docs: describe the Python test suite

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -28,43 +28,45 @@ When behaviour of the image changes (Features, Bugfixes, Changes in the API) ple
 
 ## Tests
 
-The test suites build the image and exercise it as a real container. They need
-`bash` and `docker`, nothing else:
+The tests build the image and exercise it as a real container. Tools are pinned
+in `mise.toml` (Python, [uv](https://docs.astral.sh/uv/),
+[Task](https://taskfile.dev/), container-structure-test), Python dependencies in
+`uv.lock`. You need [mise](https://mise.jdx.dev/) and Docker, nothing else:
 
 ```sh
-bash test/run.sh                 # build the image and run every suite
-bash test/run.sh --no-build      # reuse an already built image
-bash test/run.sh --suite compat  # run a single suite
+mise install          # install the pinned tools
+task test             # build the image and run every suite
+task test:sabotage    # self test, see below
+task lint             # ruff check and format check of tests/
 ```
 
-They run unchanged on Linux, macOS and Windows/Git-Bash. On Git-Bash the
-scripts set `MSYS_NO_PATHCONV=1` and `MSYS2_ARG_CONV_EXCL='*'` themselves,
-because MSYS would otherwise rewrite container paths such as
-`/usr/bin/backup` into `C:/Program Files/Git/usr/bin/backup` before `docker`
-sees them. Nothing has to be exported by hand.
+Single suites: `task test:structure`, `task test:compat`, `task test:features`.
+Arguments after `--` go to pytest, e.g. `task test:compat -- -k hooks`. Set
+`IMAGE` to test an already built image instead of `restic-backup-docker:test`.
 
-There are three suites:
+The suites live in `tests/`:
 
-* **compat** (`test/compat.sh`) - backup, restore, forget, check, hooks and
+* **compat** (`tests/test_compat.py`) - backup, restore, forget, check, hooks and
   failure handling against the default configuration. These tests describe the
   behaviour users rely on. A change that turns one of them red is a breaking
   change.
-* **features** (`test/features.sh`) - tests for optional features. Each block
-  is guarded by a detection check against the built image, so a feature that is
-  not part of the image is reported as `SKIP` instead of failing. Pull requests
-  that add such a feature are therefore covered as soon as they are rebased,
-  without the author having to write the basic tests. After merging a feature,
-  add its gate name to `test/required-features.txt` so that a missing feature
-  turns into a failure.
-* **structure** (`test/structure.yml`) - image layout checks via
+* **features** (`tests/test_features.py`) - tests for optional features. Each
+  test is marked `@pytest.mark.feature("<gate>")` and guarded by a detection
+  check against the built image, so a feature that is not part of the image is
+  reported as skipped instead of failing. Pull requests that add such a feature
+  are therefore covered as soon as they are rebased, without the author having
+  to write the basic tests. After merging a feature, add its gate name to
+  `tests/required-features.txt` so that a missing feature turns into a failure.
+* **structure** (`tests/structure.yml`) - image layout checks via
   [container-structure-test](https://github.com/GoogleContainerTools/container-structure-test).
-  When the tool is not installed, its official container image is used instead.
+  `tests/structure.py` runs it and removes the containers and anonymous volumes
+  it leaves behind.
 
-`bash test/run.sh --sabotage` is a self test: it breaks the backup call on a
-throwaway copy of the tree and expects the compat suite to fail. CI runs it so
-that the suites cannot be watered down into always passing.
+`task test:sabotage` is a self test: it breaks the backup call on a throwaway
+copy of the tree and expects the compat tests to fail. CI runs it so that the
+tests cannot be watered down into always passing.
 
-When you add a feature, please add a block to `test/features.sh` for it.
+When you add a feature, please add tests with a `feature` marker for it.
 
 ## Hooks