Hypothesis

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:func:`~hypothesis.strategies.randoms` no longer produces ``1.0``, matching
the exclusive upper bound of :obj:`random.Random.random` (:issue:`4297`).

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This release adds a ``"hypothesis-urandom"`` :ref:`backend <alternative-backends>`, which draws randomness from ``/dev/urandom`` instead of Python's PRNG. This is useful for users of `Antithesis <https://antithesis.com/>`_ who also have Hypothesis tests, allowing Antithesis mutation of ``/dev/urandom`` to drive Hypothesis generation. We expect it to be strictly slower than the default backend for everyone else.

It can be enabled with ``settings(backend="hypothesis-urandom")``.

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For strategies which draw make recursive draws, including :func:`~hypothesis.strategies.recursive` and :func:`~hypothesis.strategies.deferred`, we now generate examples with duplicated subtrees more often. This tends to uncover interesting behavior in tests.

For instance, we might now generate a tree like this more often (though the details depend on the strategy):

.. code-block:: none

┌─────┐
┌──────┤ a ├──────┐
│ └─────┘ │
┌──┴──┐ ┌──┴──┐
│ b │ │ a │
└──┬──┘ └──┬──┘
┌────┴────┐ ┌────┴────┐
┌──┴──┐ ┌──┴──┐ ┌──┴──┐ ┌──┴──┐
│ c │ │ d │ │ b │ │ ... │
└─────┘ └─────┘ └──┬──┘ └─────┘
┌────┴────┐
┌──┴──┐ ┌──┴──┐
│ c │ │ d │
└─────┘ └─────┘

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Improves input validation for several strategies in our :ref:`pandas extra
<hypothesis-pandas>`, so that they raise a helpful ``InvalidArgument`` rather
than ``OverflowError``.

Discovered by our recent :ref:`string generation upgrade <v6.128.0>`.

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Rename a few internal classes for clarity.

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:func:`~hypothesis.strategies.text` now occasionally generates from a preselected list of strings which are likely to find bugs. These include ligatures, right-to-left and top-to-bottom text, emojis, emoji modifiers, strings like ``"Infinity"``, ``"None"``, and ``"FALSE"``, and other interesting things. This is especially useful when testing the full unicode range, where the search space is too large for uniform sampling to be very effective.

Of course, examples generated this way shrink just like they normally would. It was always possible for Hypothesis to generate these strings; it is just more likely after this change. From the outside, it is as if Hypothesis generated the example completely randomly.

Many thanks to the `Big List of Naughty Strings <https://github.com/minimaxir/big-list-of-naughty-strings>`_, `Text Rendering Hates You <https://faultlore.com/blah/text-hates-you/>`_, and `Text Editing Hates You Too <https://lord.io/text-editing-hates-you-too/>`_ for forming the basis of this list.