On 7/24/17 11:13 PM, NoBigDeal256 wrote:
On Tuesday, 25 July 2017 at 02:18:41 UTC, Adam D. Ruppe wrote:
On Tuesday, 25 July 2017 at 02:11:20 UTC, NoBigDeal256 wrote:
it passes when it should fail because the unittest block is never
executed. Why is this?
Did you actually instantiate the class somewhere? A template has no
concrete code unless created with an argument somewhere...
What if it's instantiated in another module? Right now I'm having issues
where if I run 'dmd a.d b.d -unittest' and the class template in b.d is
instantiated in a.d and it compiles and the tests inside my class
template run as they should, but when using 'dub test' the tests in my
class template don't run at all as if it isn't instantiated in a.d even
though it is. This is the original issue that I had that prompted me to
create this thread.
There is a whole can of worms to be dealt with if you put unit tests
inside template classes or structs.
For instance:
struct Foo(T)
{
T foo() { return T.init; }
unittest
{
Foo!int f;
assert(is(typeof(f.foo()) == int));
}
}
the unit test is instantiated EVERY TIME Foo is instantiated, so if you
have Foo!int and Foo!string both instantiated, BOTH will run this unit
test. Obviously, there is no need to run both. And yes, user code will
also add unit tests unwittingly to their code.
In some cases, this can be useful. If you write like this:
struct Foo(T)
{
T foo() { return T.init; }
unittest
{
Foo f; // note the lack of !
assert(is(typeof(f.foo()) == T));
}
}
This means that for every instantiation, the unit test is checking that
Foo.foo returns T.
But this comes at a cost. Generally unit tests deal with concrete data,
not abstract concepts. This means, you really only want to unit test for
some instantiations, not all.
In phobos, I did this for RedBlackTree. It works well, in that test
coverage is nearly complete over all integral types of elements.
However, there are drawbacks:
1. RedBlackTree with -unittest *will* add unit tests to user modules
(unavoidable).
2. There are some tricky mechanisms to make it work properly (see the code)
3. It comes back to bite me every once in a while, bugs are filed about
this.
The unfortunate thing is that if you want to have non-templated unit
tests, you have to put them outside the struct itself. This sucks for
documented unit tests, and for tests being close to the thing being
tested. I'd love to have a way to specify that a unit test is really
outside the struct, but still have it written inside. I'm not sure if it
would be accepted though.
-Steve
