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//- // Copyright 2017, 2018 The proptest developers // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. use core::cmp; use crate::std_facade::{fmt, Box, Rc, Arc}; use crate::strategy::*; use crate::test_runner::*; //============================================================================== // Traits //============================================================================== /// A new [`ValueTree`] from a [`Strategy`] when [`Ok`] or otherwise [`Err`] /// when a new value-tree can not be produced for some reason such as /// in the case of filtering with a predicate which always returns false. /// You should pass in your strategy as the type parameter. /// /// [`Strategy`]: trait.Strategy.html /// [`ValueTree`]: trait.ValueTree.html /// [`Ok`]: https://doc.rust-lang.org/nightly/std/result/enum.Result.html#variant.Ok /// [`Err`]: https://doc.rust-lang.org/nightly/std/result/enum.Result.html#variant.Err pub type NewTree<S> = Result<<S as Strategy>::Tree, Reason>; /// A strategy for producing arbitrary values of a given type. /// /// `fmt::Debug` is a hard requirement for all strategies currently due to /// `prop_flat_map()`. This constraint will be removed when specialisation /// becomes stable. #[must_use = "strategies do nothing unless used"] pub trait Strategy : fmt::Debug { /// The value tree generated by this `Strategy`. type Tree : ValueTree<Value = Self::Value>; /// The type of value used by functions under test generated by this Strategy. /// /// This corresponds to the same type as the associated type `Value` /// in `Self::Tree`. It is provided here to simplify usage particularly /// in conjunction with `-> impl Strategy<Value = MyType>`. type Value : fmt::Debug; /// Generate a new value tree from the given runner. /// /// This may fail if there are constraints on the generated value and the /// generator is unable to produce anything that satisfies them. Any /// failure is wrapped in `TestError::Abort`. /// /// This method is generally expected to be deterministic. That is, given a /// `TestRunner` with its RNG in a particular state, this should produce an /// identical `ValueTree` every time. Non-deterministic strategies do not /// cause problems during normal operation, but they do break failure /// persistence since it is implemented by simply saving the seed used to /// generate the test case. fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self>; /// Returns a strategy which produces values transformed by the function /// `fun`. /// /// There is no need (or possibility, for that matter) to define how the /// output is to be shrunken. Shrinking continues to take place in terms of /// the source value. /// /// `fun` should be a deterministic function. That is, for a given input /// value, it should produce an equivalent output value on every call. /// Proptest assumes that it can call the function as many times as needed /// to generate as many identical values as needed. For this reason, `F` is /// `Fn` rather than `FnMut`. fn prop_map<O : fmt::Debug, F : Fn (Self::Value) -> O> (self, fun: F) -> Map<Self, F> where Self : Sized { Map { source: self, fun: Arc::new(fun) } } /// Returns a strategy which produces values of type `O` by transforming /// `Self` with `Into<O>`. /// /// You should always prefer this operation instead of `prop_map` when /// you can as it is both clearer and also currently more efficient. /// /// There is no need (or possibility, for that matter) to define how the /// output is to be shrunken. Shrinking continues to take place in terms of /// the source value. fn prop_map_into<O : fmt::Debug>(self) -> MapInto<Self, O> where Self : Sized, Self::Value: Into<O> { MapInto::new(self) } /// Returns a strategy which produces values transformed by the function /// `fun`, which is additionally given a random number generator. /// /// This is exactly like `prop_map()` except for the addition of the second /// argument to the function. This allows introducing chaotic variations to /// generated values that are not easily expressed otherwise while allowing /// shrinking to proceed reasonably. /// /// During shrinking, `fun` is always called with an identical random /// number generator, so if it is a pure function it will always perform /// the same perturbation. /// /// ## Example /// /// ``` /// // The prelude also gets us the `Rng` trait. /// use proptest::prelude::*; /// /// proptest! { /// #[test] /// fn test_something(a in (0i32..10).prop_perturb( /// // Perturb the integer `a` (range 0..10) to