Boost C++ Libraries

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`BOOST_<level>_EXCEPTION`

BOOST_WARN_EXCEPTION(expression, exception_type, predicate);
BOOST_CHECK_EXCEPTION(expression, exception_type, predicate);
BOOST_REQUIRE_EXCEPTION(expression, exception_type, predicate);

As for BOOST_<level>_THROW, these assertions validate that expression raises an exception of the type specified by exception_type or any of its child type, with additional checks on the exception instance.

If an expected exception is raised by expression, the instance of the exception is passed to predicate for further validation.
It behaves like BOOST_<level>_THROW if expression does not raise any exception, or an unrelated exception is raised.

predicate should be a unary function accepting an instance of exception_type or any of its child, and that should return a boolean indicating a success (true) or a failure (false).

	Warning
	the assertion catches only the expected exceptions.

	Tip
	It is possible to test for complex expressions with the use of constructs such as `do { /* ... */} while(0)` block.

The example below checks that the exception carries the proper error code.

Example: BOOST_<level>_EXCEPTION usage

Code

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

struct my_exception
{
  explicit my_exception( int ec = 0 ) : m_error_code( ec )
  {}

  int m_error_code;
};

bool is_critical( my_exception const& ex ) { return ex.m_error_code < 0; }

void some_func( int i ) { if( i>=0 ) throw my_exception( i ); }

BOOST_AUTO_TEST_CASE( test_exception_predicate )
{
  BOOST_CHECK_EXCEPTION( some_func(0), my_exception, !is_critical );
  BOOST_CHECK_EXCEPTION( some_func(1), my_exception, is_critical );
}

Output

> example --log_level=success
Running 1 test case...
Entering test module "example"
test:24: Entering test case "test_exception_predicate"
test:26: info: check 'exception "my_exception" raised as expected: validation on the raised exception through predicate "!is_critical"' has passed
test:27: error: in "test_exception_predicate": exception "my_exception" raised as expected: validation on the raised exception through predicate "is_critical"
test:24: Leaving test case "test_exception_predicate"; testing time: 203us
Leaving test module "example"; testing time: 271us

*** 1 failure is detected in the test module "example"

See also:

BOOST_<level>_THROW
Exception correctness section