Welcome to Triq -- Trifork QuickCheck for Erlang

Triq (pronounced "Trick Check") is a free alternative to QuviQ eqc. Triq's API is modelled closely after eqc, so I recommend their tutorials and slides for an introduction to QuickCheck. Notice that QuviQ eqc has many features not found in triq, but it is open source licensed under the Apache license. For instance, eqc has features for reporting, management, probably a much better shrinking mechanism, cool C integration, and professional support.

Installation

To use triq, you download the latest version from here, and untar it into your erlang lib directory (typically /usr/local/lib/erlang/lib):

prompt$ cd /usr/local/lib/erlang/lib
propmt$ tar xvzf triq-0.1.0.tgz
...

And you're all set.

Or, checkout the triq source code and soft link / copy into your Erlang lib directory:

prompt$ git clone git://github.com/krestenkrab/triq.git
prompt$ cd triq
prompt$ ln -s . /usr/local/lib/erlang/lib/triq-0.1.0

Next, to use triq, include the header file:

-include_lib("triq/include/triq.hrl").

And you're ready to write property tests. An example property could be:

prop_append() ->
    ?FORALL({Xs,Ys},{list(int()),list(int())},
            lists:reverse(Xs++Ys)
            ==
            lists:reverse(Ys) ++ lists:reverse(Xs)).

To test this property, run triq:check/1, thus:

1> triq:check(prop_append()).
......................................................................
..............................
Ran 100 tests
true
2>

If the test fails, it will try to shrink the result; here is an example:

prop_delete() ->
    ?FORALL(L,list(int()),
        ?IMPLIES(L /= [],
            ?FORALL(I,elements(L),
                ?WHENFAIL(io:format("L=~p, I=~p~n", [L,I]),
                          not lists:member(I,lists:delete(I,L)))))).

Which runs like this:

1> triq:check(triq_tests:prop_delete()).
x....Failed!
L=[4,5,5], I=5

Failed after 5 tests with false
Simplified:
        L = [0,0]
        I = 0
false
2>

You can get the values used for the failing test with counterexample, and reuse the same test values with check/2:

3> A = triq:counterexample(triq_tests:xprop_delete()).
x.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxFailed!
L=[3,2,1,1,1], I=1

Failed after 101 tests with false
Simplified:
	L = [0,0]
	I = 0
[[0,0],0]
4> A.
[[0,0],0]
5> triq:check(triq_tests:xprop_delete(), A).
Failed!
L=[0,0], I=0

Failed after 1 tests with false
Simplified:
	L = [0,0]
	I = 0
false
6>

Modules compiled with the triq.hrl header, auto-export all functions named prop_*, and have a function added called check/0 which runs triq:check/1 on all the properties in the module.

1> mymodule:check().

A handy addition that I use is to also add an eunit test, which tests it:

property_test() -> true == check().

Which can then automatically be run using your favourite eunit runner.

Good luck!