a pair of that /// // integer and another that's ± 10 of it. /// // Note that this particular case would be better implemented as /// // `(0i32..10, -10i32..10).prop_map(|(a, b)| (a, a + b))` /// // but is shown here for simplicity. /// |centre, rng| (centre, centre + rng.gen_range(-10, 10)))) /// { /// // Test stuff /// } /// } /// # fn main() { } /// ``` fn prop_perturb<O : fmt::Debug, F : Fn (Self::Value, TestRng) -> O> (self, fun: F) -> Perturb<Self, F> where Self : Sized { Perturb { source: self, fun: Arc::new(fun) } } /// Maps values produced by this strategy into new strategies and picks /// values from those strategies. /// /// `fun` is used to transform the values produced by this strategy into /// other strategies. Values are then chosen from the derived strategies. /// Shrinking proceeds by shrinking individual values as well as shrinking /// the input used to generate the internal strategies. /// /// ## Shrinking /// /// In the case of test failure, shrinking will not only shrink the output /// from the combinator itself, but also the input, i.e., the strategy used /// to generate the output itself. Doing this requires searching the new /// derived strategy for a new failing input. The combinator will generate /// up to `Config::cases` values for this search. /// /// As a result, nested `prop_flat_map`/`Flatten` combinators risk /// exponential run time on this search for new failing values. To ensure /// that test failures occur within a reasonable amount of time, all of /// these combinators share a single "flat map regen" counter, and will /// stop generating new values if it exceeds `Config::max_flat_map_regens`. /// /// ## Example /// /// Generate two integers, where the second is always less than the first, /// without using filtering: /// /// ``` /// use proptest::prelude::*; /// /// proptest! { /// # /* /// #[test] /// # */ /// fn test_two( /// // Pick integers in the 1..65536 range, and derive a strategy /// // which emits a tuple of that integer and another one which is /// // some value less than it. /// (a, b) in (1..65536).prop_flat_map(|a| (Just(a), 0..a)) /// ) { /// prop_assert!(b < a); /// } /// } /// # /// # fn main() { test_two(); } /// ``` /// /// ## Choosing the right flat-map /// /// `Strategy` has three "flat-map" combinators. They look very similar at /// first, and can be used to produce superficially identical test results. /// For example, the following three expressions all produce inputs which /// are 2-tuples `(a,b)` where the `b` component is less than `a`. /// /// ```no_run /// # #![allow(unused_variables)] /// use proptest::prelude::*; /// /// let flat_map = (1..10).prop_flat_map(|a| (Just(a), 0..a)); /// let ind_flat_map = (1..10).prop_ind_flat_map(|a| (Just(a), 0..a)); /// let ind_flat_map2 = (1..10).prop_ind_flat_map2(|a| 0..a); /// ``` /// /// The three do differ however in terms of how they shrink. /// /// For `flat_map`, both `a` and `b` will shrink, and the invariant that /// `b < a` is maintained. This is a "dependent" or "higher-order" strategy /// in that it remembers that the strategy for choosing `b` is dependent on /// the value chosen for `a`. /// /// For `ind_flat_map`, the invariant `b < a` is maintained, but only /// because `a` does not shrink. This is due to the fact that the /// dependency between the strategies is not tracked; `a` is simply seen as /// a constant. /// /// Finally, for `ind_flat_map2`, the invariant `b < a` is _not_ /// maintained, because `a` can shrink independently of `b`, again because /// the dependency between the two variables is not tracked, but in this /// case the derivation of `a` is still exposed to the shrinking system. /// /// The use-cases for the independent flat-map variants is pretty narrow. /// For the majority of cases where invariants need to be maintained and /// you want all components to shrink, `prop_flat_map` is the way to go. /// `prop_ind_flat_map` makes the most sense when the input to the map /// function is not exposed in the output and shrinking across strategies /// is not expected to be useful. `prop_ind_flat_map2` is useful for using /// related values as starting points while not constraining them to that /// relation. fn prop_flat_map<S : Strategy, F : Fn (Self::Value) -> S> (self, fun: F) -> Flatten<Map<Self, F>> where Self : Sized { Flatten::new(Map { source: self, fun: Arc::new(fun) }) } /// Maps values produced by this strategy into new strategies and picks /// values from those strategies while considering the new strategies to be /// independent. /// /// This is