How to write unit tests for wxWidgets

wxWidgets unit tests use Catch framework. It is included in wxWidgets as a submodule, so you will need to run

$ git submodule update --init 3rdparty/catch

to get it before the first use. Catch is header-only and doesn't need to be compiled.

Building the tests

Before starting modifying the tests, please make sure you can build the existing tests. This requires having built the library itself successfully first and the way to build the test must correspond to the way you used to build the library:

When using MSVS under MSW: just open the provided tests/test_vcX.sln (for non-GUI tests) or tests/test_gui_vcX.sln (for the GUI ones) solution file (where X corresponds to the version of MSVS you use, e.g. 16 for MSVS 2019) and build it in the configuration of your choice.
When using configure under Unix or in a Unix-like environment, such as MSYS: go to the tests subdirectory under the build directory (i.e. the directory where you ran configure, not the one in the source tree) and run make test (non-GUI tests) or make test_gui (GUI ones) to build.
When using CMake, add -DwxBUILD_TESTS=ON (or =CONSOLE for non-GUI tests only) to the command line arguments, or choose the desired wxBUILD_TESTS option in cmake-gui.
When using makefile.vc or makefile.gcc under MSW to build the libraries, use the same makefile under tests to build the tests.

Once the tests were built successfully, you can run them to check that everything works correctly by simply launching the corresponding test binary. See the last subsection for more details about running the tests.

Testing with Catch

WARNING: Most of the existing tests are currently still written in the CppUnit style, please do not follow them when writing new tests, the old style is too complex and unnecessary.

Writing tests with Catch is almost embarrassingly simple: you need to just add a new test case and use Catch assertion macros inside it, e.g.

TEST_CASE("MyNewTest", "[my][new][another-tag]")
{
    wxString s("Hello, world!");
    CHECK( s.BeforeFirst(",") == "Hello" );
    CHECK( s.AfterLast(" ") == "world!" );
}

This is all, the new test will be automatically run when you run the full test suite or you can run just it using

$ ./test MyNewTest

(see below for more about running tests).

See Catch tutorial for more information.

Tests physical structure

All (i.e. both GUI and non-GUI) unit tests are under tests subdirectory. When adding a new test, try to find an existing file to add it to. If there are no applicable files, try to add a new file to an existing directory. If there is no applicable directory neither, create a new one and put the new file there (i.e. do not put new files directly under tests). If your test is small, consider adding it to tests/misc/misctests.cpp.

If you add a new file, you need to update tests/test.bkl and add a <sources> tag for your new file.bkl. Make sure it's in the correct section: the one starting <exe id="test_gui" for a gui test, the one starting <exe id="test" template="wx_sample_console otherwise. After modifying this file, rerun bakefile to regenerate the tests make- and project files:

$ cd build/bakefiles
$ bakefile_gen -b ../../tests/test.bkl

Writing GUI-specific tests

wxUIActionSimulator can be used when user input is required, for example clicking buttons or typing text. A simple example of this can be found in tests/controls/buttontest.cpp. After simulating some user input always call wxYield() to allow event processing. When writing a test using wxUIActionSimulator wrap it in #if wxUSE_UIACTIONSIMULATOR block.

There are a number of classes that are available to help with testing GUI elements. Firstly throughout the test run there is a frame of type wxTestableFrame that you can access through wxTheApp->GetTopWindow(). This class adds two new functions, GetEventCount(), which takes an optional wxEventType. It then returns the number of events of that type that it has received since the last call. Passing nothing returns the total number of event received since the last call. Also there is OnEvent(), which counts the events based on type that are passed to it. To make it easy to count events there is also a new class called EventCounter which takes a window and event type and connects the window to the top level wxTestableFrame with the specific event type. It disconnects again once it is out of scope. It simply reduces the amount of typing required to count events.

Running the tests

Run the main test suite by using the command test for the console tests, or test_gui for the GUI ones. With no arguments, all the default set of tests (all those registered without [hide] tag) are run.

To list the test suites without running them use -l command-line option.

To run a particular test case, use ./test NameTestCase. To run all tests using the specified tag, use ./test [tag_name] (the square brackets may need to be escaped from your shell).

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