[MRG] docs: Fixes #378 — restore 'Running tests locally' in CONTRIBUTING.md

[jbbqqf]

Summary

Restores a "Running the test suite locally" subsection to CONTRIBUTING.md so new contributors know how to verify their changes before opening a PR. Issue #378 reports that this guidance was lost during a previous CONTRIBUTING update.

Fixes #378 — Contributing.MD no longer contains instructions to run tests locally.

Context

The current CONTRIBUTING.md walks new contributors through forking, branching and pushing, but never tells them which command runs the tests or where the tests live. New contributors hitting the file have to grep the repo (or guess pytest) before they can validate a fix locally — exactly the friction the original issue raised.

The added section sits right before the existing Pull Request Checklist (which already says "Bug-fixes or new features should be provided with non-regression tests" but doesn't say how to run them), so the two pieces of guidance now flow together.

Changes

• CONTRIBUTING.md — added a ### Running the test suite locally subsection covering:
  • creating a venv + editable install of tslearn + pytest,
  • running the full pytest tests/ suite from the repo root,
  • running a single file / single test (pytest tests/test_metrics.py::test_dtw -v),
  • running doctests for a module (pytest --doctest-modules tslearn/metrics/dtw_variants.py),
  • a one-liner about optional extras (h5py, tensorflow, torch).

Documentation-only — no behavioural change.

Reproduce BEFORE/AFTER yourself (copy-paste)

# --- one-time setup ---
git clone https://github.com/tslearn-team/tslearn.git /tmp/repro && cd /tmp/repro

# --- BEFORE (origin/main) ---
git checkout origin/main
grep -c "pytest" CONTRIBUTING.md
# Expected: 0  (no test instructions present)

# --- AFTER (this PR) ---
git fetch https://github.com/jbbqqf/tslearn.git feat/378-contributing-tests-section
git checkout FETCH_HEAD
grep -c "pytest" CONTRIBUTING.md
# Expected: >= 4  (full pytest section, single-test example, doctest example)

What I ran locally

• pytest tests/ against the new instructions to confirm the documented commands actually run on a clean editable install. Passing locally.
• Visual diff inspection of CONTRIBUTING.md — section sits before Pull Request Checklist; existing structure preserved.

Edge cases tested

#	Scenario	Input	Expected	Verified by
1	Documentation-only diff	git diff --stat	only CONTRIBUTING.md modified	manual git diff
2	Existing content preserved	full CONTRIBUTING.md	every previous section still present, only the new subsection inserted	manual diff

Risk / blast radius

Documentation-only — zero runtime impact.

Release note

docs: CONTRIBUTING.md regained a "Running the test suite locally" section (#378).

---

PR drafted with assistance from Claude Code. The reproducer block above was used during development; it is the same one a reviewer can paste verbatim.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.70%. Comparing base (2f2029a) to head (87514fd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #672   +/-   ##
=======================================
  Coverage   93.70%   93.70%           
=======================================
  Files          73       73           
  Lines        6986     6986           
=======================================
  Hits         6546     6546           
  Misses        440      440           

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[charavelg]

Hi @jbbqqf and thanks for your PR, glad to welcome you onboard.

The documentation also includes a contributing section (docs/contributing.rst) and could benefit from the same treatment.
Furthermore, the information is currently duplicated which leads to inconsistency.

Do you think this PR can be adapted to handle both concerns?