very similar to `prop_flat_map()`, but shrinking will *not* /// attempt to shrink the input that produces the derived strategies. This /// is appropriate for when the derived strategies already fully shrink in /// the desired way. /// /// In most cases, you want `prop_flat_map()`. /// /// See `prop_flat_map()` for a more detailed explanation on how the /// three flat-map combinators differ. fn prop_ind_flat_map<S : Strategy, F : Fn (Self::Value) -> S> (self, fun: F) -> IndFlatten<Map<Self, F>> where Self : Sized { IndFlatten(Map { source: self, fun: Arc::new(fun) }) } /// Similar to `prop_ind_flat_map()`, but produces 2-tuples with the input /// generated from `self` in slot 0 and the derived strategy in slot 1. /// /// See `prop_flat_map()` for a more detailed explanation on how the /// three flat-map combinators differ differ. fn prop_ind_flat_map2<S : Strategy, F : Fn (Self::Value) -> S> (self, fun: F) -> IndFlattenMap<Self, F> where Self : Sized { IndFlattenMap { source: self, fun: Arc::new(fun) } } /// Returns a strategy which only produces values accepted by `fun`. /// /// This results in a very naïve form of rejection sampling and should only /// be used if (a) relatively few values will actually be rejected; (b) it /// isn't easy to express what you want by using another strategy and/or /// `map()`. /// /// There are a lot of downsides to this form of filtering. It slows /// testing down, since values must be generated but then discarded. /// Proptest only allows a limited number of rejects this way (across the /// entire `TestRunner`). Rejection can interfere with shrinking; /// particularly, complex filters may largely or entirely prevent shrinking /// from substantially altering the original value. /// /// Local rejection sampling is still preferable to rejecting the entire /// input to a test (via `TestCaseError::Reject`), however, and the default /// number of local rejections allowed is much higher than the number of /// whole-input rejections. /// /// `whence` is used to record where and why the rejection occurred. fn prop_filter<R: Into<Reason>, F : Fn (&Self::Value) -> bool> (self, whence: R, fun: F) -> Filter<Self, F> where Self : Sized { Filter::new(self, whence.into(), fun) } /// Returns a strategy which only produces transformed values where `fun` /// returns `Some(value)` and rejects those where `fun` returns `None`. /// /// Using this method is preferable to using `.prop_map(..).prop_filter(..)`. /// /// This results in a very naïve form of rejection sampling and should only /// be used if (a) relatively few values will actually be rejected; (b) it /// isn't easy to express what you want by using another strategy and/or /// `map()`. /// /// There are a lot of downsides to this form of filtering. It slows /// testing down, since values must be generated but then discarded. /// Proptest only allows a limited number of rejects this way (across the /// entire `TestRunner`). Rejection can interfere with shrinking; /// particularly, complex filters may largely or entirely prevent shrinking /// from substantially altering the original value. /// /// Local rejection sampling is still preferable to rejecting the entire /// input to a test (via `TestCaseError::Reject`), however, and the default /// number of local rejections allowed is much higher than the number of /// whole-input rejections. /// /// `whence` is used to record where and why the rejection occurred. fn prop_filter_map<F : Fn (Self::Value) -> Option<O>, O : fmt::Debug> (self, whence: impl Into<Reason>, fun: F) -> FilterMap<Self, F> where Self : Sized { FilterMap::new(self, whence.into(), fun) } /// Returns a strategy which picks uniformly from `self` and `other`. /// /// When shrinking, if a value from `other` was originally chosen but that /// value can be shrunken no further, it switches to a value from `self` /// and starts shrinking that. /// /// Be aware that chaining `prop_union` calls will result in a very /// right-skewed distribution. If this is not what you want, you can call /// the `.or()` method on the `Union` to add more values to the same union, /// or directly call `Union::new()`. /// /// Both `self` and `other` must be of the same type. To combine /// heterogeneous strategies, call the `boxed()` method on both `self` and /// `other` to erase the type differences before calling `prop_union()`. fn prop_union(self, other: Self) -> Union<Self> where Self : Sized { Union::new(vec![self, other]) } /// Generate a recursive structure with `self` items as leaves. /// /// `recurse` is applied to various