## 0.10.1
### New Features
- Added `RngAlgorithm::Recorder` and supporting APIs which allow capturing
random data generated as part of generating a value or running a test.
## 0.10.0
### Breaking Changes
- The version of the `rand` crate has been increased to 0.7.
- The `proptest!` macro no longer accepts function bodies which implicitly
return a value (which would then be discarded).
- The `TupleUnion` implementation in `proptest` 0.9 has been removed and
replaced with `LazyTupleUnion`. `prop_oneof!` is unaffected and continues
to be the recommended way to build a union of strategies.
### New Features
- Enabling the `hardware-rng` optional depndency (disabled by default) allows
obtaining non-deterministic random seeds even in `no_std` environments
provided the architecture is x86 or AMD64.
- Added missing `?Sized` bound to `B` on the implementation of
`Arbitrary` for `std::borrow::Cow<'_, B>`.
### Bug Fixes
- `prop_assert!` and `prop_assume!` should now be usable in `no_std`
environments.
### Other Notes
- `rusty_fork` has been bumped to 0.3.0, which adds support for a number of
[new test flags](https://github.com/AltSysrq/rusty-fork/blob/master/CHANGELOG.md#improvements)
when running forked tests.
- The `PassThrough` RNG algorithm now returns 0 instead of panicking when it
runs out of entropy.
## 0.9.6
### Bug Fixes
- Fixed [#186](https://github.com/AltSysrq/proptest/issues/186),
a Rust future-compatibility issue.
## 0.9.5
### Bug Fixes
- Fixed a Rust future-compatibility issue (https://github.com/rust-lang/rust/pull/65819).
### New Additions
## 0.9.4
### Bug Fixes
- The `unstable` feature one again works against the latest nightly.
### Performance Improvements
- Unions and the `prop_oneof!` combinator now generate value trees
lazily.
In previous versions of `proptest`, if a value tree for a
union variant was generated, so would value trees for earlier
variants -- as a result, union value tree generation was linear in the
number of variants.
In `proptest` 0.9.4 and above, value trees are only generated for
union variants that are picked. Union value tree generation is now
independent of the number of variants.
### Deprecations
- `TupleUnion` has been deprecated, and its implementation will be
replaced by `LazyTupleUnion`'s in 0.10.0.
### Other Notes
- The return type of `prop_oneof!` has changed from `TupleUnion` to
`LazyTupleUnion`. `prop_oneof!`'s return type is documented to not be
stable, and that continues to be the case.
- Shrinking is now limited to four times as many iterations as configured
number of test cases by default.
- `prop_assert_eq!` and `prop_assert_ne!` produce output more similar to the
`assert_eq!` and `assert_ne!` macros. This should also make it easier to
visually parse out the source location in the resulting messages.
## 0.9.3
This is a minor release to correct some packaging errors. The licence files are
now included in the files published to crates.io, and some unneeded files are
now excluded.
## 0.9.2
### New Additions
- Closures generated by `prop_compose!` are now `move`. This is not expected to
cause any breakage since there is no way to successfully use a borrowing
closure with that macro.
- There is now **highly experimental** support for building on Web Assembly.
Refer to [the Proptest
book](https://altsysrq.github.io/proptest-book/proptest/wasm.html) for build
instructions.
### Other Notes
- Using proptest with the default `std` feature enabled, the `spin` crate is no
longer brought in as a dependency.
- Using proptest with the `std` feature disabled, neither `spin` nor
`lazy_static` are brought in as dependencies.
## 0.9.1
### New RNG Algorithm
Starting in this version, the default RNG algorithm has been changed from
XorShift to ChaCha since it produces higher-quality randomness. This may make
test case generation a bit slower but it avoids certain pathological cases that
the old generator had.
The old algorithm is still supported, and is used automatically when reading
old failure persistence files.
Note that this change also affects the internal representation of RNG seeds,
which affects the `FailurePersistence` trait which previously only supported
the seed representation for XorShift. This release maintains source
compatibility with 0.9.0 by providing defaults for the new methods which
delegate (when possible) to the old ones, but be aware that custom failure
persistence implementations using the old API will not function when using an
RNG other than XorShift.
