Add pytest suite and CI for Python unit tests

[Manik-Khajuria-5]

Description

Wires up pytest as a first-class, config-driven test runner for the Python side

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Motivation and Context

The repo had no operational Python test setup no pytest config, pytest was not a declared dependency, and no CI ran Python tests (docs even stated "no Python unit tests"). This adds a proper, CI-gated unit-test layer alongside the existing
Cypress E2E/visual tests so backend logic is covered on every PR.

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How Has This Been Tested?

Work in Progress

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Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• I adapted the version number under py/visdom/VERSION accord
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

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[Manik-Khajuria-5]

@rajnisht7 @vedansh-5 @Jayantparashar10 @tonypzy Please review this PR

[tonypzy]

except that, lgtm

[Manik-Khajuria-5]

@tonypzy I have changed the version Can u please review this PR again

[Manik-Khajuria-5]

@tonypzy PLease review this PR

[Copilot]

Pull request overview

This PR introduces a first-class pytest-based Python unit testing layer for Visdom (config + initial smoke test) and wires it into GitHub Actions, alongside updates to contributor/testing documentation.

Changes:

• Add pytest/pytest-cov to Python test dependencies and introduce a root pyproject.toml pytest configuration scoped to py/tests/.
• Add an initial Python smoke test to validate test discovery and import visdom.
• Add a new GitHub Actions workflow to run pytest on PRs/pushes, and update docs to reflect the new Python testing setup.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test-requirements.txt	Adds pytest tooling dependencies for the new Python test suite.
pyproject.toml	Adds pytest discovery/configuration (scoped testpaths, pythonpath, markers).
py/tests/test_smoke.py	Introduces initial smoke tests for pytest discovery and package import.
.github/workflows/python-tests.yml	Adds CI job to run pytest on PRs and branch pushes.
AGENTS.md	Updates contributor testing and PR checklist guidance to include pytest.
.agents/context/testing.md	Updates internal agent/testing guidance to include pytest usage and CI info.
REFACTORING.md	Updates verification plan instructions to use the new pytest configuration.