Testing

Unit test implementation

Since this module accesses a web service, writing self contained unit tests which can be run without network access is not totally straightforward.

Unit tests for this module are implemented using vcrpy (https://vcrpy.readthedocs.io/en/latest/) and pytest-recording (https://github.com/kiwicom/pytest-recording). This works as follows:

• Tests are written to access the server as normal

• The tests are run in a mode where vcrpy records all http requests and responses to a “cassette” file

• On subsequent test runs vcrpy can generate mock http responses using the stored data

The pytest-recording plugin provides a mechanism to configure vcrpy in pytest unit tests using decorators.

Writing unit tests

Http responses are stored as gzipped messagepack for compactness. The module hdfstream.testing provides the vcrpy serializer and persister classes used to implement this.

To configure pytest to record http responses in messagepack format, this line should be included in conftest.py:

from hdfstream.testing import pytest_recording_configure, vcr_config

Then the decorator @pytest.mark.vcr can be added to unit test functions to enable recording of http responses. E.g.:

@pytest.mark.vcr
def test_dir_listing():
  import hdfstream
  root = hdfstream.open("https://localhost:8443/hdfstream", "/")
  ...

To run the unit tests in a “live” mode where real http requests are made and the responses are recorded:

pytest –record-mode=rewrite

This will create a cassettes directory with the encoded responses, overwriting any existing data. After that the unit tests can be run in offline mode with just:

pytest

In this case the stored responses will be used and no network access is required. This can be used to write tests for other modules which make use of the hdfstream module.