Unit test practices in Phobos

Jeremie Pelletier jeremiep at gmail.com
Mon Aug 10 09:54:54 PDT 2009


Lars T. Kyllingstad Wrote:

> I just filed a bug report (3240) that describes a case where IFTI is 
> used in Phobos, and where this causes errors when the function is used 
> with a different type than the one used in the unittest. (The well known 
> "IFTI doesn't work with implicit conversions" problem.) I have a strong 
> suspicion that there are many other cases like this waiting to be 
> discovered.
> 
> I have encountered such errors in my own code many times, and lately 
> I've been trying to get into the habit of writing unittests for all (or 
> at least more than one) types. Not full-fledged functionality tests, 
> mind you -- something like this is usually sufficient:
> 
>    T foo(T)(T x) if (isFloatingPoint!T) { return x + 1.0; }
> 
>    unittest
>    {
>        // Test different types
>        alias foo!float foo_float;
>        alias foo!double foo_double;
>        alias foo!real foo_real;
> 
>        // Test functionality
>        assert (foo(2.0) == 3.0);
>    }
> 
> For the cases where any type is allowed (or a lot of them, at least) 
> even this can become a time-consuming task. In these cases it should at 
> least be possible to make a representative selection of types to check.
> 
> I just wanted to recommend this as "good practice" to all, but 
> especially to the Phobos authors. In my experience this catches a lot of 
> bugs which are otherwise hard to spot.
> 
> -Lars

I just go with type tuples:

T foo(T)(T x) if(isFloatingPoint!T) { return x + 1.0; }
unittest {
    foreach(T; allFloatingPointTuple) assert(foo!T(1.0) == 2.0);
}



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