proptest

New Features

• Added bits::u128 and bits::i128 strategies for 128-bit integer bit set generation. (#311)
• Added support for f16 feature-gated by "f16" or "unstable". (#638)

Breaking Changes

• The minimum supported Rust version has been increased to 1.84.0. (#612)

New Features

• Added a memory-efficient strategy for sampling subsets from ranges without replacement. (#586)

Other Notes

• Updated convert_case requirement from 0.6 to 0.11. (#623)
• Updated trybuild requirement from =1.0.113 to =1.0.115. (#624)

prep 1.9.0 release (#607)

Breaking Changes

• The minimum supported Rust version has been increased to 1.82.0. (#605)

New Features

• Added ProptestResultExt trait with prop_assume_ok helper method for converting Result types to test outcomes. (#589)

Other Notes

• Replaced lazy_static dependency with std::sync::LazyLock. (#546)
• Fixed doctest and cleaned up warnings. (#606)

New Features

• Implement Arbitrary for Saturating<T>. (#585)
• Allow prop_assert! with trailing comma. (#581)

Bug Fixes

• Fix arithmetic overflow on 32-bit processors. (#596)
• Sanitize user-facing macros to use fully qualified paths, preventing conflicts with user code. (#584)

Other Notes

• Updated rand dependency from 0.8 to 0.9.
• Bump all dependencies to latest compatible with MSRV 1.66.

New Features

• Added handle-panics feature which enables catching panics raised in tests and turning them into failures. (#525)
• Exit early if shrink disabled. (#520)
• Add Config::with_failure_persistence. A convenience constructor making use of a generic parameter over FailurePersistence impls and hiding the Some(Box::new(...)). (#508)
• Add From's for SizeRange and Probability. (#498)
• When running persisted regressions, the most recently added regression is now run first. (#496)

Bug Fixes

• Fix WebAssembly support. Hides a few paths, that fail at runtime on wasm32-unknown-unknown, under conditional compilation. (#519)
• Fix incorrectly reading environment configuration. Previously controlling proptest configuration via env vars was not properly applied. This caused vars like PROPTEST_MAX_DEFAULT_SIZE_RANGE to be not be properly applied, leading to unexpected behavior. (#457)
• Allow trailing comma in prop_assert_eq/ne like std. (#510)

Other Notes

• Add no_std to alloc contexts. no_std must be used explicitly with alloc. Updated CI and documentation to reflect this. (#528)
• Make libm optional in a std environment. (#524)
• Update bit-set and bit-vec to 0.8.0. (#501)
• Removed unused frunk feature. (#498)

New Features

• Setting PROPTEST_MAX_DEFAULT_SIZE_RANGE now customizes the default SizeRange used by the default strategies for collections (like Vec). The default remains 100.
• Empty ranges panic during tree creation instead of during sampling.

Documentation

• Reference the derive macro in Arbitrary's documentation
• Fix broken links in the book

Bug Fixes

• Fixed issue where config contextualization would clobber existing failure persistence config

Breaking Changes

• The minimum supported Rust version has been increased to 1.65.0.

Other Notes

• regex-syntax updated from 0.7 to 0.8
• Fixed new clippies
• Fixed nightly build where Generator was renamed to Coroutine

Other Notes

• bit-set updated from 0.5.0 to 0.5.2 to ensure minimum compatible version with bit-vec 0.6

Breaking Changes

• The minimum supported Rust version has been increased to 1.64.0.

New Features

• Adds Arbitrary impl for PathBuf
• Permit use of (?-u) in byte-regex strategies, allowing non-utf-8 bytes to be generated

Book

• Various small fixes -- typos, formatting
• Removal of custom theme
• Add book page for Tips and Best Practices

Other Notes

• regex-syntax version 0.7 is now used.
• Print a seed to stderr for a failed test even when a regressions file is already present.
• Fixed a performance issue with VarBitSet::saturated that can slow down VecStrategy
• Remove use of rust feature core_intrinsics
• Remove no longer needed "break-dead-code" feature
• Disable clippy::arc_with_non_send_sync
• Remove dependency on byteorder

Breaking Changes

• PROPTEST_ environment variables now take precedence over tests' non-default configuration.

