hypothesis-testing

Hypothesis Property-Based Testing

Hypothesis is a powerful property-based testing library that automatically generates test cases to find edge cases and validate properties of your code.

Core Concept

Traditional example-based testing:

def test_addition():
    assert add(2, 3) == 5
    assert add(0, 0) == 0
    assert add(-1, 1) == 0

Property-based testing with Hypothesis:

from hypothesis import given
import hypothesis.strategies as st

@given(st.integers(), st.integers())
def test_addition_commutative(a, b):
    """Addition is commutative for ALL integers."""
    assert add(a, b) == add(b, a)

Hypothesis generates hundreds of test cases automatically, including edge cases you might not think of.

Installation

# Install hypothesis with pytest integration
uv add --dev hypothesis pytest

# Optional plugins
uv add --dev hypothesis[numpy]      # NumPy strategies
uv add --dev hypothesis[pandas]     # Pandas strategies
uv add --dev hypothesis[django]     # Django model strategies

Configuration

pyproject.toml Configuration

[tool.pytest.ini_options]
# Hypothesis settings
addopts = [
    "--hypothesis-show-statistics",  # Show test statistics
    "--hypothesis-seed=0",            # Reproducible tests (optional)
]

[tool.hypothesis]
# Maximum number of examples to generate
max_examples = 200  # Default: 100, CI: 200+

# Deadline for each test case (milliseconds)
deadline = 1000  # Default: 200ms, None to disable

# Verbosity level (quiet, normal, verbose, debug)
verbosity = "normal"

# Fail fast on first error
derandomize = false  # Set to true for deterministic tests

# Database for example storage
database = ".hypothesis/examples"  # Store found failures

# Profile-specific settings
[tool.hypothesis.profiles.dev]
max_examples = 50
deadline = 1000
verbosity = "normal"

[tool.hypothesis.profiles.ci]
max_examples = 500
deadline = 5000
verbosity = "verbose"

[tool.hypothesis.profiles.debug]
max_examples = 10
deadline = null
verbosity = "debug"