To keep using the old algorithm, you can set the environment variable
`PROPTEST_RNG_ALGORITHM` to `xs` or set `Config.rng_algorithm` to
`RngAlgorithm::XorShift` in code.
Besides ChaCha, this version also adds a `PassThrough` RNG "algorithm" which
makes it possible to use an external source of entropy with Proptest.
### New Additions
- `TestRng` instances can be created with the `from_seed` function.
- `TestRunner` instances can be created with user-provided `TestRng`s.
- `TestRunner` now has a `deterministic()` constructor which uses the same RNG
every time, to facilitate doing statistical tests on strategy outputs.
- There is now a work-around for a [compiler
bug](https://github.com/rust-lang/rust/issues/52478) which prevents building
with `-C link-dead-code`. Please see this issue for details:
https://github.com/AltSysrq/proptest/issues/124
### Deprecations
- The `load_persisted_failures` and `save_persisted_failure` methods on the
`FailurePersistence` trait have been deprecated and will be removed in
0.10.0.
## 0.9.0
### Breaking Changes
- The minimum Rust version has been increased to 1.32.0.
- The version of the `rand` crate has been increased to 0.6.
- The `ValueFor` type alias (deprecated in 0.8.0) has been removed. Replace
`ValueFor<S>` with `S::Value` or `<S as Strategy>::Value` as necessary.
- `From<SizeRange>` implementations converting a `SizeRange` back to various
std types have been removed since they were of limited utility and had
unclear or incorrect conversion properties.
- Many optional elements (such as trailing commas or function visibility
modifiers) in certain macros could be specified more than once. The macros
now accept at most one occurrence.
- Visibility modifiers inside `prop_compose` must no longer be enclosed in
brackets. Unless other modifiers (e.g., `unsafe`) are also in use, simply
removing the brackets is sufficient.
### New Additions
- Rust 2018 style macro imports are now supported.
- In a Rust 2018 crate, all the macros can be brought into scope with
`import proptest::prelude::*;`.
- The proptest macros now accept trailing commas in more locations.
- Visibility modifiers can now be passed to `prop_compose!` without enclosing
them in brackets. Unfortunately, the old way could not continue to be
supported due to the way the `vis` macro matcher works.
### Nightly-only breakage
- The `nightly` feature, which was formerly required for using proptest with
`#[no_std]`, has been removed. References to the feature can simply be
deleted.
- When using the `unstable` feature and setting `default-features = false`, the
`AtomicI64` and `AtomicU64` types are not supported unless the `atomic64bit`
feature is enabled. This supports `no_std` usage on platforms which do not
support atomic 64-bit operations.
### Other Notes
- Generated strings are now much more likely to contain right-to-left override
characters.
- Most of the crate-level documentation has been relocated to the [Proptest
Book](https://altsysrq.github.io/proptest-book/proptest/index.html).
## 0.8.7
### New Additions
- Add `max_shrink_iters` and `max_shrink_time` options to test configuration to
allow capping the resources expended on shrinking test cases.
- Add `verbose` option to make proptest give details about what is happening as
the test executes.
- When a failure is saved to the persistence file, the message now also
includes the seed that was saved so that it can manually be added to the
appropriate file should the test have run somewhere where the updated file is
not accessible (for example, on a CI system).
### Bug Fixes
- `any::<SystemTime>()` now generates random values centred on the UNIX epoch
rather than always producing the current time.
### Other Notes
- When using forking, proptest will now detect conditions which cause the child
process to crash without running any tests, and will fail quickly instead of
respawning child processes.
## 0.8.6
### New Additions
- `Vec<S> where S: Strategy` is now itself a `Strategy` for producing
fixed-size `Vec`s whose values are derived from the respective strategies.
- It is now possible to configure the test runner to cache test results to
avoid spending time running identical tests. See `Config.result_cache`.
- Add `sample::Index`, a type for generating indices into runtime-sized slices
and vectors.
