testing-cast

name	testing-cast
description	Guides pytest test writing for LangGraph casts with mocking patterns for LLM/API/Store calls. Use when writing tests, need mock strategies, setting up fixtures, testing nodes/graphs (v3 event streaming, timeouts, error handlers, graceful shutdown), or ask "write tests", "mock LLM", "test coverage".
version	2026.05.26
author	Proact0
allowed-tools	["Bash(uv run pytest *)","Read","Write","Edit","AskUserQuestion"]

Testing Cast Skill

Write effective pytest tests for {{ cookiecutter.act_name }} Act's casts.

When NOT to Use

• Writing implementation → developing-cast
• Designing architectures → architecting-act
• Project / cast scaffolding → run uv run act new (project) or uv run act cast (new cast) directly

Quick Reference

# Run tests
uv run pytest                              # All tests
uv run pytest tests/node_tests/            # All node tests
uv run pytest tests/cast_tests/            # All cast (graph) tests
uv run pytest -k "test_my_function"        # Match name
uv run pytest -v                           # Verbose
uv run pytest -x                           # Stop on first failure
uv run pytest --lf                         # Last failed only

# With coverage
uv run pytest --cov=casts --cov-report=html

Test Organization

The scaffold places tests at the project root under tests/, organized by scope:

{{ cookiecutter.act_slug }}/
├── casts/
│   └── {{ cookiecutter.cast_snake }}/        # cast implementation
└── tests/
    ├── conftest.py                            # shared fixtures (create as needed)
    ├── cast_tests/
    │   └── {{ cookiecutter.cast_snake }}_test.py    # graph-level tests (suffix: *_test.py)
    └── node_tests/
        └── test_node.py                       # node tests for the initial cast (prefix: test_*.py)

Location	Naming	Scope
tests/cast_tests/{cast_snake}_test.py	<cast_snake>_test.py suffix	Whole-graph invocation tests; act cast auto-creates one per cast
tests/node_tests/test_<something>.py	test_*.py prefix	Per-node behavior tests
tests/conftest.py	fixed	Shared fixtures across cast_tests/ and node_tests/

The {cast_snake}_test.py suffix naming for cast tests is what act cast generates — do not rename to test_<cast>.py.

Resources

Use when	Resource
testing sync/async nodes, drain-aware nodes	testing-nodes.md
testing graphs (invoke, routing, streaming v3, timeouts, error handlers, graceful shutdown)	testing-graphs.md
mocking LLM / API / Store calls	mocking.md
reusable fixtures (graph, mock model, mock store)	fixtures.md
coverage targeting and reporting	coverage.md

Best Practices

DO:

• Test behavior, not implementation
• Use descriptive names
• Arrange-Act-Assert pattern
• Mock external dependencies
• Test error paths

DON'T:

• Test private methods
• Order-dependent tests
• Use sleep() for timing
• Aim for 100% coverage