lest_expect_assert

Expect assert assertions

This extension lets you assert assertions. It works by substituting assert from the standard library with a version of our own and throwing an exception when the assertion failed [1].

There are two versions of this extension:

• lest_expect_assert.hpp - for C++11 and higher
• lest_expect_assert_cpp03.hpp - for C++98/03 and higher

Please note the following:

• For C++11 and higher, throwing an assertion-failed exception makes it impossible to verify assertions that live in or beneath functions that are specified as noexcept. If your code uses a macro to specify noexcept, you may be able to substitute nothing for it for the tests [2]. Otherwise this extension is of limited use with C++11 and higher.
• For Visual C++, if the assertion-failed exception travels through a C function, the code must be compiled without the 'c' (extern "C" defaults to nothrow) in option -EHsc.

Instrument code in .cpp files

To activate lest's assertion mechanism in your .cpp code, you must include lest_assert.hpp to provide assert(). The assertion mechanism of lest is active whether NDEBUG is defined or not. See also Feature control macros.

Assertion macros

lest_EXPECT_NO_ASSERT( expr ) Evaluate the expression and expect that assert is not called. If assert() is called or if an exception (of any type) is thrown it reported and counted as a failure.

lest_EXPECT_ASSERTS( expr ) Evaluate the expression and expect that assert is called. If assert() is not called or if an exception (of any type) is thrown it is reported and counted as a failure.

Feature control macros

lest_FEATURE_ASSERT=1 Define this to 0 to disable lest's assertion mechanism and let lest_assert.hpp provide <cassert>'s mechanism instead. Default, lest_FEATURE_ASSERTis 1.

Example usage

#if __cplusplus >= 201103 || _MSC_VER >= 1800
# include "lest/lest_expect_assert.hpp"
#else
# include "lest/lest_expect_assert_cpp03.hpp"
#endif

#define CASE( name ) lest_CASE( specification, name )

static lest::tests specification;

CASE( "Expect_asserts succeeds for assert(false) " "[pass]" )
{
    EXPECT_ASSERTS( assert( false ) );
}

int main( int argc, char * argv[] )
{
    return lest::run( specification, argc, argv /*, std::cout */ );
}

Compile and run

Using g++:

prompt>g++ -Wall -Wextra -std=c++11 -Dlest_FEATURE_AUTO_REGISTER=1 -I.. -I../../../include -o 00_basic.exe 00_basic.cpp && 00_basic.exe --pass
00_basic.cpp:15: passed: asserted: Expect_asserts succeeds for assert(false) [pass]: assert( false )
All 1 selected test passed.

With VC14 (VS2015):

prompt>cl -EHsc -Dlest_FEATURE_AUTO_REGISTER=1 -I.. -I../../../include 00_basic.cpp && 00_basic.exe --pass
...
00_basic.cpp(15): passed: asserted: Expect_asserts succeeds for assert(false) [pass]: assert( false )
All 1 selected test passed.

Notes

[1] A previous version of this extension used setjmp() and longjmp() for flow control. However this mechanism doesn't mix well with C++ as it completely subverts stack unwinding and thus exception handling and object destruction.

[2] Visual C++ 14 (Visual Studio 2015) does not let you #define noexcept /*empty*/. Besides it would be hard to also hide noexcept expressions.

Appendix A: Test specification

Issuing command example\00-specification.exe -l @ gives the following listing of the test specification:

Expect_asserts succeeds for assert(false) [pass]
Expect_asserts reports assert(true) [fail]
Expect_asserts succeeds for assert(false) in non-noexcept function [pass]
Expect_asserts terminates for assert(false) in noexcept function [.pass]
Expect_asserts reports an unexpected standard exception [fail]
Expect_asserts reports an unexpected non-standard exception [fail]
Expect_no_assert succeeds for assert(true) [pass]
Expect_no_assert reports assert(false) [fail]
Expect_no_assert reports an unexpected standard exception [fail]
Expect_no_assert reports an unexpected non-standard exception [fail]