- Add `sample::Selector`, a type for picking items out of dynamically-created
iterables.
### Bug Fixes
- Fix panic when using `sample::subsequence` with an empty vector.
- Fix panic when using `sample::subsequence` with a size equal to the size of
the input vector.
- Fix sampled bitset strategies on integers not allowing to generate exactly
the same number of bits as the integer is wide.
### Other Notes
- Passing empty size ranges to functions requiring a non-empty size range now
panic with an explicit message immediately rather than causing an arithmetic
error when generating input values.
- There were a few cases where proptest would accept a `SizeRange` with an
inclusive maximum value of `usize::MAX`. Size ranges are now always clamped
to `usize::MAX - 1`.
## 0.8.5
### Bug Fixes
- Fix build when nightly features are enabled.
## 0.8.4
### Bug Fixes
- Nightly and no_std support work against latest nightly once again.
### New Additions
- Added `bits::bool_vec` for generating `Vec<bool>` as a bit set.
### Nightly-only breakage
- `impl Arbitrary for CollectionAllocErr` is temporarily removed pending it
being available outside the `alloc` crate again.
- `bits::bitset` is no longer available without the `bit-set` feature (enabled
by default), which is [not compatible with `#[no_std]`
environments](https://github.com/contain-rs/bit-vec/pull/51).
## 0.8.3
### Bug Fixes
- Fix that regex-based string generation could transpose the order of a literal
and a non-literal component.
## 0.8.2
### New Additions
- Macros which previously accepted `pattern in strategy` syntax to specify
arguments now also accept `pattern: type` syntax as shorthand for
`pattern in any::<type>()`.
- Closure-style `proptest!` invocation no longer requires the body to use block
syntax.
- Closure-style `proptest!` invocation now accepts custom configurations.
## 0.8.1
### New Additions
- `proptest!` now has form that accepts a closure. See the documentation for
the macro for more details.
### Bug Fixes
- Fix spurious warning about corrupt regression files. The files were not
corrupt but the parser was failing to handle the blank line at the end.
- The `multiplex_alloc!` and `multiplex_core!` macros which were
unintentionally exported in 0.8.0 are no longer exported. This is not
considered a breaking change since they were not supposed to be accessible,
and in any case would not have expanded into valid code in most other crates.
## 0.8.0
### New Additions
- A combinator `.prop_filter_map` has been added to `Strategy`.
It is similar to `.filter_map` for `Iterator` in that it is the
combination of `.prop_filter` and `.prop_map`.
- `i128` and `u128` are now supported without any feature flags and on stable.
- More implementations of `Arbitrary` are supported for `alloc` + `no_std` users.
- `size_range` now accepts inclusive ranges of form `low..=high` and `..=high`.
Thus, you can construct a `vec` strategy as: `vec(elt_strategy, low..=high)`
and `vec(elt_strategy, ..=high)`. This also applies to other functions
accepting `Into<SizeRange>`.
- `..= high` is now a valid strategy. Please note that `..= 1` will naturally
include numbers lower than `0` for sized types.
- `low..=high` is also a valid strategy.
- `Arbitrary` is implemented for `RangeInclusive<Idx>`, `RangeToInclusive`,
and `DecodeUtf16` on stable.
- Bitset strategies and `subsequence` now accept all range syntaxes.
### Bug Fixes
- Fix a race condition where a test failing due to running ever so slightly
over the set timeout could cause the test harness to converge to the
incorrect failing value, a non-failing value, or panic.
### Deprecations
- The type alias `ValueFor<S>` is now deprecated and will be removed in
version 0.9. You should just use `S::Value` instead.
### Breaking changes
- A minimum version of 1.27 of Rust is now required.
- `regex-syntax` version 0.6 is now used.
- `rand` version 0.5 is now used.
- As a consequence, the `FailurePersistence` trait will now use `[u8; 16]` seeds
instead of `[u32; 4]`. However, the stored failure persistence files using
the default `FileFailurePersistence` will still use `[u32; 4]` so your old
failure persistence files should still work.
