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41 lines
2.1 KiB
Plaintext
41 lines
2.1 KiB
Plaintext
[/
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/ Copyright (c) 2003-2014 Gennadiy Rozental
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/ Copyright (c) 2013-2014 Raffi Enficiaud
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/
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/ Distributed under the Boost Software License, Version 1.0. (See accompanying
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/ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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/]
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[section:custom_predicates Custom predicate support]
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[def __class_predicate_result__ [classref boost::test_tools::predicate_result]]
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Even though supplied testing tools cover wide range of possible checks and provide detailed report on cause of error
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in some cases you may want to implement and use custom predicate that perform complex check and produce intelligent
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report on failure. To satisfy this need testing tools implement custom predicate support. There two layers of custom
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predicate support implemented by testing tools toolbox: with and without custom error message generation.
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The first layer is supported by __BOOST_LEVEL_PREDICATE__ family of testing tools. You can use it to check any custom
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predicate that reports the result as boolean value. The values of the predicate arguments are reported by the tool
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automatically in case of failure.
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[bt_example example30..Custom predicate support using __BOOST_LEVEL_PREDICATE__]
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To use second layer your predicate has to return __class_predicate_result__.
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This class encapsulates boolean result value along with any error or information message you opt to report.
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Usually you construct the instance of class __class_predicate_result__ inside your
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predicate function and return it by value. The constructor expects one argument - the boolean result value. The
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constructor is implicit, so you can simply return boolean value from your predicate and
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__class_predicate_result__ is constructed automatically to hold your value and empty
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message. You can also assign boolean value to the constructed instance. You can check the current predicate value by
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using `operator!` or directly accessing public read-only property `p_predicate_value`. The
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error message is stored in public read-write property `p_message`.
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[bt_example example31..Custom predicate support using class __class_predicate_result__]
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[endsect] [/predicate]
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