Re: [Boost-users] unit test BOOST_CHECK_CLOSE absolute

Subject: Re: [Boost-users] unit test BOOST_CHECK_CLOSE absolute
From: lepere renaud (lepere.renaud_at_[hidden])
Date: 2015-01-14 16:26:15

>> For example, I am comparing coordinates in 2d spaces and the relative
>> value is not important, the meaningfull value is the absolute difference
>> between coordinates.
>
> It is almost never true. Related error gives you much better estimate of
> closeness.

I agree with that most of the time but this is not always true. Just 
imagine the case you compare lattitude, longitude. In this case, only 
absolute values make sense.

>
>> I have seen that I can do a
>> BOOST_CHECK_SMALL(fabs(x - expected_x), 1e-3);
>>
>> but in this can I don't have a good message when the test fails (it does
>> not show the value of x and the expected_x).
>>
>> In fact I would like to have something like BOOST_CHECK_CLOSE_ABSOLUTE ?
>> Is there something equivalent or how can I do something like this ?
>
> Don't. Specify relative tolerance (or percent tolerance) and keep using
> BOOST_CHECK_CLOSE.

Relative tolerance will give me false bug report, I want a point to be 
equal to (0, 0) with a small absolute error and I don't care if it is 
-1e-15 or +1e-10 so BOOST_CHECK_CLOSE is not an option here and I have 
to use BOOST_CHECK_SMALL with the absolute difference.

The problem with
BOOST_CHECK_SMALL(fabs(x - expected_x), 1e-3);

Is that when it fails with the message that does not print the values 
"x" and "expected_x" and does not say something like
x(2.0) is not equal to "expected_x(0.0)" with an difference of 1e-3.

I can probably write my own macro combining BOOST_TEST_MESSAGE() and 
some glues to obtain what I want but I was wondering if someone had the 
same problem and a solution.

Thanks

Renaud