Re: [boost] [Boost.Test] Assertion changes in trunk? [WAS: Call for Review: Boost.Test documentation rewrite]

Subject: Re: [boost] [Boost.Test] Assertion changes in trunk? [WAS: Call for Review: Boost.Test documentation rewrite]
From: Alexander Lamaison (awl03_at_[hidden])
Date: 2014-01-22 05:52:53

Dominique Devienne <ddevienne_at_[hidden]> writes:

> On Wed, Jan 22, 2014 at 11:25 AM, Alexander Lamaison <awl03_at_[hidden]>wrote:
>
>> [...]  As for as I'm aware, the only change is
>> to the assertion macros, which move to a more natural syntax:
>>
>> BOOST_CHECK_EQUAL(a, b) becomes BOOST_TEST(a == b)
>> BOOST_CHECK_LT(a, b) becomes BOOST_TEST(a < b)
>> ... etc.
>> BOOST_REQUIRE_EQUAL(a, b) becomes BOOST_TEST_REQUIRE(a == b)
>> ... etc.
>> BOOST_WARN_EQUAL(a, b) becomes BOOST_TEST_WARN(a == b)
>>
>
> But don't we then miss better messages which actually show the values
> themselves when the assert fails? I do BOOST_CHECK(a == b) only when a and
> b lack the op<<, but otherwise greatly prefer BOOST_CHECK_EQUAL(a, b).

Actually, no.

BOOST_CHECK(a <operator> b) expands to something like:

  bool x = (a <operator> b)
  BOOST_CHECK_IMPL(x, "a <operator> b");

int x = 1;
int y = 2;
BOOST_CHECK(x == y)
>> "Assertion failed (file:line): !(x == y)"

so you lose the information about a and b, and which operator was used
to test their relationship.

BOOST_TEST(a <operator> b), however, cleverly parses a, b and <operator>
from the macro and does something like

  bool x = (a <operator> b)
  BOOST_CHECK_MESSAGE_IMPL(x, "a must be <operator> to b", a, b);

int x = 1;
int y = 2;
BOOST_TEST(x == y)
>> "Assertion failed (file:line): "x must be == to y: 1 != 2"

Obviously, the above is pseudocode nonsense, but you get the idea.

> And what's the point of going from BOOST_REQUIRE(expr) to
> BOOST_TEST_REQUIRE(expr), i.e. make it longer / more typing?

The macros had to change anyway because the behaviour was changing.  The
Boost preferred-practice is to prefix new macros with BOOST_ and the
name of the library, so all new Boost.Test macros should start
BOOST_TEST*.

As 'CHECK' is the assertion level you should use by default, BOOST_TEST
with no suffix gets the 'CHECK' behaviour.  The 'REQUIRE' and 'WARN'
behaviours are chosen by adding the suffix, as before.

Alex

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