[/
 / Copyright (c) 2003 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:test_module_init_overview Test module's initialization]

In order for a unit test module to successfully link and execute, it has to have access to the ['test module's initialization function]. the module's initialization function is called only once during the execution of the program, just before the [link boost_test.adv_scenarios.test_module_runner_overview ['test module runner]] is run. By default, the __UTF__ provides a default definition of initialization function. The only thing you have to do is to instruct the framework in which translation unit (`cpp` file) it needs to provide the definition. You do it by defining macro __BOOST_TEST_MODULE__ in the designated file. The default implementation assigns the name to the [link ref_test_module test module] as well as the [link boost_test.tests_organization.test_suite.master_test_suite master test suite]. The name to be assigned is specified by the value of the macro __BOOST_TEST_MODULE__.

[important
For a test module consisting of multiple source files you have to define __BOOST_TEST_MODULE__ in a single test file only.
Otherwise you end up with multiple instances of the initialization function.
]

There is practically no need to ever alter the default behavior of the test module's initialization function. The __UTF__ provides superior tools for performing customization tasks:

* for automatic registration of test cases and test suites in the test tree, see section [link boost_test.tests_organization Tests organization];
* in order to assign the custom name to the master test suite define macro __BOOST_TEST_MODULE__ to desired value;
* in order to access the command-line parameters (except the ones consumed by the __UTF__), use the interface of the [link boost_test.tests_organization.test_suite.master_test_suite master test suite];
* in order to perform a global initialization of the state required by the test cases, [link boost_test.tests_organization.fixtures.global global fixtures] offer a superior alternative: you can specify global set-up and tear-down in one place, allow access to the global data from every test case, and guarantee that clean-up and tear-down is repeated each time the tests are re-run during the execution of the program;
* if the need for custom module initialization is only driven by legacy code (written against old versions of the __UTF__), it is recommended to update your program's code.

The default initialization function provided by the framework is defined with the following signature in the global namespace:

```
bool init_unit_test();
```

Return value `true` indicates a successful initialization. Value `false` indicates initialization failure.

For overriding the default definition:

* [link boost_test.adv_scenarios.single_header_customizations.init_func see here], for single header usage variant,
* [link boost_test.adv_scenarios.static_lib_customizations.init_func see here], for static library usage variant,
* [link boost_test.adv_scenarios.shared_lib_customizations.init_func see here], for shared library usage variant.

[endsect] [/section:test_module_init_overview]
