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How should a test program report errors? Displaying an error message is an obvious possibility:
if( something_bad_detected ) std::cout << "something bad has been detected" << std::endl;
But that requires inspection of the program's output after each run to determine if an error occurred. Since test programs are often run as part of a regression test suite, human inspection of output to detect error messages is time consuming and unreliable. Test frameworks like GNU/expect can do the inspections automatically, but are overly complex for simple testing.
          A better simple way to report errors is for the test program to return
          EXIT_SUCCESS (normally
          0) if the test program completes satisfactorily, and EXIT_FAILURE
          if an error is detected. This allows a simple regression test script to
          automatically and unambiguously detect success or failure. Further appropriate
          actions such as creating an HTML table or emailing an alert can be taken
          by the script, and can be modified as desired without having to change
          the actual C++ test programs.
        
          A testing protocol based on a policy of test programs returning EXIT_SUCCESS or EXIT_FAILURE
          does not require any supporting tools; the C++ language and standard library
          are sufficient. The programmer must remember, however, to catch all exceptions
          and convert them to program exits with non-zero return codes. The programmer
          must also remember to not use the standard library assert() macro for test code, because on some
          systems it results in undesirable side effects like a message requiring
          manual intervention.
        
          The Boost Test Library's Unit Test Framework is designed to automate those
          tasks. The library supplied main() relieves users from messy error detection
          and reporting duties. Users could use supplied testing tools to perform
          complex validation tasks. Let's take a look on the following simple test
          program:
        
#include <my_class.hpp> int main( int, char* [] ) { my_class test_object( "qwerty" ); return test_object.is_valid() ? EXIT_SUCCESS : EXIT_FAILURE; }
There are several issues with above test.
is_valid
              result in proper result code.
            is_valid invocation, the program
              will crash.
            The Unit Test Framework solves all these issues. To integrate with it above program needs to be changed to:
#include <my_class.hpp> #defineBOOST_TEST_MODULEMyTest #include <boost/test/unit_test.hpp>BOOST_AUTO_TEST_CASE( my_test ) { my_class test_object( "qwerty" ); BOOST_TEST( test_object.is_valid() ); }
          Now, you not only receive uniform result code, even in case of exception,
          but also nicely formatted output from BOOST_TEST tool, would you choose
          to see it. Is there any other ways to perform checks? The following example
          test program shows several different ways to detect and report an error
          in the add()
          function.
        
#defineBOOST_TEST_MODULEMyTest #include <boost/test/unit_test.hpp> int add( int i, int j ) { return i + j; }BOOST_AUTO_TEST_CASE(my_test) { // six ways to detect and report the same error: // continues on errorBOOST_TEST( add(2, 2) == 4 );// throws on error
BOOST_TEST_REQUIRE( add(2, 2) == 4 );//continues on error if (add(2, 2) != 4)
BOOST_ERROR( "Ouch..." );// throws on error if (add(2, 2) != 4)
BOOST_FAIL( "Ouch..." );// throws on error if (add(2, 2) != 4) throw "Ouch...";
// continues on error
BOOST_TEST( add(2, 2) == 4,"2 plus 2 is not 4 but " << add(2, 2)); }
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              This approach uses tool  | |
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              This approach uses tool  | |
| This approach is similar to approach #1, except that the error detection and error reporting are coded separately. This is most useful when the specific condition being tested requires several independent statements and/or is not indicative of the reason for failure. | |
| This approach is similar to approach #2, except that the error detection and error reporting are coded separately. This is most useful when the specific condition being tested requires several independent statements and/or is not indicative of the reason for failure. | |
| 
              This approach throws an exception, which will be caught and reported
              by the Unit Test Framework. The error message
              displayed when the exception is caught will be most meaningful if the
              exception is derived from  | |
| 
              This approach uses tool  |