Directories:

1. cassettes/: Location of vcrpy and pytest-recording cassettes.

Files:

1. conftest.py: Location of pytest global and configuration fixtures.
2. utils.py: Location of global Python helper objects (i.e. constants and Ozone instance) to use in tests.
3. test_*.py: Test files, each file is testing one public method.

After setting development environment as pointed out in CONTRIBUTING.md, you should already have all necessary testing packages installed. To run all tests, invoke this command from the root directory.

pytest

Generally, tests should correspond to the necessary specification/expectation of Ozone users. Tests will help us identify if our code is still in line with such expectations.

Tests should be updated when e.g.:

• There is a new functionality. In this case, add necessary tests accordingly.
• There is a change in existing functionality that is in line with the expectation of Ozone users. In this case, the tests become outdated and need to be updated.
• There is a new bug or previously unencountered or undocumented behavior. Add them to the existing tests to make sure the same bug will never slip past again in the future.

This test suite is testing Ozone's functionality, so interaction with outside sources need to be mocked. Ozone uses pytest-recording plugin that uses vcrpy under the hood to record request-response pairs. These request-response pairs are stored as .yaml files in tests/cassettes directory.

The test/cassettes directory is organized as follows:

• Each folder per one test file.
• Each .yaml file per one test function.

For the purposes of this test suite, these request-response pairs are assumed to be all correct. In the event that WAQI API changes their specifications (unlikely), these request-response pairs need to be re-recorded. See the next section.

By default, pytest-recording will only use existing cassettes for testing, and will raise error if there's a new interaction that is not contained in existing cassettes. This prevents "accidentally" making a request that is not already been mocked.

This default behavior can be overridden by giving a record-mode argument when invoking pytest:

• pytest --record-mode=once to write new cassettes but not new request-response pairs within existing cassettes.
• pytest --record-mode=new_episodes to write new interactions, even when there's an existing cassette.
• pytest --record-mode=rewrite to rewrite all existing cassettes.
• pytest --record-mode=all to record all interactions again.
• pytest --record-mode=none(default) to only use existing cassettes and raise error if there's a new request that is not recorded in the existing cassettes.

To have more confidence that the tests will not go over the wire, the --block-network flag can also be passed to block all network access.

For more information about pytest-recording:

• pytest-recording homepage
• VCRpy documentation about record modes