=============================== The Hypothesis example database =============================== When Hypothesis finds a bug it stores enough information in its database to reproduce it. This enables you to have a classic testing workflow of find a bug, fix a bug, and be confident that this is actually doing the right thing because Hypothesis will start by retrying the examples that broke things last time. ----------- Limitations ----------- The database is best thought of as a cache that you never need to invalidate: Information may be lost when you upgrade a Hypothesis version or change your test, so you shouldn't rely on it for correctness - if there's an example you want to ensure occurs each time then :ref:`there's a feature for including them in your source code ` - but it helps the development workflow considerably by making sure that the examples you've just found are reproduced. The database also records examples that exercise less-used parts of your code, so the database may update even when no failing examples were found. -------------------------------------------- Upgrading Hypothesis and changing your tests -------------------------------------------- The design of the Hypothesis database is such that you can put arbitrary data in the database and not get wrong behaviour. When you upgrade Hypothesis, old data *might* be invalidated, but this should happen transparently. It can never be the case that e.g. changing the strategy that generates an argument gives you data from the old strategy. ------------------------------- ExampleDatabase implementations ------------------------------- Hypothesis' default :obj:`~hypothesis.settings.database` setting creates a :class:`~hypothesis.database.DirectoryBasedExampleDatabase` in your current working directory, under ``.hypothesis/examples``. If this location is unusable, e.g. because you do not have read or write permissions, Hypothesis will emit a warning and fall back to an :class:`~hypothesis.database.InMemoryExampleDatabase`. Hypothesis provides the following :class:`~hypothesis.database.ExampleDatabase` implementations: .. autoclass:: hypothesis.database.InMemoryExampleDatabase .. autoclass:: hypothesis.database.DirectoryBasedExampleDatabase .. autoclass:: hypothesis.database.ReadOnlyDatabase .. autoclass:: hypothesis.database.MultiplexedDatabase .. autoclass:: hypothesis.extra.redis.RedisExampleDatabase --------------------------------- Defining your own ExampleDatabase --------------------------------- You can define your :class:`~hypothesis.database.ExampleDatabase`, for example to use a shared datastore, with just a few methods: .. autoclass:: hypothesis.database.ExampleDatabase :members: