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Generate test data from JSON schemata with Hypothesis

Project description


A Hypothesis strategy for generating data that matches some JSON schema. It is currently in early alpha, but you can use it if you want. Here's the PyPI page.

The public API consists of a just two functions:


Takes a JSON schema and return a strategy for allowed JSON objects.

This strategy supports almost all of the schema elements described in the draft RFC as of February 2019 (draft07), with the following exceptions:

  • For objects, the "dependencies" keyword is not supported.
  • Subschemata are not supported, i.e. the "if", "then", and "else" keywords, and the "allOf, "anyOf", "oneOf", and "not" keywords.
  • Schema reuse with "definitions" is not supported.
  • string-encoding of non-JSON data is not supported.
  • schema annotations, i.e. "title", "description", "default", "readOnly", "writeOnly", and "examples" are not supported.
  • JSON pointers are not supported.

Draft07 support depends on having a compatible version of jsonschema, which at time of writing is limited to the pre-release 3.0.0x versions. Draft04 remains fully supported with the same exceptions.


A Hypothesis strategy for arbitrary JSON schemata.

This strategy may generate anything that can be handled by from_schema, and is used to provide full branch coverage when testing this package.

Supported versions

hypothesis-jsonschema does not support Python 2, because it's close to end of life and Python 3.6+ is a much nicer language. Contact me if you would like this changed and are willing to either pay for or do the work to support Python 2.

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.


0.5.0 - 2019-02-22

  • Works with jsonschema 3.0 pre-release
  • Initial support for draft06 and draft07

0.4.2 - 2019-02-14

  • Dropped dependency on canonicaljson
  • Less warnings on Python 3.7

0.4.1 - 2019-02-06

  • Relicensed under the more permissive Mozilla Public License, like Hypothesis
  • Requires Hypothesis version 4.0 or later
  • Fixed an array bounds bug with maxItems and contains keywords

0.4.0 - 2018-11-25

Supports string formats (email, datetime, etc) and simple use of the "contains" keyword for arrays.

0.3.0 - 2018-11-25

Good support for all basic types. MVP.

0.2.0 - 2018-11-24

Inference for null, boolean, string, and numeric types.

0.1.0 - 2018-11-21

Stake in the ground (generate arbitrary JSON and filter it!)

Project details

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