strategies that produce the same type /// as `self` with nesting depth _n_ to create a strategy that produces the /// same type with nesting depth _n+1_. Generated structures will have a /// depth between 0 and `depth` and will usually have up to `desired_size` /// total elements, though they may have more. `expected_branch_size` gives /// the expected maximum size for any collection which may contain /// recursive elements and is used to control branch probability to achieve /// the desired size. Passing a too small value can result in trees vastly /// larger than desired. /// /// Note that `depth` only counts branches; i.e., `depth = 0` is a single /// leaf, and `depth = 1` is a leaf or a branch containing only leaves. /// /// In practise, generated values usually have a lower depth than `depth` /// (but `depth` is a hard limit) and almost always under /// `expected_branch_size` (though it is not a hard limit) since the /// underlying code underestimates probabilities. /// /// Shrinking shrinks both the inner values and attempts switching from /// recursive to non-recursive cases. /// /// ## Example /// /// ```rust,norun /// # #![allow(unused_variables)] /// use std::collections::HashMap; /// /// use proptest::prelude::*; /// /// /// Define our own JSON AST type /// #[derive(Debug, Clone)] /// enum JsonNode { /// Null, /// Bool(bool), /// Number(f64), /// String(String), /// Array(Vec<JsonNode>), /// Map(HashMap<String, JsonNode>), /// } /// /// # fn main() { /// # /// // Define a strategy for generating leaf nodes of the AST /// let json_leaf = prop_oneof![ /// Just(JsonNode::Null), /// prop::bool::ANY.prop_map(JsonNode::Bool), /// prop::num::f64::ANY.prop_map(JsonNode::Number), /// ".*".prop_map(JsonNode::String), /// ]; /// /// // Now define a strategy for a whole tree /// let json_tree = json_leaf.prop_recursive( /// 4, // No more than 4 branch levels deep /// 64, // Target around 64 total elements /// 16, // Each collection is up to 16 elements long /// |element| prop_oneof![ /// // NB `element` is an `Arc` and we'll need to reference it twice, /// // so we clone it the first time. /// prop::collection::vec(element.clone(), 0..16) /// .prop_map(JsonNode::Array), /// prop::collection::hash_map(".*", element, 0..16) /// .prop_map(JsonNode::Map) /// ]); /// # } /// ``` fn prop_recursive<R : Strategy<Value = Self::Value> + 'static, F : Fn (BoxedStrategy<Self::Value>) -> R> (self, depth: u32, desired_size: u32, expected_branch_size: u32, recurse: F) -> Recursive<Self::Value, F> where Self : Sized + 'static { Recursive::new(self, depth, desired_size, expected_branch_size, recurse) } /// Shuffle the contents of the values produced by this strategy. /// /// That is, this modifies a strategy producing a `Vec`, slice, etc, to /// shuffle the contents of that `Vec`/slice/etc. /// /// Initially, the value is fully shuffled. During shrinking, the input /// value will initially be unchanged while the result will gradually be /// restored to its original order. Once de-shuffling either completes or /// is cancelled by calls to `complicate()` pinning it to a particular /// permutation, the inner value will be simplified. /// /// ## Example /// /// ``` /// use proptest::prelude::*; /// /// static VALUES: &'static [u32] = &[0, 1, 2, 3, 4]; /// /// fn is_permutation(orig: &[u32], mut actual: Vec<u32>) -> bool { /// actual.sort(); /// orig == &actual[..] /// } /// /// proptest! { /// # /* /// #[test] /// # */ /// fn test_is_permutation( /// ref perm in Just(VALUES.to_owned()).prop_shuffle() /// ) { /// assert!(is_permutation(VALUES, perm.clone())); /// } /// } /// # /// # fn main() { test_is_permutation(); } /// ``` fn prop_shuffle(self) -> Shuffle<Self> where Self : Sized, Self::Value : Shuffleable { Shuffle(self) } /// Erases the type of this `Strategy` so it can be passed around as a /// simple trait object. /// /// See also `sboxed()` if this `Strategy` is `Send` and `Sync` and you /// want to preserve that information. /// /// Strategies of this type afford cheap shallow cloning via reference /// counting by using an `Arc` internally. fn boxed(self) -> BoxedStrategy<Self::Value> where Self : Sized + 'static { BoxedStrategy(Arc::new(BoxedStrategyWrapper(self))) } /// Erases the type of this `Strategy` so it can be passed around as a /// simple trait object. /// /// Unlike `boxed()`, this conversion retains the `Send` and `Sync` traits /// on the output. /// /// Strategies of this type afford cheap shallow cloning via reference /// counting by using an `Arc` internally. fn