Hints.md

Hints

Test framework

In order to write tests we require some kind of constructs to express the desired behavior. And we should be notified whenever the applications behavior is different.

If you already have a favorite test framework and know how to set it up within cmake, then just use that.

Plain assert

One of the easiest to use frameworks is part of the C++ standard library. You'll find it in #include <cassert> and it provides one single test macro assert.

It has a few drawbacks, but it's a good option to get started fast.

DIY

Another option consists of writing your own simple assert function that throws an exception.

class AssertionFailed : public std::exception {};

void assert_that(bool condition) {
  if(not condition) {
    throw AssertionFailed{};
  }
}

By calling your test functions in loop with a try-catch for each test case, you can print passed or failed for each test case.

Of-the-shelf

Popular options include Catch which provides a simple single header include.

Or GoogleTest which has a lot of functionality.

Write a first test

A high level system test requires two things. Interacting with the application by clicking on start, stop etc. And accessing the text within the application to check its state.

Accessing the widget

Either can be achieved by having access to the QTextBrowser widget variable timerWidget. But we can not just change the variable into a public member variable because of how Qt works. As a workaround replace timerWidget with a std::unique_ptr and initialize and reset at the right places to control the widgets lifetime.

Test helpers

Interacting with the application:

void click(BabystepsTimer const & testee, QString const & command) {
  emit testee._timerWidget->anchorClicked(QString{"command://" + command});
}

Reading its state:

std::string ui_text(BabystepsTimer const & testee) {
  return testee._timerWidget->toPlainText().toStdString();
}

Test and Qt loop threads

The application is started with the exec() method which will block until execution finishes. In order to interact with the application from the test we need a separate thread for either the application or the test:

void BabystepsTimer_is_set_to_two_minutes_when_created) {
  BabystepsTimer testee;

  std::thread test_thread{[&testee] {
    std::this_thread::sleep_for(std::chrono::milliseconds(200));

    assert_that(ui_text(testee).find("02:00") != std::string::npos);

    click(testee, "quit");
  }};

  testee.exec(0, nullptr);
  test_thread.join();
}

Application exit

You may be wondering why the test exits even before the first test has finished.

There is a hard exit(0) when you want to close the application. Replace it with application.quit(); to stop the application without exiting the test executable.