openflexure-microscope-server/hardware-specific-tests/README.md

Hardware specific tests

This directory contains unit tests that require specific hardware to run. Current they implement tests for code that interacts with the Raspberry Pi Camera.

Hardware specific tests for the Pi Camera.

The OpenFlexure Microscope Server runs automated test in the cloud (via the GitLab CI) to test each version of the code as changes are proposed and merged. As these tests run in the cloud they do not have access to actual microscope hardware. As such, these tests either test specific blocks of code that don't need hardware access or make use of simulated hardware via the simulation camera and dummy stage.

To test the code that interacts with the hardware itself, hardware specific tests are needed and they must be run with the hardware available. This directory provides these tests. For now the only hardware specific tests are for the Pi Camera. They must be run on a Raspberry Pi with a Pi Camera attached.

In GitLab we track our "code coverage", this tells us which lines of code have been executed during testing. The picamera_tests.py script in the root of the repository can be used to report the coverage from these tests. See the section below on "Reporting the coverage to GitLab".

Running and reporting the test coverage to GitLab (for merge requests)

It is essential to stop the server before running these tests:

ofm stop

To create a coverage report that will be included into the repository (and reported to GitLab) run:

./picamera_tests.py run

This will first run pytest on the hardware specific tests. This creates a .coverage database that can be used to analyse the code coverage of these tests. This will be copied to .coverage.picamera. The script will then create a zip of these test results along with hashes of source code for the Pi Camera:

• picamera.py
• picamera_recalibrate_utils.py
• __init__.py in the camera directory that defines BaseCamera

This zip should then be committed to the repository.

Running these tests during development

As before, the server must be stopped before running these tests.

The camera test are very slow as they run on hardware. They can be run with:

pytest hardware-specific-tests

However, this will not archive the tests in the Git repository for reporting the coverage. For this, see the section above on reporting the coverage.

When writing and debugging these unit tests, it is often best to run a specific test and to use the -s flag to see the print statements. It is also often useful to use --pdb to drop you into a python debug session on any failure. For example, you might run:

pytest hardware-specific-tests/picamera2/test_exposure_time_drift.py::test_exposure_time_saves_and_loads -s --pdb

CI explanation

When the CI runs on GitLab to calculate code coverage, it will first run the tests in the tests directory in one job, and archive this as .coverage.main. Then it will run a second job that:

• Imports the archive of .coverage.main for the tests just run on the server
• Unzip the zip of the results of running tests on the Pi Camera (.coverage.picamera)
• Check that the hashes for the Pi Camera source code have not changed. If they have changed it will error and ask for the picamera tests to be re-run on a Raspberry Pi.
• Runs coverage combine to create a single .coverage report that combines the coverage from both .coverage.main and .coverage.picamera.
• Generates the information needed to display the coverage in GitLab

This ensures that:

• Hardware specific tests are re-run if the relevant source code changes.
• The coverage for hardware specific tests is reported correctly
• The hardware specific tests do not need re-running when other code that does not affect PiCamera interaction is updated.

Creating a combined report locally

To create a combined coverage report locally (similar to the one created on CI) first run all normal tests with pytest.

Copy the .coverage file to .coverage.main

cp .coverage .coverage.main

Then run:

./picamera_tests.py unzip

to get the .coverage.picamera file.

To combine reports run:

coverage combine

It is then possible to run:

• coverage report to get the in-terminal report of the coverage.
• coverage html to get the HTML overview of covered lines.
• coverage xml to get an XML report any software that may need it.