_convert_1_to_B = () => _converter.Convert(1).ShouldEqual('B');
    // ... and so on ...
    It should_convert_16777216_to_Z = () => _converter.Convert(16777216).ShouldEqual('Z');

    protected static IUnitMaskConverter _converter;
}

So, then it's pretty easy to write a specs class that says this implementation behaves like a "unit mask converter"

[Subject(typeof(IUnitMaskConverter))]
public class When_converting_unit_masks_by_lookup
{
    Behaves_like<UnitMaskConverterBehaviors> a_unit_mask_converter;
    protected static LookupUnitMaskConverter _converter = new LookupUnitMaskConverter();
}

[Subject(typeof(IUnitMaskConverter))]
public class When_converting_unit_masks_by_log
{
    Behaves_like<UnitMaskConverterBehaviors> a_unit_mask_converter;
    protected static LogUnitMaskConverter _converter = new LogUnitMaskConverter();
}

[Subject(typeof(IUnitMaskConverter))]
public class When_converting_unit_masks_by_binary
{
    Behaves_like<UnitMaskConverterBehaviors> a_unit_mask_converter;
    protected static BinaryUnitMaskConverter _converter = new BinaryUnitMaskConverter();
}

The report even has all the behaviors listed per implementation.

---

IUnitMaskConverter specifications

4 contexts, 108 specifications

When converting unit masks by binary

26 specifications

• should convert 0 to A
• should convert 1 to B
• ...
• should convert 16777216 to Z

When converting unit masks by lookup

26 specifications

• should convert 0 to A
• should convert 1 to B
• ...
• should convert 16777216 to Z

Answer 3

This is not the case because testsuite for the RssDatasourceParser might be contained from large number of contexts. This means again lots of writing.