sboxed(self) -> SBoxedStrategy<Self::Value> where Self : Sized + Send + Sync + 'static { SBoxedStrategy(Arc::new(BoxedStrategyWrapper(self))) } /// Wraps this strategy to prevent values from being subject to shrinking. /// /// Suppressing shrinking is useful when testing things like linear /// approximation functions. Ordinarily, proptest will tend to shrink the /// input to the function until the result is just barely outside the /// acceptable range whereas the original input may have produced a result /// far outside of it. Since this makes it harder to see what the actual /// problem is, making the input `NoShrink` allows learning about inputs /// that produce more incorrect results. fn no_shrink(self) -> NoShrink<Self> where Self : Sized { NoShrink(self) } } /// A generated value and its associated shrinker. /// /// Conceptually, a `ValueTree` represents a spectrum between a "minimally /// complex" value and a starting, randomly-chosen value. For values such as /// numbers, this can be thought of as a simple binary search, and this is how /// the `ValueTree` state machine is defined. /// /// The `ValueTree` state machine notionally has three fields: low, current, /// and high. Initially, low is the "minimally complex" value for the type, and /// high and current are both the initially chosen value. It can be queried for /// its current state. When shrinking, the controlling code tries simplifying /// the value one step. If the test failure still happens with the simplified /// value, further simplification occurs. Otherwise, the code steps back up /// towards the prior complexity. /// /// The main invariants here are that the "high" value always corresponds to a /// failing test case, and that repeated calls to `complicate()` will return /// `false` only once the "current" value has returned to what it was before /// the last call to `simplify()`. /// /// While it would be possible for default do-nothing implementations of /// `simplify()` and `complicate()` to be provided, this was not done /// deliberately since the majority of strategies will want to define their own /// shrinking anyway, and the minority that do not must call it out explicitly /// by their own implementation. pub trait ValueTree { /// The type of the value produced by this `ValueTree`. type Value : fmt::Debug; /// Returns the current value. fn current(&self) -> Self::Value; /// Attempts to simplify the current value. Notionally, this sets the /// "high" value to the current value, and the current value to a "halfway /// point" between high and low, rounding towards low. /// /// Returns whether any state changed as a result of this call. This does /// not necessarily imply that the value of `current()` has changed, since /// in the most general case, it is not possible for an implementation to /// determine this. /// /// This call needs to correctly handle being called even immediately after /// it had been called previously and returned `false`. fn simplify(&mut self) -> bool; /// Attempts to partially undo the last simplification. Notionally, this /// sets the "low" value to one plus the current value, and the current /// value to a "halfway point" between high and the new low, rounding /// towards low. /// /// Returns whether any state changed as a result of this call. This does /// not necessarily imply that the value of `current()` has changed, since /// in the most general case, it is not possible for an implementation to /// determine this. /// /// It is usually expected that, immediately after a call to `simplify()` /// which returns true, this call will itself return true. However, this is /// not always the case; in some strategies, particularly those that use /// some form of rejection sampling, the act of trying to simplify may /// change the state such that `simplify()` returns true, yet ultimately /// left the resulting value unchanged, in which case there is nothing left /// to complicate. /// /// This call does not need to gracefully handle being called before /// `simplify()` was ever called, but does need to correctly handle being /// called even immediately after it had been called previously and /// returned `false`. fn complicate(&mut self) -> bool; } //============================================================================== // NoShrink //============================================================================== /// Wraps a `Strategy` or `ValueTree` to suppress shrinking of generated /// values. /// /// See `Strategy::no_shrink()` for more details. #[derive(Clone, Copy, Debug)] #[must_use = "strategies do