Cannot write file during tests with phpunit

The latest version of my tests writes a config file in the tests folder through my TestCase setup. Some tests will use that file, some tests will delete that file first. Travis doesn’t seem to allow my TestCase to write the file on the disk, which makes my tests fail.

Here is the error message:

file_put_contents(/home/travis/build/godbout/alfred-time/src/../tests/AlfredWorkflowDataFolderMock/config.json): failed to open stream: No such file or directory

Is there anything restriction that I’m not aware of, or is there some setting I’m missing to allow files to be written?