- The RNG used by proptest has been changed to a PRNG `TestRng` which proptest
exposes. This is currently a simple new-type wrapper around `XorShiftRng`.
In the future, this will give us more freedom to make changes without breakage.
- The feature flag `i128_support` has been removed. The features it added are
now always supported.
- The associated type `Value` of `Strategy` has been renamed to `Tree`.
A new associated type `Value` has been added to `Strategy` which always refers
to the same type as `<S::Tree as ValueTree>::Value` for some strategy `S`.
This change allows you to write `-> impl Strategy<Value = T>` for functions
returning a `Strategy` generating `T`s. This is more ergonomic to use than
`-> impl Strategy<Value = impl ValueTree<Value = T>>`.
- The method `new_value` in `Strategy` has been renamed to `new_tree` to mirror
the renaming of `Value` to `Tree`.
- As a consequence change, the associated type `ValueTree` has been removed from
`Arbitrary`.
- The methods `run` and `run_one` on `TestRunner` now takes a function-under-test
that accepts the generated type by value instead of by reference instead.
This means that you don't need to write `ref value in my_strategy` and can
write `value in my_strategy` instead even if `typeof(value)` doesn't implement
`Copy`. This is also a step in the direction of allowing strategies to generate
references when generic associated types (GATs) land.
However, `ref value in my_strategy` will still be accepted, so not a lot of
breakage should come of this if you've used `proptest! { .. }`.
- `prop_compose!` no longer applies `.boxed()` to the strategy produced.
Therefore, `-> BoxedStrategy<T>` is no longer the correct type.
The new return type is `-> impl Strategy<Value = T>`.
If you want the old behaviour, you can use `.boxed()` yourself.
- `Arbitrary` for `SizeRange` changed its associated type to use `RangeInclusive`.
Same applies for `CString`.
- Many APIs now use `impl Trait` in argument position, which could affect code
using turbofishes to specify types explicitly.
- `char` APIs which formerly represented a range as `(start, end)` now require
`start..=end`.
### Nightly-only breakage
- As `std::io::{Chars, CharsError}` have been deprecated on nightly,
their `Arbitrary` implementations have been removed.
## 0.7.2
### Bug Fixes
- Fix that `bool` would not shrink correctly, leading to hangs when tests
taking `bool` parameters would fail in certain circumstances.
## 0.7.1
### New Additions
- It is now possible to run test cases in sub-processes. This allows using
proptest to test functions which may cause the test process to terminate
abruptly, such as by calling `abort()` or even suffering a segmentation
fault. This requires the "fork" feature, enabled by default.
- Added support for setting a timeout which applies on a per-test-case (i.e.,
single input rather than the whole test) basis. This allows using proptest to
find inputs which cause code to get stuck in infinite loops or exhibit other
pathological performance behaviour. This requires the "timeout" feature (and
transitively, the "fork" feature), enabled by default.
See also [the documentation](README.md#forking-and-timeouts) for these
features.
### Bug Fixes
- Fix that failure persistence file would be written to the incorrect location
in projects using workspaces. See
[#24](https://github.com/AltSysrq/proptest/issues/24) for more details and
instructions on how to migrate any persistence files that had been written to
the wrong location.
- Fix a case where `any::<ArgsOs>()` or `any::<VarsOs>()` could panic on
Windows.
### Nightly-only breakage
- Support for the `hashmap_core` crate is removed pending
https://github.com/Amanieu/hashmap_core/issues/3.
## 0.7.0
### Potential Breaking Changes
- The persistence system has been refactored to allow for
non-file-system based persistence. `FailurePersistence`
is now a trait, and the prior file-based enum which fulfilled
that purpose is now called `FileFailurePersistence` and implements
the generic trait. The default behavior has not changed.
- Reflecting the change to persistence, `Config.failure_persistence`
is now of type `Option<Box<FailurePersistence>>`.
- The `source_file` used as an optional reference point to the location of the
calling test is now tracked on the `Config` struct rather than the
`TestRunner`.
