1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
//-
// Copyright 2017 Jason Lingle
//
// 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 crate::std_facade::{fmt, Arc, Vec};
use core::cmp::{max, min};
use core::u32;

#[cfg(not(feature = "std"))]
use num_traits::float::FloatCore;

use crate::num::sample_uniform;
use crate::strategy::{lazy::LazyValueTree, traits::*};
use crate::test_runner::*;

/// A **relative** `weight` of a particular `Strategy` corresponding to `T`
/// coupled with `T` itself. The weight is currently given in `u32`.
pub type W<T> = (u32, T);

/// A **relative** `weight` of a particular `Strategy` corresponding to `T`
/// coupled with `Arc<T>`. The weight is currently given in `u32`.
pub type WA<T> = (u32, Arc<T>);

/// A `Strategy` which picks from one of several delegate `Stragegy`s.
///
/// See `Strategy::prop_union()`.
#[derive(Clone, Debug)]
#[must_use = "strategies do nothing unless used"]
pub struct Union<T: Strategy> {
    // In principle T could be any `Strategy + Clone`, but that isn't possible
    // for BC reasons with the 0.9 series.
    options: Vec<WA<T>>,
}

impl<T: Strategy> Union<T> {
    /// Create a strategy which selects uniformly from the given delegate
    /// strategies.
    ///
    /// When shrinking, after maximal simplification of the chosen element, the
    /// strategy will move to earlier options and continue simplification with
    /// those.
    ///
    /// ## Panics
    ///
    /// Panics if `options` is empty.
    pub fn new(options: impl IntoIterator<Item = T>) -> Self {
        let options: Vec<WA<T>> =
            options.into_iter().map(|v| (1, Arc::new(v))).collect();
        assert!(!options.is_empty());
        Self { options }
    }

    pub(crate) fn try_new<E>(
        it: impl Iterator<Item = Result<T, E>>,
    ) -> Result<Self, E> {
        let options: Vec<WA<T>> = it
            .map(|r| r.map(|v| (1, Arc::new(v))))
            .collect::<Result<_, _>>()?;

        assert!(!options.is_empty());
        Ok(Self { options })
    }

    /// Create a strategy which selects from the given delegate strategies.
    ///
    /// Each strategy is assigned a non-zero weight which determines how
    /// frequently that strategy is chosen. For example, a strategy with a
    /// weight of 2 will be chosen twice as frequently as one with a weight of
    /// 1\.
    ///
    /// ## Panics
    ///
    /// Panics if `options` is empty or any element has a weight of 0.
    ///
    /// Panics if the sum of the weights overflows a `u32`.
    pub fn new_weighted(options: Vec<W<T>>) -> Self {
        assert!(!options.is_empty());
        assert!(
            !options.iter().any(|&(w, _)| 0 == w),
            "Union option has a weight of 0"
        );
        assert!(
            options.iter().map(|&(w, _)| u64::from(w)).sum::<u64>()
                <= u64::from(u32::MAX),
            "Union weights overflow u32"
        );
        let options =
            options.into_iter().map(|(w, v)| (w, Arc::new(v))).collect();
        Self { options }
    }

    /// Add `other` as an additional alternate strategy with weight 1.
    pub fn or(mut self, other: T) -> Self {
        self.options.push((1, Arc::new(other)));
        self
    }
}

fn pick_weighted<I: Iterator<Item = u32>>(
    runner: &mut TestRunner,
    weights1: I,
    weights2: I,
) -> usize {
    let sum = weights1.map(u64::from).sum();
    let weighted_pick = sample_uniform(runner, 0..sum);
    weights2
        .scan(0u64, |state, w| {
            *state += u64::from(w);
            Some(*state)
        })
        .filter(|&v| v <= weighted_pick)
        .count()
}

impl<T: Strategy> Strategy for Union<T> {
    type Tree = UnionValueTree<T>;
    type Value = T::Value;

    fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
        fn extract_weight<V>(&(w, _): &WA<V>) -> u32 {
            w
        }

        let pick = pick_weighted(
            runner,
            self.options.iter().map(extract_weight::<T>),
            self.options.iter().map(extract_weight::<T>),
        );

        let mut options = Vec::with_capacity(pick);

        // Delay initialization for all options less than pick.
        for option in &self.options[0..pick] {
            options.push(LazyValueTree::new(Arc::clone(&option.1), runner));
        }

        // Initialize the tree at pick so at least one value is available. Note
        // that if generation for the value at pick fails, the entire strategy
        // will fail. This seems like the right call.
        options.push(LazyValueTree::new_initialized(
            self.options[pick].1.new_tree(runner)?,
        ));

