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| </a><b>Custom predicate support</b> |
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| <a name="utf.testing-tools.custom-predicate"></a>Custom predicate support</h4></div></div></div> |
| <p class="first-line-indented"> |
| Even though supplied testing tools cover wide range of possible checks and provide detailed report on cause of error |
| in some cases you may want to implement and use custom predicate that perform complex check and produce intelligent |
| report on failure. To satisfy this need testing tools implement custom predicate support. There two layers of custom |
| predicate support implemented by testing tools toolbox: with and without custom error message generation. |
| </p> |
| <p class="first-line-indented"> |
| The first layer is supported by BOOST_CHECK_PREDICATE family of testing tools. You can use it to check any custom |
| predicate that reports the result as boolean value. The values of the predicate arguments are reported by the tool |
| automatically in case of failure. |
| </p> |
| <div class="example"> |
| <a name="utf.testing-tools.custom-predicate.example30"></a><p class="title"><b>Example 36. Custom predicate support using BOOST_CHECK_PREDICATE</b></p> |
| <div class="example-contents"> |
| <pre class="programlisting">#define BOOST_TEST_MODULE example |
| #include <boost/test/included/unit_test.hpp> |
| |
| //____________________________________________________________________________// |
| |
| bool is_even( int i ) { return i%2 == 0; } |
| |
| BOOST_AUTO_TEST_CASE( test_is_even ) |
| { |
| BOOST_CHECK_PREDICATE( is_even, (14) ); |
| |
| int i = 17; |
| BOOST_CHECK_PREDICATE( is_even, (i) ); |
| } |
| |
| //____________________________________________________________________________// |
| |
| </pre> |
| <table class="simplelist" border="0" summary="Simple list"><tr> |
| <td><code class="literal"><a href="../../../src/examples/example30.cpp" target="_top">Source code</a></code></td> |
| <td> | </td> |
| <td><code class="literal"><a href="#" target="_top" id="id658382" onclick="toggle_element( 'example30-output', 'id658382', 'Show output', 'Hide output' ); return false;">Show output</a></code></td> |
| </tr></table> |
| <pre class="example-output" id="example30-output">> example |
| Running 1 test case... |
| test.cpp(13): error in "test_is_even": check is_even( i ) failed for ( 17 ) |
| |
| *** 1 failure detected in test suite "example" |
| </pre> |
| </div> |
| </div> |
| <br class="example-break"><p class="first-line-indented"> |
| To use second layer your predicate have to return |
| <code class="computeroutput">boost::test_tools::predicate_result</code>. This class encapsulates boolean result value along |
| with any error or information message you opt to report. |
| </p> |
| <p class="first-line-indented"> |
| Usually you construct the instance of class <code class="computeroutput">boost::test_tools::predicate_result</code> inside your |
| predicate function and return it by value. The constructor expects one argument - the boolean result value. The |
| constructor is implicit, so you can simply return boolean value from your predicate and |
| <code class="computeroutput">boost::test_tools::predicate_result</code> is constructed automatically to hold your value and empty |
| message. You can also assign boolean value to the constructed instance. You can check the current predicate value by |
| using <code class="computeroutput">operator!</code>() or directly accessing public read-only property p_predicate_value. The |
| error message is stored in public read-write property p_message. |
| </p> |
| <div class="example"> |
| <a name="utf.testing-tools.custom-predicate.example31"></a><p class="title"><b>Example 37. Custom predicate support using class predicate_result</b></p> |
| <div class="example-contents"> |
| <pre class="programlisting">#define BOOST_TEST_MODULE example |
| #include <boost/test/included/unit_test.hpp> |
| |
| //____________________________________________________________________________// |
| |
| boost::test_tools::predicate_result |
| compare_lists( std::list<int> const& l1, std::list<int> const& l2 ) |
| { |
| if( l1.size() != l2.size() ) { |
| boost::test_tools::predicate_result res( false ); |
| |
| res.message() << "Different sizes [" << l1.size() << "!=" << l2.size() << "]"; |
| |
| return res; |
| } |
| |
| return true; |
| } |
| |
| //____________________________________________________________________________// |
| |
| BOOST_AUTO_TEST_CASE( test_list_comparizon ) |
| { |
| std::list<int> l1, l2; |
| l1.push_back( 1 ); |
| l1.push_back( 2 ); |
| |
| BOOST_CHECK( compare_lists( l1, l2 ) ); |
| } |
| |
| //____________________________________________________________________________// |
| |
| </pre> |
| <table class="simplelist" border="0" summary="Simple list"><tr> |
| <td><code class="literal"><a href="../../../src/examples/example31.cpp" target="_top">Source code</a></code></td> |
| <td> | </td> |
| <td><code class="literal"><a href="#" target="_top" id="id658525" onclick="toggle_element( 'example31-output', 'id658525', 'Show output', 'Hide output' ); return false;">Show output</a></code></td> |
| </tr></table> |
| <pre class="example-output" id="example31-output">Running 1 test case... |
| test.cpp(28): error in "test_list_comparizon": check compare_lists( l1, l2 ) failed. Different sizes [2!=0] |
| |
| *** 1 failure detected in test suite "example" |
| </pre> |
| </div> |
| </div> |
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