### New Additions
- Experimental support on nightly for working in `#![no_std]` environments has
been added. To use it, one must disable the default-features for proptest and
use the new "alloc" and "nightly" features. Currently access to a heap
allocator is still required.
## 0.6.0
### Potential Breaking Changes
- There is a small change of breakage if you've relied on `Recursive` using an
`Arc<BoxedStrategy<T>>` as `Recursive` now internally uses `BoxedStrategy<T>`
instead as well as expecting a `Fn(BoxedStrategy<T>) -> R` instead of
`Fn(Arc<BoxedStrategy<T>>) -> R`. In addition, the type of recursive
strategies has changed from `Recursive<BoxedStrategy<T>, F>` to just
`Recursive<T, F>`.
### Minor changes
- Reduced indirections and heap allocations inside `Recursive<T, F>` somewhat.
- `BoxedStrategy<T>` and `SBoxedStrategy<T>` now use `Arc` internally instead of
using `Box`. While this has marginal overhead, it also reduces the overhead
in `Recursive<T, F>`. The upside to this change is also that you can very
cheaply clone strategies.
- `Filter` is marginally faster.
### Bug Fixes
- Removed `impl Arbitrary for LocalKeyState` since `LocalKeyState` no longer
exists in the nightly compiler.
- Unstable features compile on latest nightly again.
## 0.5.1
### New Additions
- `proptest::strategy::Union` and `proptest::strategy::TupleUnion` now work
with weighted strategies even if the sum of the weights overflows a `u32`.
- Added `SIGNALING_NAN` strategy to generate signalling NaNs if supported by
the platform. Note that this is _not_ included in `ANY`.
### Bug Fixes
- Fixed values produced via `prop_recursive()` not shrinking from the recursive
to the non-recursive case.
- Fix that `QUIET_NAN` would generate signalling NaNs on most platforms on Rust
1.24.0 and later.
## 0.5.0
### Potential Breaking Changes
- There is a small chance of breakage if you've relied on the constraints put
on type inference by the closure in `leaf.prop_recursive(..)` having a fixed
output type. The output type is now any strategy that generates the same type
as `leaf`. This change is intended to make working with recursive types a bit
easier as you no longer have to use `.boxed()` inside the closure you pass to
`.prop_recursive(..)`.
- There is a small chance of breakage wrt. type inference due to the
introduction of `SizeRange`.
- There is a small chance of breakage wrt. type inference due to the
introduction of `Probability`.
- `BoxedStrategy` and `SBoxedStrategy` are now newtypes instead of being type
aliases. You will only experience breaking changes if you've directly
used `.boxed()` and not `(S)BoxedStrategy<T>` but rather
`Box<Strategy<Value = Box<ValueTree<Value = T>>>>`. The probability of
breakage is very small, but still possible. The benefit of this change
is that calling `.boxed()` or `.sboxed()` twice only boxes once. This can
happen in situations where you have functions `Strategy -> BoxedStrategy` or
with code generation.
- `proptest::char::ANY` has been removed. Any remaining uses must be replaced
by `proptest::char::any()`.
- `proptest::strategy::Singleton` has been removed. Any remaining uses must be
replaced by `proptest::strategy::Just`.
### New Additions
- Proptest now has an `Arbitrary` trait in `proptest::arbitrary` and re-exported
in the `proptest::prelude`. `Arbitrary` has also been `impl`emented for most
of the standard library. The trait provides a mechanism to define a canonical
`Strategy` for a given type just like `Arbitrary` in Haskell's QuickCheck.
Deriving for this trait will also be provided soon in the crate
`proptest_derive`. To use the canonical strategy for a certain type `T`,
you can simply use `any::<T>()`. This is the major new addition of this release.
- The `any_with`, `arbitrary`, `arbitrary_with` free functions in
the module `proptest::arbitrary`.
- The `ArbitraryF1` and `ArbitraryF2` traits in `proptest::arbitrary::functor`.
These are "higher order" `Arbitrary` traits that correspond to the `Arbitrary1`
and `Arbitrary2` type classes in Haskell's QuickCheck. They are mainly provided
to support a common set of container-like types in custom deriving self-recursive
types in `proptest_derive`. More on this later releases.
