stmllr.net

One of the key functionality of BackHub is storing data to disk. The BackHub application and its I/O methods are covered by Rspec tests. Unfortunately we can’t use fakefs/fakefs in certain cases to mock the filesystem. Some examples create fixture data, which had to be wiped from the disk afterwards. In general this gets done by our Continuous Integration Server. However, on the developers machines, the CI routines are not fully in place and a cleanup routine was required as a workaround. The routine should wipe any fixtures, except for failed tests, so that developers could examine the test environment.

Solution: Hook into Rspec and delete fixtures if the test passed

The after hook in Rspec can be used for triggering cleanup routines. To avoid conflicts between examples, we perform cleanups after each example, using the after :example hook. Its block is called at the end of each example as a part of the example itself.

after :example do
  # do stuff here
end

Implementing our routine for wiping the disk was easy:

after :example do
  FileUtils.rm_rf path_to_fixtures
end

However, we do not want to wipe fixtures of failed tests, but of passed tests. Therefore the state of an executed test has to be determined. In Cucumber, this state is queried by using:

# Cucumber hook here...
After do |scenario|
  if scenario.passed? do
    FileUtils.rm_rf path_to_fixtures
  end
end

Rspec also comes with a construct which represents the state of an executed test:

example.execution_result[:status]

But as mentioned above, the after :example hook of Rspec is part of the example itself. Within the hook, the example does not yet have a state, because it has not finished.

Nevertheless we need the current state of an example to decide if fixtures should be deleted or not.

With Rspec 2.7, an API was introduced to ask the example for exceptions which occurred during its execution. Exceptions can be used as an indicator that a test failed:

after :example do |example|
  FileUtils.rm_rf path_to_fixtures unless example.exception
end

Et voilà.