        Ok(UnionValueTree {
            options,
            pick,
            min_pick: 0,
            prev_pick: None,
        })
    }
}

macro_rules! access_vec {
    ([$($muta:tt)*] $dst:ident = $this:expr, $ix:expr, $body:block) => {{
        let $dst = &$($muta)* $this.options[$ix];
        $body
    }}
}

/// `ValueTree` corresponding to `Union`.
pub struct UnionValueTree<T: Strategy> {
    options: Vec<LazyValueTree<T>>,
    // This struct maintains the invariant that between function calls,
    // `pick` and `prev_pick` (if Some) always point to initialized
    // trees.
    pick: usize,
    min_pick: usize,
    prev_pick: Option<usize>,
}

macro_rules! lazy_union_value_tree_body {
    ($typ:ty, $access:ident) => {
        type Value = $typ;

        fn current(&self) -> Self::Value {
            $access!([] opt = self, self.pick, {
                opt.as_inner().unwrap_or_else(||
                    panic!(
                        "value tree at self.pick = {} must be initialized",
                        self.pick,
                    )
                ).current()
            })
        }

        fn simplify(&mut self) -> bool {
            let orig_pick = self.pick;
            if $access!([mut] opt = self, orig_pick, {
                opt.as_inner_mut().unwrap_or_else(||
                    panic!(
                        "value tree at self.pick = {} must be initialized",
                        orig_pick,
                    )
                ).simplify()
            }) {
                self.prev_pick = None;
                return true;
            }

            assert!(
                self.pick >= self.min_pick,
                "self.pick = {} should never go below self.min_pick = {}",
                self.pick,
                self.min_pick,
            );
            if self.pick == self.min_pick {
                // No more simplification to be done.
                return false;
            }

            // self.prev_pick is always a valid pick.
            self.prev_pick = Some(self.pick);

            let mut next_pick = self.pick;
            while next_pick > self.min_pick {
                next_pick -= 1;
                let initialized = $access!([mut] opt = self, next_pick, {
                    opt.maybe_init();
                    opt.is_initialized()
                });
                if initialized {
                    // next_pick was correctly initialized above.
                    self.pick = next_pick;
                    return true;
                }
            }

            false
        }

        fn complicate(&mut self) -> bool {
            if let Some(pick) = self.prev_pick {
                // simplify() ensures that the previous pick was initialized.
                self.pick = pick;
                self.min_pick = pick;
                self.prev_pick = None;
                true
            } else {
                let pick = self.pick;
                $access!([mut] opt = self, pick, {
                    opt.as_inner_mut().unwrap_or_else(||
                        panic!(
                            "value tree at self.pick = {} must be initialized",
                            pick,
                        )
                    ).complicate()
                })
            }
        }
    }
}

impl<T: Strategy> ValueTree for UnionValueTree<T> {
    lazy_union_value_tree_body!(T::Value, access_vec);
}

impl<T: Strategy> Clone for UnionValueTree<T>
where
    T::Tree: Clone,
{
    fn clone(&self) -> Self {
        Self {
            options: self.options.clone(),
            pick: self.pick,
            min_pick: self.min_pick,
            prev_pick: self.prev_pick,
        }
    }
}

impl<T: Strategy> fmt::Debug for UnionValueTree<T>
where
    T::Tree: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("UnionValueTree")
            .field("options", &self.options)
            .field("pick", &self.pick)
            .field("min_pick", &self.min_pick)
            .field("prev_pick", &self.prev_pick)
            .finish()
    }
}

macro_rules! def_access_tuple {
    ($b:tt $name:ident, $($n:tt)*) => {
        macro_rules! $name {
            ([$b($b muta:tt)*] $b dst:ident = $b this:expr,
             $b ix:expr, $b body:block) => {
                match $b ix {
                    0 => {
                        let $b dst = &$b($b muta)* $b this.options.0;
                        $b body
                    },
                    $(
                        $n => {
                            if let Some(ref $b($b muta)* $b dst) =
                                $b this.options.$n
                            {
                                $b body
                            } else {
                                panic!("TupleUnion tried to access \
                                        uninitialised slot {}", $n)
                            }
                        },
                    )*
                    _ => panic!("TupleUnion tried to access out-of-range \
                                 slot {}", $b ix),
                }
            }
        }
    }
}

def_access_tuple!($ access_tuple2, 1);
def_access_tuple!($ access_tuple3, 1 2);
def_access_tuple!($ access_tuple4, 1 2 3);
def_access_tuple!($ access_tuple5, 1 2 3 4);
def_access_tuple!($ access_tuple6, 1 2 3 4 5);
def_access_tuple!($ access_tuple7, 1 2 3 4 5 6);
def_access_tuple!($ access_tuple8, 1 2 3 4 5 6 7);
def_access_tuple!($ access_tuple9, 1 2 3 4 5 6 7 8);
def_access_tuple!($ access_tupleA, 1 2 3 4 5 6 7 8 9);