- The strategies in `proptest::option` and `proptest::result` now accept a type
`Probability` which is a wrapper around `f64`. Conversions from types such as
`f64` are provided to make the interface ergonomic to use. Users may also use
the `proptest::option::prob` function to explicitly construct the type.
- The strategies in `proptest::collections` now accept a type `SizeRange`
which is a wrapper around `Range<usize>`. Conversions from types
such as `usize` and `Range<usize>` are provided to make the interface
ergonomic to use. Users may also use the `proptest::collections::size_bounds`
function to explicitly construct the type.
- A `.prop_map_into()` operation on all strategies that map
using `Into<OutputType>`. This is a clearer and cheaper
operation than using `.prop_map(OutputType::from)`.
- A nonshrinking `LazyJust` strategy that can be used instead of `Just` when you
have non-`Clone` types.
- Anything that can be coerced to `fn() -> T` where `T: Debug` is a `Strategy`
where `ValueFor<fn() -> T> == T`. This is intended to make it easier to reuse
proptest for unit tests with manual input space partition where `fn() -> T`
provides fixtures.
### Minor changes
- Relaxed the constraints of `btree_map` removing `'static`.
- Reduced the heap allocation inside `Recursive` somewhat.
## 0.4.2
### Bug Fixes
- The `unstable` feature now works again.
## 0.4.1
### New Additions
- The `proptest::num::f32` and `proptest::num::f64` modules now have additional
constants (e.g., `POSITIVE`, `SUBNORMAL`, `INFINITE`) which can be used to
generate subsets of the floating-point domain by class and sign.
### Bug Fixes
- `proptest::num::f32::ANY` and `proptest::num::f64::ANY` now actually produce
arbitrary values. Previously, they had the same effect as `0.0..1.0`. While
this fix is a very substantial change in behaviour, it was not considered a
breaking change since (a) the new behaviour is consistent with the
documentation and expectations, (b) it's quite unlikely anyone was depending
on the old behaviour since anyone who wanted that range would have written it
out, and (c) Proptest isn't generally a transitive dependency so the chance
of this update happening "by surprise" is low.
## 0.4.0
### Deprecations and Potential Breaking Changes
- `proptest::char::ANY` replaced with `proptest::char::any()`.
`proptest::char::ANY` is present but deprecated, and will be removed in
proptest 0.5.0.
- Instead of returning `-> Result<Self::Value, String>`, strategies are
expected to return `-> Result<Self::Value, Reason>` instead. `Reason` reduces
the amount of heap allocations, especially for `.prop_filter(..)` where you
may now also pass in `&'static str`. You will only experience breaks if
you've written your own strategy types or if you've used
`TestCaseError::Reject` or `TestCaseError::Fail` explicitly.
- Update of externally-visible crate `rand` to `0.4.2`.
### New Additions
- Added `proptest::test_runner::Reason` which allows you to avoid heap
allocation in some places and may be used to make the API richer in the
future without incurring more breaking changes.
- Added a type alias `proptest::strategy::NewTree<S>` where `S: Strategy`
defined as: `type NewTree<S> = Result<<S as Strategy>::Value, Rejection>`.
## 0.3.4
### Bug Fixes
- Cases where `file!()` returns a relative path, such as on Windows, are now
handled more reasonably. See
[#24](https://github.com/AltSysrq/proptest/issues/24) for more details and
instructions on how to migrate any persistence files that had been written to
the wrong location.
## 0.3.3
Boxing Day Special
### New Additions
- Added support for `i128` and `u128`. Since this is an unstable feature in
Rust, this is hidden behind the feature `unstable` which you have to
explicitly opt into in your `Cargo.toml` file.
- Failing case persistence. By default, when a test fails, Proptest will now
save the seed for the failing test to a file, and later runs will test the
persisted failing cases before generating new ones.
- Added `UniformArrayStrategy` and helper functions to simplify generating
homogeneous arrays with non-`Copy` inner strategies.