nothing unless used"] pub struct NoShrink<T>(T); impl<T : Strategy> Strategy for NoShrink<T> { type Tree = NoShrink<T::Tree>; type Value = T::Value; fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> { self.0.new_tree(runner).map(NoShrink) } } impl<T : ValueTree> ValueTree for NoShrink<T> { type Value = T::Value; fn current(&self) -> T::Value { self.0.current() } fn simplify(&mut self) -> bool { false } fn complicate(&mut self) -> bool { false } } //============================================================================== // Trait objects //============================================================================== macro_rules! proxy_strategy { ($typ:ty $(, $lt:tt)*) => { impl<$($lt,)* S : Strategy + ?Sized> Strategy for $typ { type Tree = S::Tree; type Value = S::Value; fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> { (**self).new_tree(runner) } } }; } proxy_strategy!(Box<S>); proxy_strategy!(&'a S, 'a); proxy_strategy!(&'a mut S, 'a); proxy_strategy!(Rc<S>); proxy_strategy!(Arc<S>); impl<T : ValueTree + ?Sized> ValueTree for Box<T> { type Value = T::Value; fn current(&self) -> Self::Value { (**self).current() } fn simplify(&mut self) -> bool { (**self).simplify() } fn complicate(&mut self) -> bool { (**self).complicate() } } /// A boxed `ValueTree`. type BoxedVT<T> = Box<dyn ValueTree<Value = T>>; /// A boxed `Strategy` trait object as produced by `Strategy::boxed()`. /// /// Strategies of this type afford cheap shallow cloning via reference /// counting by using an `Arc` internally. #[derive(Debug)] #[must_use = "strategies do nothing unless used"] pub struct BoxedStrategy<T>( Arc<dyn Strategy<Value = T, Tree = BoxedVT<T>>>); /// A boxed `Strategy` trait object which is also `Sync` and /// `Send`, as produced by `Strategy::sboxed()`. /// /// Strategies of this type afford cheap shallow cloning via reference /// counting by using an `Arc` internally. #[derive(Debug)] #[must_use = "strategies do nothing unless used"] pub struct SBoxedStrategy<T>( Arc<dyn Strategy<Value = T, Tree = BoxedVT<T>> + Sync + Send>); impl<T> Clone for BoxedStrategy<T> { fn clone(&self) -> Self { BoxedStrategy(Arc::clone(&self.0)) } } impl<T> Clone for SBoxedStrategy<T> { fn clone(&self) -> Self { SBoxedStrategy(Arc::clone(&self.0)) } } impl<T: fmt::Debug> Strategy for BoxedStrategy<T> { type Tree = BoxedVT<T>; type Value = T; fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> { self.0.new_tree(runner) } // Optimization: Don't rebox the strategy. fn boxed(self) -> BoxedStrategy<Self::Value> where Self : Sized + 'static { self } } impl<T: fmt::Debug> Strategy for SBoxedStrategy<T> { type Tree = BoxedVT<T>; type Value = T; fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> { self.0.new_tree(runner) } // Optimization: Don't rebox the strategy. fn sboxed(self) -> SBoxedStrategy<Self::Value> where Self : Sized + Send + Sync + 'static { self } fn boxed(self) -> BoxedStrategy<Self::Value> where Self : Sized + 'static { BoxedStrategy(self.0) } } #[derive(Debug)] struct BoxedStrategyWrapper<T>(T); impl<T : Strategy> Strategy for BoxedStrategyWrapper<T> where T::Tree : 'static { type Tree = Box<dyn ValueTree<Value = T::Value>>; type Value = T::Value; fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> { Ok(Box::new(self.0.new_tree(runner)?)) } } //============================================================================== // Sanity checking //============================================================================== /// Options passed to `check_strategy_sanity()`. #[derive(Clone, Copy, Debug)] pub struct CheckStrategySanityOptions { /// If true (the default), require that `complicate()` return `true` at /// least once after any call to `simplify()` which itself returns once. /// /// This property is not required by contract, but many strategies are /// designed in a way that this is expected to hold. pub strict_complicate_after_simplify: bool, // Needs to be public for FRU syntax. #[allow(missing_docs)] #[doc(hidden)] pub _non_exhaustive: (), } impl Default for CheckStrategySanityOptions { fn default() -> Self { CheckStrategySanityOptions { strict_complicate_after_simplify: true, _non_exhaustive: (), } } } /// Run some tests on the given `Strategy` to ensure that it upholds the /// simplify/complicate contracts. /// /// This is used to internally test proptest, but is made generally available /// for external implementations to use as well. /// /// `options` can be passed to configure the test; if `None`, the defaults are /// used. Note that the defaults check for certain properties