hypothesis-jsonschema

What it is and what it does

hypothesis-jsonschema bridges Hypothesis (a property-based testing framework) and JSON Schema by converting a schema into a Hypothesis strategy that generates valid JSON data matching that schema. Rather than hand-writing test inputs, you define a schema and the package generates diverse, valid examples automatically—useful for testing APIs, data pipelines, or any code that consumes JSON.

The package exposes a single public function, `from_schema()`, which takes a JSON schema and optional configuration (custom format handlers, encoding constraints) and returns a strategy for Hypothesis's `@given` decorator. It supports JSON Schema drafts 04, 05, and 07, handles non-recursive schema references, and allows you to customize how custom formats are generated. Dependencies are minimal: only hypothesis and jsonschema.

Use it for:

• Test REST API endpoints by generating valid JSON payloads that match your OpenAPI or JSON Schema specification.
• Fuzz data validation logic by creating diverse inputs that conform to a schema but exercise edge cases.
• Verify data transformation pipelines by generating schema-compliant input and checking output correctness.
• Build schema-driven test suites where test data is derived automatically from your schema rather than hardcoded.
• Validate custom format handlers by generating data with specific string formats (e.g., email, UUID, card numbers).

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Generates random JSON data that conforms to a given JSON schema, for use as test input in property-based testing with Hypothesis.

Yes, if you use Hypothesis for property-based testing and need to generate JSON data. The package is stable, has no known vulnerabilities, and low install friction. The aging maintenance status (no release in 898 days) is a minor concern for new features but not a blocker for current use—the API is small and the underlying dependencies are mature. Suitable for production test suites.

Install

hypothesis-jsonschema on PyPI

pip install hypothesis-jsonschema

uv add hypothesis-jsonschema

poetry add hypothesis-jsonschema

Installing hypothesis-jsonschema

Before you install

Low friction: pure Python wheel with only two runtime dependencies (hypothesis and jsonschema). Maintenance status is aging—last release was 898 days ago, though the repository remains active with a recent commit on 2025-12-05.

License in practice

Licensed under MPL 2.0 (copyleft). You must disclose source modifications and can use it in proprietary code, but derivative works of the library itself must remain open-source under the same license.

Quickstart

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

Requires Python 3.8 or later. Hypothesis must be installed and configured for your test runner.

Verify before relying

• Whether the package still actively maintains support for JSON Schema drafts beyond 07, or if newer drafts require manual updates.
• Current compatibility with the latest versions of hypothesis and jsonschema, given the 898-day gap since last release.

Package facts

Evidence: hypothesis_jsonschema-0.23.1-py3-none-any.whl

Keywords: python, testing, fuzzing, property-based-testing, json-schema

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