/// Similar to `Union`, but internally uses a tuple to hold the strategies.
///
/// This allows better performance than vanilla `Union` since one does not need
/// to resort to boxing and dynamic dispatch to handle heterogeneous
/// strategies.
///
/// The difference between this and `TupleUnion` is that with this, value trees
/// for variants that aren't picked at first are generated lazily.
#[must_use = "strategies do nothing unless used"]
#[derive(Clone, Copy, Debug)]
pub struct TupleUnion<T>(T);

impl<T> TupleUnion<T> {
    /// Wrap `tuple` in a `TupleUnion`.
    ///
    /// The struct definition allows any `T` for `tuple`, but to be useful, it
    /// must be a 2- to 10-tuple of `(u32, Arc<impl Strategy>)` pairs where all
    /// strategies ultimately produce the same value. Each `u32` indicates the
    /// relative weight of its corresponding strategy.
    /// You may use `WA<S>` as an alias for `(u32, Arc<S>)`.
    ///
    /// Using this constructor directly is discouraged; prefer to use
    /// `prop_oneof!` since it is generally clearer.
    pub fn new(tuple: T) -> Self {
        TupleUnion(tuple)
    }
}

macro_rules! tuple_union {
    ($($gen:ident $ix:tt)*) => {
        impl<A : Strategy, $($gen: Strategy<Value = A::Value>),*>
        Strategy for TupleUnion<(WA<A>, $(WA<$gen>),*)> {
            type Tree = TupleUnionValueTree<
                (LazyValueTree<A>, $(Option<LazyValueTree<$gen>>),*)>;
            type Value = A::Value;

            fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
                let weights = [((self.0).0).0, $(((self.0).$ix).0),*];
                let pick = pick_weighted(runner, weights.iter().cloned(),
                                         weights.iter().cloned());

                Ok(TupleUnionValueTree {
                    options: (
                        if 0 == pick {
                            LazyValueTree::new_initialized(
                                ((self.0).0).1.new_tree(runner)?)
                        } else {
                            LazyValueTree::new(
                                Arc::clone(&((self.0).0).1), runner)
                        },
                        $(
                        if $ix == pick {
                            Some(LazyValueTree::new_initialized(
                                 ((self.0).$ix).1.new_tree(runner)?))
                        } else if $ix < pick {
                            Some(LazyValueTree::new(
                                    Arc::clone(&((self.0).$ix).1), runner))
                        } else {
                            None
                        }),*),
                    pick: pick,
                    min_pick: 0,
                    prev_pick: None,
                })
            }
        }
    }
}

tuple_union!(B 1);
tuple_union!(B 1 C 2);
tuple_union!(B 1 C 2 D 3);
tuple_union!(B 1 C 2 D 3 E 4);
tuple_union!(B 1 C 2 D 3 E 4 F 5);
tuple_union!(B 1 C 2 D 3 E 4 F 5 G 6);
tuple_union!(B 1 C 2 D 3 E 4 F 5 G 6 H 7);
tuple_union!(B 1 C 2 D 3 E 4 F 5 G 6 H 7 I 8);
tuple_union!(B 1 C 2 D 3 E 4 F 5 G 6 H 7 I 8 J 9);

/// `ValueTree` type produced by `TupleUnion`.
#[derive(Clone, Copy, Debug)]
pub struct TupleUnionValueTree<T> {
    options: T,
    pick: usize,
    min_pick: usize,
    prev_pick: Option<usize>,
}

macro_rules! value_tree_tuple {
    ($access:ident, $($gen:ident)*) => {
        impl<A : Strategy, $($gen: Strategy<Value = A::Value>),*> ValueTree
        for TupleUnionValueTree<
            (LazyValueTree<A>, $(Option<LazyValueTree<$gen>>),*)
        > {
            lazy_union_value_tree_body!(A::Value, $access);
        }
    }
}

value_tree_tuple!(access_tuple2, B);
value_tree_tuple!(access_tuple3, B C);
value_tree_tuple!(access_tuple4, B C D);
value_tree_tuple!(access_tuple5, B C D E);
value_tree_tuple!(access_tuple6, B C D E F);
value_tree_tuple!(access_tuple7, B C D E F G);
value_tree_tuple!(access_tuple8, B C D E F G H);
value_tree_tuple!(access_tuple9, B C D E F G H I);
value_tree_tuple!(access_tupleA, B C D E F G H I J);

const WEIGHT_BASE: u32 = 0x8000_0000;

