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 / Copyright (c) 2015 Boost.Test contributors
 /
 / Distributed under the Boost Software License, Version 1.0. (See accompanying
 / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 /]

[section:boost_test_universal_macro BOOST_TEST: universal and general purpose assertions]

The __UTF__ provides an almost unique interface to a great range of test-case scenarios, through the __BOOST_TEST__
macro. The general form of `BOOST_TEST` is the following:

  BOOST_TEST(statement);
  BOOST_TEST_<level>(statement, optional_modifiers)

An example of use might be the following:

[bt_example boost_test_macro_overview..BOOST_TEST overview..run-fail]

The major features of this tool are:

* a great flexibility for `statement` which may be almost anything: full expression composed by several operations are supported
  and handled,
* an extended reporting capability in case of failure: not only `BOOST_TEST` reports the location of the failure and a copy of `statement` itself,
  but also the values of the operands that permits a rapid identification of the issues related to the failed assertion,
* the possibility to control better the behavior or the reports of the checks, in particular:

  * floating point comparison: the tolerance may be provided, either using the `BOOST_TEST`
     directly with `optional_modifiers`, or with /decorators/ (see [link boost_test.testing_tools.extended_comparison.floating_point here]
     for more details),
  * container/collection comparisons: different operations for comparison are provided out of the box for comparing collection of
    elements (default, per-element, lexicographic), with extended diagnostic on failures (covered in
    [link boost_test.testing_tools.extended_comparison.collections this] section),
  * string comparison: C-strings operands are automatically detected and the comparisons are performed as if `std::string` objects
    were used,
  * optional failure message,
  * bitwise comparison, providing extended diagnostic in case of failure

[warning To get all the functionalities of `BOOST_TEST` family of assertions, a C++11 capable compiler is required, especially
 supporting the `auto` and `decltype` keywords and the variadic macros. The documentation focuses on these set of compilers.
 For compilers not supporting all the features of `BOOST_TEST`, the macro `BOOST_TEST_MACRO_LIMITED_SUPPORT`.]

[#boost_test_statement_overloads][h3 Complex statements]
`BOOST_TEST` provides an enhanced reporting capability: additional details of the failing operands and operations are provided in the log,
as shown on the example below:

[bt_example boost_test_macro3..BOOST_TEST enhanced reporting..run-fail]

`BOOST_TEST` parses the `statement` and constructs an expression out of it. `statement` may be a complex expressions
containing almost any of the overloadable operators in C++:

[table
  [[Class of operation][operators]]
  [[binary comparisons][`==`, `!=`, `<`, `>`, `<=`, `>=`]]
  [[arithmetic compositions][`+`, `-`, `*`, `/`, `%`]]
  [[bitwise compositions][`|`, `&`, `^`, `<<`, `>>`]]
  [[assignments][`=`, `+=`, `-=`, `*=`, `/=`, `%=`, `<<=`, `>>=`, `&=`, `^=`, `|=`]]
]

`statement` is evaluated and cast to `bool`, as if it would appear as argument to an `if` statement: this is the result of the assertion

[h3 Uniform reporting]
This tool is provided in three variants corresponding to the corresponding
[link boost_test.testing_tools.tools_assertion_severity_level severity levels]. These three levels of assertions are
reported into the test log and output, as described in details in the section. The granularity of the
report depends on the current [link boost_test.utf_reference.rt_param_reference.log_level log level] and
[link boost_test.utf_reference.rt_param_reference.report_level report level].

[#boost_test_statement_limitations][h3 Limitations & workaround]
There are a few constructions that are however unsupported, but adding an extra bracket usually solves that:

* statements containing ternary conditions: those statement should be surrounded by parenthesis as they cannot be overloaded
* statements containing commas: those statements will be intercepted by the preprocessor
* compound statements containing any logical composition `||`, `&&`. Those are disabled intentionally and should be surrounded
  by parenthesis

    BOOST_TEST((true || false));

  The full details are given in [link boost_test.testing_tools.internal_details this section].

[bt_example boost_test_macro_workaround..BOOST_TEST limitation and workaround..run]


[endsect] [/ boost_test_universal_macro]