Bug Fixes

• Don't implement Arbitrary for NonZeroU128 and NonZeroI128 on wasm targets where u128 and i128 Arbitrary impls don't exist

New Features

Other Notes

• Minimal failing input is now printed using debug pretty-printing
• Made public VarBitSet, SizeRange read-only methods and num sampling functions in preparation for release of a proptest-state-machine crate.
• Removed dependency on quick_error
• Start publishing MSRV

Bug Fixes

• Sampling from large ranges of floats such as (0f32).. no longer panics with newer versions of the rand crate
• [dependencies.x86] was bumped to latest current version. x86 crate does was on a very old version 0.33.0 which used a removed macro from rust.
• The calculation for the arbitrary impl of Layout was using a max_size that was too large and overflowing Layout. This has been fixed.
• Test for arbitrary AllocError was referring to AllocErr which does not exist, this was fixed.
• NoneError has been removed from rust so it was subsequently removed from proptest. It was blocking compilation. evidence: https://github.com/rust-lang/rust/issues/85614
• try_reserve is stable so removed from unstable features
• try_trait has been changed to try_trait_v2 so that was adjusted in Cargo.toml.
• prop_assert_ne! now uses fully qualified prop_assert_eq!
• Persisted tests are not counted against the number of cases to run

New Features

• Add Arbitrary impls for arrays of all sizes using const generics
• Add Arbitrary impls for core::num::NonZero*
• Adds ability to disable failure persistence via env var PROPTEST_DISABLE_FAILURE_PERSISTENCE

Other Notes

• proptest no longer depends on the quick-error crate.

Breaking Changes

• The minimum supported Rust version has been increased to 1.50.0.

• The version of the rand crate has been increased to 0.8.

• Due to changes in the getrandom crate, if you wish to use proptest on the wasm32-unknown-unknown target, you must manually add a dependency on that crate and enable a feature that will allow it to work. Refer to the getrandom crate documentation for more information.

Bug Fixes

• prop_shuffle() can now produce all permutations.

New Features

• Tuple strategies up to 12 elements are now supported, for parity with the blanket implementations that std provides.

New Features

• Added RngAlgorithm::Recorder and supporting APIs which allow capturing random data generated as part of generating a value or running a test.

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 dependency (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 when running forked tests.

• The PassThrough RNG algorithm now returns 0 instead of panicking when it runs out of entropy.

Bug Fixes

• Fixed #186, a Rust future-compatibility issue.

Bug Fixes

• Fixed a Rust future-compatibility issue (https://github.com/rust-lang/rust/pull/65819).

New Additions

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.

This is a minor release to correct some packaging errors. The license files are now included in the files published to crates.io, and some unneeded files are now excluded.

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 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.

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 TestRngs.

• 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 which prevents building with -C link-dead-code. Please see this issue for details: https://github.com/proptest-rs/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.

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.

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.

New Additions

• Vec<S> where S: Strategy is now itself a Strategy for producing fixed-size Vecs 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.

Bug Fixes

• Fix build when nightly features are enabled.

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.

Bug Fixes

• Fix that regex-based string generation could transpose the order of a literal and a non-literal component.

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.

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.

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 Ts. 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.

Bug Fixes

• Fix that bool would not shrink correctly, leading to hangs when tests taking bool parameters would fail in certain circumstances.

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 for these features.

Bug Fixes

• Fix that failure persistence file would be written to the incorrect location in projects using workspaces. See #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.

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.

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.

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.

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 implemented 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.

Bug Fixes

• The unstable feature now works again.

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.

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>.

Bug Fixes

• Cases where file!() returns a relative path, such as on Windows, are now handled more reasonably. See #24 for more details and instructions on how to migrate any persistence files that had been written to the wrong location.

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.

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.

New Additions

• Added CharStrategy::new_borrowed.

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.

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.

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.

New Additions

Add strategy::NoShrink, Strategy::no_shrink().