which are **not** /// actually required by the `Strategy` and `ValueTree` contracts; if you think /// your code is right but it fails the test, consider whether a non-default /// configuration is necessary. /// /// This can work with fallible strategies, but limits how many times it will /// retry failures. pub fn check_strategy_sanity<S : Strategy>( strategy: S, options: Option<CheckStrategySanityOptions>) where S::Tree : Clone + fmt::Debug, S::Value : cmp::PartialEq { // Like assert_eq!, but also pass if both values do not equal themselves. // This allows the test to work correctly with things like NaN. macro_rules! assert_same { ($a:expr, $b:expr, $($stuff:tt)*) => { { let a = $a; let b = $b; if a == a || b == b { assert_eq!(a, b, $($stuff)*); } } } } let options = options.unwrap_or_else(CheckStrategySanityOptions::default); let mut runner = TestRunner::default(); for _ in 0..1024 { let mut gen_tries = 0; let mut state; loop { let err = match strategy.new_tree(&mut runner) { Ok(s) => { state = s; break; }, Err(e) => e, }; gen_tries += 1; if gen_tries > 100 { panic!("Strategy passed to check_strategy_sanity failed \ to generate a value over 100 times in a row; \ last failure reason: {}", err); } } { let mut state = state.clone(); let mut count = 0; while state.simplify() || state.complicate() { count += 1; if count > 65536 { panic!("Failed to converge on any value. State:\n{:#?}", state); } } } let mut num_simplifies = 0; let mut before_simplified; loop { before_simplified = state.clone(); if !state.simplify() { break; } let mut complicated = state.clone(); let before_complicated = state.clone(); if options.strict_complicate_after_simplify { assert!(complicated.complicate(), "complicate() returned false immediately after \ simplify() returned true. internal state after \ {} calls to simplify():\n\ {:#?}\n\ simplified to:\n\ {:#?}\n\ complicated to:\n\ {:#?}", num_simplifies, before_simplified, state, complicated); } let mut prev_complicated = complicated.clone(); let mut num_complications = 0; loop { if !complicated.complicate() { break; } prev_complicated = complicated.clone(); num_complications += 1; if num_complications > 65_536 { panic!("complicate() returned true over 65536 times in a \ row; aborting due to possible infinite loop. \ If this is not an infinite loop, it may be \ necessary to reconsider how shrinking is \ implemented or use a simpler test strategy. \ Internal state:\n{:#?}", state); } } assert_same!(before_simplified.current(), complicated.current(), "Calling simplify(), then complicate() until it \ returned false, did not return to the value before \ simplify. Expected:\n\ {:#?}\n\ Actual:\n\ {:#?}\n\ Internal state after {} calls to simplify():\n\ {:#?}\n\ Internal state after another call to simplify():\n\ {:#?}\n\ Internal state after {} subsequent calls to \ complicate():\n\ {:#?}", before_simplified.current(), complicated.current(), num_simplifies, before_simplified, before_complicated, num_complications + 1, complicated); for iter in 1..16 { assert_same!(prev_complicated.current(), complicated.current(), "complicate() returned false but changed the output \ value anyway.\n\ Old value:\n\ {:#?}\n\ New value:\n\ {:#?}\n\ Old internal state:\n\ {:#?}\n\ New internal state after {} calls to complicate()\ including the :\n\ {:#?}", prev_complicated.current(), complicated.current(), prev_complicated, iter, complicated); assert!(!complicated.complicate(), "complicate() returned true after having returned \ false;\n\ Internal state before:\n{:#?}\n\ Internal state after calling complicate() {} times:\n\ {:#?}", prev_complicated, iter + 1, complicated); } num_simplifies += 1; if num_simplifies > 65_536 { panic!("simplify() returned true over 65536 times in a row, \ aborting due to possible infinite loop. If this is not \ an infinite loop, it may be necessary to reconsider \ how shrinking is implemented or use a simpler test \ strategy. Internal state:\n{:#?}", state); } } for iter in 0..16 { assert_same!(before_simplified.current(), state.current(), "simplify() returned false but changed the output \ value anyway.\n\ Old value:\n\ {:#?}\n\ New value:\n\ {:#?}\n\ Previous internal state:\n\ {:#?}\n\ New internal state after calling simplify() {} times:\n\ {:#?}", before_simplified.current(), state.current(), before_simplified, iter, state); if state.simplify() { panic!("simplify() returned true after having returned false. \ Previous internal state:\n\ {:#?}\n\ New internal state after calling simplify() {} times:\n\ {:#?}", before_simplified, iter + 1, state); } } } }