Question

I’m just getting stated with boost-test and unit testing in general with a new application, and I am not sure how to handle the applications initialisation (eg loading config files, connecting to a database, starting an embedded python interpretor, etc).

I want to test this initialisation process, and also most of the other modules in the application require that the initialisation occurred successfully.

Some way to run some shut down code would also be appreciated.

How should I go about doing this?

Answer 1

It seems what you intent to do is more integration test than unit-test. It’s not to pinpoint on wording, but it makes a difference. Unit testing mean testing methods in isolation, in an environment called a fixture, created just for one test, end then deleted. Another instance of the fixture will be re-created if the next case require the same fixture. This is done to isolate the tests so that an error in one test does not affect the outcome of the subsequent tests.

Usually, one test has three steps:

• Arrange – prepare the fixture : instantiate the class to be tested, possibly other objects needed
• Act – call the method to be tested
• Assert – verify the expectations

Unit tests typically stays away of external resources such as files and databases. Instead mock objects are used to satisfy the dependencies of the class to be tested.

However, depending on the type of your application, you can try to run tests from the application itself. This is not “pure” unit testing, but can be valuable anyway, especially if the code has not been written with unit testing in mind, it might not be “flexible” enough to be unit tested.

This need a special execution mode, with a “-test” parameter for instance, which will initialize the application normally, and then invoke tests that will simulate inputs and use assertions to verify the application reacted as expected. Likewise, it might be possible to invoke the shutdown code and verify with assertions if the database connection has be closed (if the objects are not deleted).

This approach has several drawbacks compared to unit tests: it depends on the config files (the software may behave differently depending on the parameters), on the database (on its content and on the ability to connect to it), the tests are not isolated … The two first can be overcome using default values for the configuration and connecting to a test database in test mode.