fix(scaffold): ship placeholder pytest file so first commit succeeds (DOT-491)

[ichoosetoaccept]

Closes DOT-491

Summary

• Add project/tests/__init__.py and project/tests/test_{{python_package_import_name}}.py.jinja — a one-line smoke test that imports the package.
• Add the placeholder test file to _skip_if_exists in copier.yml so copier update never overwrites real tests once the user has written them.
• Update unit tests: rename test_tests_directory_not_generated → test_tests_directory_has_placeholder and adjust test_app_type_no_scaffold_code to allow the placeholder.

Why

pytest-testmon exits with code 5 when no tests are collected, which broke the very first commit on every freshly scaffolded project. Shipping a single passing test gets pytest to exit 0; the user replaces it as soon as they write real tests.

Test plan

• poe test — green
• Full first-commit e2e regression coverage added in test(scaffold): add full first-commit e2e regression test #310

[linear]

DOT-491 Ship placeholder test file in scaffold — first commit fails on fresh project

[ichoosetoaccept]

This change is part of the following stack:

• fix: scaffolded files end with single trailing newline #306
  • fix(prek): keep lychee on a versioned tag after autoupdate (DOT-492) #307
    • fix(scaffold): ship placeholder pytest file so first commit succeeds (DOT-491) #308 ◀
      • fix(lychee): exclude self-referential URLs and fix stale GitHub branch-protection docs link #309
        • test(scaffold): add full first-commit e2e regression test #310

_{Change managed by git-spice.}

[greptile-apps]

Greptile Summary

This PR ships a placeholder pytest smoke test (test_{{python_package_import_name}}.py.jinja) and an empty tests/__init__.py so that pytest-testmon exits 0 (instead of code 5 for "no tests collected") on the first commit of every freshly scaffolded project. Both files are added to _skip_if_exists so copier update never overwrites real tests once the user has written them. The unit tests are updated to verify the placeholder is present for both app and lib project types.

Confidence Score: 5/5

Safe to merge — focused fix with no logic issues, correct _skip_if_exists usage, and positive test coverage for both project types.

All findings are P2 or lower. The template syntax follows the established pattern, the _skip_if_exists entries are correct, the empty __init__.py is intentional, and the updated tests verify the new behavior for both app and lib project types.

No files require special attention.

Important Files Changed

Filename	Overview
copier.yml	Adds tests/__init__.py and tests/test_{{ python_package_import_name }}.py to _skip_if_exists, following the established pattern used for src/{{ python_package_import_name }}/__init__.py.
project/tests/init.py	Empty package marker file — correct and intentional.
project/tests/test_{{python_package_import_name}}.py.jinja	New Jinja template generating a one-assertion smoke test; uses project_name and python_package_import_name correctly, no conditional blocks, renders valid Python for any valid slug.
tests/test_template.py	Renames the old "not generated" assertion to a positive placeholder check, loops over both project types, and removes the now-invalid __init__.py absence assertion from test_app_type_no_scaffold_code.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[copier copy / copier update] --> B{File exists in destination?}
    B -- No --> C[Generate tests/__init__.py\nand test_pkg.py from template]
    B -- Yes --> D[Skip — _skip_if_exists\npreserves user's real tests]
    C --> E[First commit:\npytest-testmon collects test → exit 0 ✓]
    D --> F[copier update safe:\nuser's tests untouched]

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