Boost C++ Libraries

While in a perfect world all test assertions should pass in order for a test module to pass, in some situations it is desirable to temporarily allow particular tests to fail. For example, where a particular feature is not implemented yet and one needs to prepare a library for the release or when particular test fails on some platforms. To avoid a nagging red box in regression tests table, you can use the expected failures feature.

This feature allows specifying an expected number of failed assertions per test unit. The value is specified during test tree construction, and can't be updated during test execution.

The feature is not intended to be used to check for expected functionality failures. To check that a particular input is causing an exception to be thrown use BOOST_<level>_THROW family of testing tools.

The usage of this feature should be limited and employed only after careful consideration. In general you should only use this feature when it is necessary to force a test module to pass without actually fixing the problem. Obviously, an excessive usage of expected failures defeats the purpose of the unit test. In most cases it only needs be applied temporarily.

You also need to remember that the expected failure specification is per test case. This means that any failed assertion within that test case can satisfy the expected failures quota. Meaning it is possible for an unexpected failure to occur to satisfy this quota.

	Note
	If an assertion at fault is fixed and passed while an expected failures specification still present, the number of failures becomes smaller than expected. The test is going to be reported as passed; instead, a warning message will be issued.

Expected failure specification

The decorator expected_failures defines the number of assertions that are expected to fail within the corresponding test unit. It is reported as failure when the number of failed assertions is greater than the declared expected number of failures. If the number of failed assertions is less than the number of expected failures a message is reported. The total number of expected failures for a given test suite S is the sum of the declared expected failures in S and the sum of expected failures in all nested test units:

Example: decorator expected_failures

#define BOOST_TEST_MODULE decorator_10
#include <boost/test/included/unit_test.hpp>
namespace utf = boost::unit_test;

BOOST_AUTO_TEST_SUITE(suite1,
  * utf::expected_failures(1))

  BOOST_AUTO_TEST_CASE(test1,
    * utf::expected_failures(2))
  {
    BOOST_TEST(false);
    BOOST_TEST(false);
  }

  BOOST_AUTO_TEST_CASE(test2)
  {
    BOOST_TEST(false);
    BOOST_TEST(false);
  }

BOOST_AUTO_TEST_SUITE_END()

> decorator_10
Running 2 test cases...
test.cpp(11): error: in "suite1/test1": check false has failed
test.cpp(12): error: in "suite1/test1": check false has failed
test.cpp(17): error: in "suite1/test2": check false has failed
test.cpp(18): error: in "suite1/test2": check false has failed

*** 4 failures are detected (3 failures are expected) in the test module "decorator_10"


> decorator_10 --run_test=suite1/test1
Running 1 test case...
test.cpp(11): error: in "suite1/test1": check false has failed
test.cpp(12): error: in "suite1/test1": check false has failed

*** No errors detected

In the above example, we first run all test cases with four failed assertions. The total number of expected failures is 3: 1 (for test suite1) + 2 (for test1). Because the expected failure count is exceeded, the error is reported. In the second case, we only run test case suite1/test1: two failures occur, two failures are expected, therefore no error is reported.

Usage with automatically registered test cases

	Caution
	this usage is considered as deprecated. Please consider using the expected_failures decorator instead.

For backwards compatibility, it is possible to indicate the expected failures with BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES ^[15] before the test case definition.

BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES(test_case_name, number_of_expected_failures);

You can use this macro both on a file scope and inside a test suite. Moreover you can use it even if name of test units coincide in different test suites. Expected failures specification applies to the test unit belonging to the same test suite where BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES resides.

Example: Expected failures specification for automatically registered test case

#define BOOST_TEST_MODULE example
#include <boost/test/included/unit_test.hpp>

BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES( my_test1, 1 )

BOOST_AUTO_TEST_CASE( my_test1 )
{
  BOOST_TEST( 2 == 1 );
}

BOOST_AUTO_TEST_SUITE( internal )

BOOST_AUTO_TEST_CASE_EXPECTED_FAILURES( my_test1, 2 )

BOOST_AUTO_TEST_CASE( my_test1 )
{
  BOOST_CHECK_EQUAL( sizeof(int), sizeof(char) );
  BOOST_CHECK_EQUAL( sizeof(int*), sizeof(char) );
}

BOOST_AUTO_TEST_SUITE_END()

> example --report_level=short
Running 2 test cases...
test.cpp(10): error in "my_test1": check 2 == 1 has failed
test.cpp(21): error in "my_test1": check sizeof(int) == sizeof(char) has failed [4 != 1]
test.cpp(22): error in "my_test1": check sizeof(int*) == sizeof(char) has failed [4 != 1]

Test suite "example" passed with:
  3 assertions out of 3 failed
  3 failures expected
  2 test cases out of 2 passed

Usage with manually registered test cases

	Caution
	this usage is considered as deprecated. Please consider using the expected_failures decorator instead.

To set the value of expected failures for the manually registered test unit pass it as a second argument for the test_suite::add call during test unit registration.

Example: Expected failures specification for manually registered test case

#include <boost/test/included/unit_test.hpp>
using namespace boost::unit_test;

void free_test_function()
{
  BOOST_TEST( 2 == 1 );
}

test_suite* init_unit_test_suite( int, char* [] )
{
  framework::master_test_suite().
    add( BOOST_TEST_CASE( &free_test_function ), 2 );

  return 0;
}

> example --log_level=message
Running 1 test case...
test.cpp(8): error in "free_test_function": check 2 == 1 has failed
Test case has less failures then expected

*** No errors detected