- Trait `rand::Rng` and struct `rand::XorShiftRng` are now included in
`proptest::prelude`.
### Bug Fixes
- Fix a case where certain combinations of strategies, like two
`prop_shuffle()`s in close proximity, could result in low-quality randomness.
## 0.3.2
### New Additions
- Added `SampledBitSetStrategy` to generate bit sets based on size
distribution.
- Added `Strategy::sboxed()` and `SBoxedStrategy` to make `Send + Sync` boxed
strategies.
- `RegexGeneratorStrategy` is now `Send` and `Sync`.
- Added a type alias `ValueFor<S>` where `S: Strategy`. This is a shorter way
to refer to: `<<S as Strategy>::Value as ValueTree>::Value`.
- Added a type alias `type W<T> = (u32, T)` for a weighted strategy `T` in the
context of union strategies.
- `TestRunner` now implements `Default`.
- Added `Config::with_cases(number_of_cases: u32) -> Config` for simpler
construction of a `Config` that only differs by the number of test cases.
- All default fields of `Config` can now be overridden by setting environment
variables. See the docs of that struct for more details.
- Bumped dependency `rand = "0.3.18"`.
- Added `proptest::sample::subsequence` which returns a strategy generating
subsequences, of the source `Vec`, with a size within the given `Range`.
- Added `proptest::sample::select` which returns a strategy selecting exactly
one value from another collection.
- Added `prop_perturb` strategy combinator.
- Added `strategy::check_strategy_sanity()` function to do sanity checks on the
shrinking implementation of a strategy.
- Added `prop_shuffle` strategy combinator.
- Added `strategy::Fuse` adaptor.
### Bug Fixes
- Fix bug where `Vec`, array and tuple shrinking could corrupt the state of
their inner values, for example leading to out-of-range integers.
- Fix bug where `Flatten` (a.k.a. the `prop_flat_map` combinator) could fail to
converge to a failing test case during shrinking.
- Fix `TupleUnion` sometimes panicking during shrinking if there were more than
two choices.
## 0.3.1
### New Additions
- Added `CharStrategy::new_borrowed`.
## 0.3.0
### New Additions
- `Union` now supports weighting via `Union::new_weighted`. Corresponding
syntax to specify weights is also available in `prop_oneof!`.
- Added `TupleUnion`, which works like `Union` but permits doing static
dispatch even with heterogeneous delegate strategies.
- `prop_oneof!` is smarter about how it combines the input strategies.
- Added `option` module to generate weighted or unweighted `Option` types.
- Added `result` module to generate weighted or unweighted `Result` types.
- All `bits` submodules now have a `masked` function to create a strategy for
generating subsets of an arbitrary bitmask.
### Potential Breaking Changes
- `Union::new` now has a generic argument type which could impact type
inference.
- The concrete types produced by `prop_oneof!` have changed.
- API functions which used to return `BoxedStrategy` now return a specific
type.
- `BitSetStrategy<T>` is no longer `Copy` for non-`Copy` types `T` nor `Debug`
for non-`Debug` types `T`.
- `BitSetLike::max` has been renamed to `BitSetLike::len`.
## 0.2.1
### New Additions
- Added `prop_assert!` macro family to assert without panicking, for quieter
test failure modes.
- New `prelude` module for easier importing of important things.
- Renamed `Singleton` to `Just`. (The old name is still available.)
- Failure messages produced by `proptest!` are now much more readable.
- Added in-depth tutorial.
## 0.2.0
### Breaking Changes
- `Strategy` now requires `std::fmt::Debug`.
### New Additions
- `Strategy` now has a family of `prop_flat_map()` combinators for producing
dynamic and higher-order strategies.
- `Strategy` has a `prop_recursive()` combinator which allows generating
recursive structures.
- Added `proptest::bool::weighted()` to pull booleans from a weighted
distribution.
- New `prop_oneof!` macro makes it easier to select from one of several
strategies.
- New `prop_compose!` macro to simplify writing most types of custom
strategies.
## 0.1.1
### New Additions
Add `strategy::NoShrink`, `Strategy::no_shrink()`.