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digitalmars.D - throws or the like

reply bearophile <bearophileHUGS lycos.com> writes:
I don't feel (yet) the need for fancy unittest systems, but in my unittests I
need to assert that something works as specified, for that I use assert(). I
also need to assert that something throws the specified exceptions, for that in
my D libs (that I suggest you to start using, because they are refined enough
now) I have added the following:


/****************************************
Function template that takes as types one or more exception types, and
as argument a (lazy) expression. It returns true if once called the
expression throws one of the specified exception(s).

Examples:
void f(int i) { throw new Excep1("f msg"); }<br>
assert( Throws!(Excep1, Excep2)( f(10) ) );<br>
void bar(int i) {}<br>
assert( Throws!()( bar(10) ) );

The second example asserts that bar doesn't throw exceptions.
*/
bool Throws(TyExceptions...)(lazy void deleg) {
    try
        deleg();
    catch (Exception e) {
        foreach(TyExc; TyExceptions)
            if (cast(TyExc)e !is null) // like C++ dynamic_cast
                return true;
        return false;
    }
    return !TyExceptions.length;
}


The syntax of that Throws is bad still:
assert( Throws!(Exception1, Excep2)(foo(10)) );
assert( Throws!(Exception1, Exception2, ...)(foo(10)) );

Note that I have used that nested syntax because I need the line where the
expected exception isn't thrown.

I'd like something in the D language like:
throws(foo(10), Exception1);
throws(foo(10), Exception1, Exception2, ...);

Later I have found that I use static asserts in my templates/functions, and I
need to unittestes those too, so I'd probably enjoy a static version, able to
catch static asserts etc:

static throws(foo(10), StaticException1);
static throws(foo(10), StaticException1, StaticException2, ...);

So far I haven't found a way to test such static assertions/errors, if you have
suggestions I'd love to hear them.

Bye,
bearophile
Apr 21 2008
next sibling parent Sean Kelly <sean invisibleduck.org> writes:
== Quote from bearophile (bearophileHUGS lycos.com)'s article
 I don't feel (yet) the need for fancy unittest systems, but in my unittests I
need to assert that something

exceptions I think an argument could be made for adding some functionality related to this to contracts. Either extend the functionality of the "out" clause, or add a "throw" clause as well. Your template example is pretty cool, however. Sean
Apr 21 2008
prev sibling parent Christopher Wright <dhasenan gmail.com> writes:
bearophile wrote:
 Later I have found that I use static asserts in my templates/functions, and I
need to unittestes those too, so I'd probably enjoy a static version, able to
catch static asserts etc:
 
 static throws(foo(10), StaticException1);
 static throws(foo(10), StaticException1, StaticException2, ...);
 
 So far I haven't found a way to test such static assertions/errors, if you
have suggestions I'd love to hear them.

template template_throws(alias theTemplate, Args...) { // If you have d2, you can use: // static if (__traits(compiles, theTemplate!(Args))) static if (is (typeof (theTemplate!(Args)))) { enum template_throws = false; } else { enum template_throws = true; } } template Foo(int i) { static assert (i > 1); const Foo = i; } static assert (template_throws!(Foo, 1)); static assert (!template_throws!(Foo, 2)); I don't see any static exceptions in D, so I can't handle them.
 Bye,
 bearophile

Apr 24 2008