[SOLVED] Multiple clauses in EUnit's assertMatch?

Multiple clauses in EUnit's assertMatch?

I am using Erlang's EUnit for unit testing an application.

I want to assert that a certain test value is between 2 and 3. There's no built-in support for this, so I am trying to use a pair of guards, like this:

myTestCase ->
  ?assertMatch({ok, V} when V>2, V<3,
               unitUnderTest() % expected to return 2.54232...
  ).

This tries to use the guard syntax for andalso.

However, this does not work, presumably because Erlang's parser can't tell the difference between multiple guards and multiple arguments to assertMatch. I tried wrapping various things in parentheses, but haven't found anything that works. On the other hand, when I reduce the expression to just one clause, it succeeds.

Is there a way to express multiple clauses here?

Solution

You cannot use commas in the syntax, simply because then ?assertMatch is interpreted as a macro with 3 - or more - parameters, and there is no definition for that. But the syntax andalso and orelse works. Why don't you use :

fok() -> {ok,2.7}.

fko() -> {ok,3.7}.

myTestCase(F) ->
    F1 = fun() -> apply(?MODULE,F,[]) end,
    ?assertMatch({ok, V} when V>2 andalso V<3, F1()).

test:

1> c(test).
{ok,test}
2> test:myTestCase(fok).
ok
3> test:myTestCase(fko).
** exception error: {assertMatch,
                        [{module,test},
                         {line,30},
                         {expression,"F1 ( )"},
                         {pattern,"{ ok , V } when V > 2 andalso V < 3"},
                         {value,{ok,3.7}}]}
     in function  test:'-myTestCase/1-fun-1-'/1 (test.erl, line 30)
4>