Introduction¶

StepUp Core supports domain-specific build features through extension packages that live outside the core. An extension is a regular Python package that implements the desired features and registers them with StepUp Core, optionally reusing the shared stepup namespace. Two such extensions exist today:

This section explains how to write your own extension. A package can implement three types of components:

Custom API functions that send new steps (and other information) to the StepUp director process.
Console scripts, e.g. wrappers of external tools, intended to run as a step in a workflow.
Custom tools, which appear as new subcommands in the StepUp CLI.

Testing an Extension¶

The module stepup.core.pytest holds test utilities that extensions can reuse:

run_example() runs an integration example in a temporary directory and compares the files it produces to the expected ones in the source directory. run_plan() runs the plan.py of an example as an ordinary Python script.
ConventionTests collects the tests for the coding conventions of the StepUp packages, most importantly that every module declares __all__ and that no module imports a name another module does not export. Subclass it in a test module and name the package to be tested:
```
from stepup.core.pytest import ConventionTests


class TestConventions(ConventionTests):
    package = "stepup.spam"
```
Set example_rc = None in the subclass when the test suite has no integration examples. For the failing assertions to explain themselves, add the following line to conftest.py:
```
pytest.register_assert_rewrite("stepup.core.pytest")
```