This is a Java library allowing you to get data from public transport providers. Look into NetworkProvider.java for an overview of the API.
For some providers a secret like an API key is required to use their API.
Copy the secrets.properties.template file to secrets.properties like so:
$ cp test/de/schildbach/pte/live/secrets.properties.template test/de/schildbach/pte/live/secrets.properties
You need to request the secrets directly from the provider. For Navitia based providers, you can request a secret here.
Make sure the test you want to run does not require a secret and if it does, see above for how to get one. Once you have the secret or if your provider does not need one, you can run the tests in your IDE. Both IntelliJ and Eclipse have excellent support for JUnit tests.
If you prefer to run tests from the command line, you can comment out the test exclude at the end of build.gradle and use this command to only execute a test for a single provider:
$ gradle -Dtest.single=ParisProviderLive test
This uses the ParisProvider as an example.
Just replace it with the provider you want to test.