hypothesis-jsonschema

A Hypothesis strategy for generating data that matches some JSON schema.

Here's the PyPI page.

API

The public API consists of just one function: hypothesis_jsonschema.from_schema, which takes a JSON schema and returns a strategy for allowed JSON objects.

from hypothesis import given

from hypothesis_jsonschema import from_schema


@given(from_schema({"type": "integer", "minimum": 1, "exclusiveMaximum": 10}))
def test_integers(value):
    assert isinstance(value, int)
    assert 1 <= value < 10


@given(
    from_schema(
        {"type": "string", "format": "card"},
        # Standard formats work out of the box.  Custom formats are ignored
        # by default, but you can pass custom strategies for them - e.g.
        custom_formats={"card": st.sampled_from(EXAMPLE_CARD_NUMBERS)},
    )
)
def test_card_numbers(value):
    assert isinstance(value, str)
    assert re.match(r"^\d{4} \d{4} \d{4} \d{4}$", value)


@given(from_schema({}, allow_x00=False, codec="utf-8").map(json.dumps))
def test_card_numbers(payload):
    assert isinstance(payload, str)
    assert "\0" not in payload  # use allow_x00=False to exclude null characters
    # If you want to restrict generated strings characters which are valid in
    # a specific character encoding, you can do that with the `codec=` argument.
    payload.encode(codec="utf-8")

For more details on property-based testing and how to use or customise strategies, see the Hypothesis docs.

JSONSchema drafts 04, 05, and 07 are fully tested and working. As of version 0.11, this includes resolving non-recursive references!

Supported versions

hypothesis-jsonschema requires Python 3.11 or later. In general, 0.x versions will require very recent versions of all dependencies because I don't want to deal with compatibility workarounds.

hypothesis-jsonschema may make backwards-incompatible changes at any time before version 1.x - that's what semver means! - but I've kept the API surface small enough that this should be avoidable. The main source of breaks will be if or when schema that never really worked turn into explicit errors instead of generating values that don't quite match.

You can sponsor me to get priority support, roadmap input, and prioritized feature development.

Contributing to hypothesis-jsonschema

We love external contributions - and try to make them both easy and fun. You can read more details in our contributing guide, and see everyone who has contributed on GitHub. Thanks, everyone!

Changelog

Patch notes can be found in CHANGELOG.md.

Security contact information

To report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure.