The file config.app (where app is the short name of your system under test) is central. The location of this file should be set as the TEXTTEST_ROOT environment variable, or specified with the -d flag when you start texttest:
texttest -d /path/to/config/file/directory
For example, if your config file is called config.hello and is located in a folder /users/emily/workspace/hello:
texttest -d /users/emily/workspace/hello
Sometimes you store the test suite in a different location to the system under test (typically for systems where the sourcecode is spread over several git repositories, and you have a separate repo for end-to-end tests). In that case you will need to also specify the path to the system under test using TEXTTEST_CHECKOUT or the -c command line flag when you start texttest:
texttest -d /path/to/config/file/directory -c /path/to/system/under/test/directory
For example, if your config file is called config.hello and is located in a folder /users/emily/workspace/hello, and your system under test is located in :