🔧 Template: Add basic tests

Add a minimal `tests` folder with a small test that relies on a simple fixture defined
in the `conftest.py`.

Since a user of the template package typically doesn't want to keep these files when
updating their template, we exclude the `tests` directory when the `update` operation
is used.

We also set two Ruff codes to ignore when linting the package for the modules in the
`tests` directory:

* `INP001`/`implicit-namespace-package`: We don't need `__init__.py` files in the tests.
* `S101`/`assert`: Assert statements are fine in tests.

Author: mbercx

copier.yml

@@ -27,3 +27,5 @@ doc_deploy:
 _subdirectory: template
 _message_after_copy: |
   The `{{package_name}}` package has been created successfully!
+_exclude:
+    - "{% if _copier_operation == 'update' -%}tests{% endif %}"

template/docs/developer.md.jinja

@@ -34,7 +34,7 @@ Or run them via:
 
     hatch run precommit:install
 
-From the extensive [Ruff ruleset](https://docs.astral.sh/ruff/rules/) that Hatch uses, we ignore the following:
+From the extensive [Ruff ruleset](https://docs.astral.sh/ruff/rules/) that Hatch uses, we ignore the following globally:
 
 | Code      | Rule                                                                                                                      | Rationale / Note                                                                                                                    |
 | --------- | ------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
@@ -44,3 +44,10 @@ From the extensive [Ruff ruleset](https://docs.astral.sh/ruff/rules/) that Hatch
 | `PLR2004` | [magic-value-comparison](https://docs.astral.sh/ruff/rules/magic-value-comparison/)                                       | We have a lot of “magic values” to compare with in scientific code; naming them all would reduce readability for little benefit.    |
 | `FBT002`  | [boolean-default-value-positional-argument](https://docs.astral.sh/ruff/rules/boolean-default-value-positional-argument/) | We understand the concept, but adhering to this rule is not a small change in syntax; disable for now.                              |
 | `TID252`  | [relative-imports](https://docs.astral.sh/ruff/rules/relative-imports/)                                                   | We don’t mind relative imports; as long as you don’t go up a level, they’re more readable (less verbose).                           |
+
+And the following rules for the files in the `tests` directory:
+
+| Code      | Rule                                                                                                                      | Rationale / Note                                                                                                                    |
+| --------- | ------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
+| `INP001`  | [implicit-namespace-package](https://docs.astral.sh/ruff/rules/implicit-namespace-package/)                               | When tests are not part of the package, there is no need for `__init__.py` files.                                                   |
+| `S101`    | [assert](https://docs.astral.sh/ruff/rules/assert/)                                                                       | Asserts should not be used in production environments, but are fine for tests.                                                      |

template/pyproject.toml.jinja

@@ -58,3 +58,5 @@ lint.ignore = [
     "FBT002",  # https://docs.astral.sh/ruff/rules/boolean-default-value-positional-argument/
     "TID252",  # https://docs.astral.sh/ruff/rules/relative-imports/
 ]
+[tool.ruff.lint.per-file-ignores]
+"tests/**/*.py" = ["INP001", "S101"]

template/tests/conftest.py

@@ -0,0 +1,10 @@
+"""Project-wide pytest fixtures & hooks.
+
+Docs: https://docs.pytest.org/en/stable/how-to/fixtures.html#conftest-py-sharing-fixtures-across-multiple-files
+"""
+import pytest
+
+
+@pytest.fixture
+def readability_counts() -> bool:
+    return True

template/tests/test_example.py

@@ -0,0 +1,3 @@
+
+def test_example(readability_counts):
+    assert readability_counts is True