feat: testing function

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

docs/plugins.md

@@ -53,6 +53,20 @@ You have `processed.results` and `processed.families` from the return of
 {func}`~repo_review.processor.collect_all` to get `.fixtures`, `.checks`, and
 `.families`.
 
+### Unit testing
+
+You can also run unit tests with the {func}`~repo_review.testing.compute_check` helper. It is used like this:
+
+```python
+def test_has_tool_ruff_unit() -> None:
+    assert repo_review.testing.compute_check("RF001", ruff={}).result
+    assert not repo_review.testing.compute_check("RF001", ruff=None).result
+```
+
+It takes the check name and any fixtures as keyword arguments. It returns a
+{class}`~repo_review.checks.Check` instance, so you can see if the `.result` is
+`True`/`False`/`None`, or check any of the other properties.
+
 ## An existing package
 
 Since writing a plugin does not require depending on repo-review, you can also

src/repo_review/checks.py

@@ -120,3 +120,26 @@ def get_check_description(name: str, check: Check) -> str:
     .. versionadded:: 0.8
     """
     return (check.__doc__ or "").format(self=check, name=name)
+
+
+def process_result_bool(
+    result: str | bool | None, check: Check, name: str
+) -> str | None:
+    """
+    This converts a bool into a string given a check and name. If the result is a string
+    or None, it is returned as is.
+
+    :param result: The result to process.
+    :param check: The check instance.
+    :param name: The name of the check.
+    :return: The final string or None.
+
+    .. versionadded:: 0.11
+    """
+    if isinstance(result, bool):
+        return (
+            ""
+            if result
+            else (check.check.__doc__ or "Check failed").format(name=name, self=check)
+        )
+    return result

src/repo_review/processor.py

@@ -10,7 +10,13 @@
 import markdown_it
 
 from ._compat.importlib.resources.abc import Traversable
-from .checks import Check, collect_checks, get_check_url, is_allowed
+from .checks import (
+    Check,
+    collect_checks,
+    get_check_url,
+    is_allowed,
+    process_result_bool,
+)
 from .families import Family, collect_families
 from .fixtures import apply_fixtures, collect_fixtures, compute_fixtures, pyproject
 from .ghpath import EmptyTraversable
@@ -211,16 +217,7 @@ def process(
     for name in ts.static_order():
         if all(completed.get(n, "") == "" for n in graph[name]):
             result = apply_fixtures({"name": name, **fixtures}, tasks[name].check)
-            if isinstance(result, bool):
-                completed[name] = (
-                    ""
-                    if result
-                    else (tasks[name].check.__doc__ or "Check failed").format(
-                        name=name, self=tasks[name]
-                    )
-                )
-            else:
-                completed[name] = result
+            completed[name] = process_result_bool(result, tasks[name], name)
         else:
             completed[name] = None
 

src/repo_review/testing.py

@@ -0,0 +1,51 @@
+"""
+Helpers for testing repo-review plugins.
+"""
+
+from __future__ import annotations
+
+import importlib.metadata
+import textwrap
+from typing import Any
+
+from .checks import Check, get_check_url, process_result_bool
+from .fixtures import apply_fixtures
+from .processor import Result
+
+
+def compute_check(name: str, /, **fixtures: Any) -> Result:
+    """
+    A helper function to compute a check given fixtures, intended for testing.
+    Currently, all fixtures are required to be passed in as keyword arguments,
+    transiative fixtures are not supported.
+
+    :param name: The name of the check to compute.
+    :param fixtures: The fixtures to use when computing the check.
+    :return: The computed result.
+
+    .. versionadded:: 0.11
+    """
+
+    check_functions = (
+        ep.load() for ep in importlib.metadata.entry_points(group="repo_review.checks")
+    )
+    checks = {
+        k: v
+        for func in check_functions
+        for k, v in apply_fixtures(fixtures, func).items()
+    }
+    check: Check = checks[name]
+    completed_raw = apply_fixtures({"name": name, **fixtures}, check.check)
+    completed = process_result_bool(completed_raw, check, name)
+    result = None if completed is None else not completed
+    doc = check.__doc__ or ""
+    err_msg = completed or ""
+
+    return Result(
+        family=check.family,
+        name=name,
+        description=doc.format(self=check, name=name).strip(),
+        result=result,
+        err_msg=textwrap.dedent(err_msg),
+        url=get_check_url(name, check),
+    )

tests/test_package.py

@@ -6,6 +6,7 @@
 import pytest
 
 import repo_review as m
+import repo_review.testing
 from repo_review.processor import process
 
 DIR = Path(__file__).parent.resolve()
@@ -43,3 +44,10 @@ def test_broken_validate_pyproject(tmp_path: Path) -> None:
     (result,) = (r for r in results.results if r.name == "VPP001")
     assert "must match pattern" in result.err_msg
     assert not result.result
+
+
+def test_testing_function():
+    pytest.importorskip("sp_repo_review")
+
+    assert repo_review.testing.compute_check("RF001", ruff={}).result
+    assert not repo_review.testing.compute_check("RF001", ruff=None).result