/// Convert a floating-point weight in the range (0.0,1.0) to a pair of weights
/// that can be used with `Union` and similar.
///
/// The first return value is the weight corresponding to `f`; the second
/// return value is the weight corresponding to `1.0 - f`.
///
/// This call does not make any guarantees as to what range of weights it may
/// produce, except that adding the two return values will never overflow a
/// `u32`. As such, it is generally not meaningful to combine any other weights
/// with the two returned.
///
/// ## Panics
///
/// Panics if `f` is not a real number between 0.0 and 1.0, both exclusive.
pub fn float_to_weight(f: f64) -> (u32, u32) {
    assert!(f > 0.0 && f < 1.0, "Invalid probability: {}", f);

    // Clamp to 1..WEIGHT_BASE-1 so that we never produce a weight of 0.
    let pos = max(
        1,
        min(WEIGHT_BASE - 1, (f * f64::from(WEIGHT_BASE)).round() as u32),
    );
    let neg = WEIGHT_BASE - pos;

    (pos, neg)
}

#[cfg(test)]
mod test {
    use super::*;
    use crate::strategy::just::Just;

    // FIXME(2018-06-01): figure out a way to run this test on no_std.
    // The problem is that the default seed is fixed and does not produce
    // enough passed tests. We need some universal source of non-determinism
    // for the seed, which is unlikely.
    #[cfg(feature = "std")]
    #[test]
    fn test_union() {
        let input = (10u32..20u32).prop_union(30u32..40u32);
        // Expect that 25% of cases pass (left input happens to be < 15, and
        // left is chosen as initial value). Of the 75% that fail, 50% should
        // converge to 15 and 50% to 30 (the latter because the left is beneath
        // the passing threshold).
        let mut passed = 0;
        let mut converged_low = 0;
        let mut converged_high = 0;
        let mut runner = TestRunner::deterministic();
        for _ in 0..256 {
            let case = input.new_tree(&mut runner).unwrap();
            let result = runner.run_one(case, |v| {
                prop_assert!(v < 15);
                Ok(())
            });

            match result {
                Ok(true) => passed += 1,
                Err(TestError::Fail(_, 15)) => converged_low += 1,
                Err(TestError::Fail(_, 30)) => converged_high += 1,
                e => panic!("Unexpected result: {:?}", e),
            }
        }

        assert!(passed >= 32 && passed <= 96, "Bad passed count: {}", passed);
        assert!(
            converged_low >= 32 && converged_low <= 160,
            "Bad converged_low count: {}",
            converged_low
        );
        assert!(
            converged_high >= 32 && converged_high <= 160,
            "Bad converged_high count: {}",
            converged_high
        );
    }

    #[test]
    fn test_union_weighted() {
        let input = Union::new_weighted(vec![
            (1, Just(0usize)),
            (2, Just(1usize)),
            (1, Just(2usize)),
        ]);

        let mut counts = [0, 0, 0];
        let mut runner = TestRunner::deterministic();
        for _ in 0..65536 {
            counts[input.new_tree(&mut runner).unwrap().current()] += 1;
        }

        println!("{:?}", counts);
        assert!(counts[0] > 0);
        assert!(counts[2] > 0);
        assert!(counts[1] > counts[0] * 3 / 2);
        assert!(counts[1] > counts[2] * 3 / 2);
    }

    #[test]
    fn test_union_sanity() {
        check_strategy_sanity(
            Union::new_weighted(vec![
                (1, 0i32..100),
                (2, 200i32..300),
                (1, 400i32..500),
            ]),
            None,
        );
    }

    // FIXME(2018-06-01): See note on `test_union`.
    #[cfg(feature = "std")]
    #[test]
    fn test_tuple_union() {
        let input = TupleUnion::new((
            (1, Arc::new(10u32..20u32)),
            (1, Arc::new(30u32..40u32)),
        ));
        // Expect that 25% of cases pass (left input happens to be < 15, and
        // left is chosen as initial value). Of the 75% that fail, 50% should
        // converge to 15 and 50% to 30 (the latter because the left is beneath
        // the passing threshold).
        let mut passed = 0;
        let mut converged_low = 0;
        let mut converged_high = 0;
        let mut runner = TestRunner::deterministic();
        for _ in 0..256 {
            let case = input.new_tree(&mut runner).unwrap();
            let result = runner.run_one(case, |v| {
                prop_assert!(v < 15);
                Ok(())
            });

            match result {
                Ok(true) => passed += 1,
                Err(TestError::Fail(_, 15)) => converged_low += 1,
                Err(TestError::Fail(_, 30)) => converged_high += 1,
                e => panic!("Unexpected result: {:?}", e),
            }
        }

        assert!(passed >= 32 && passed <= 96, "Bad passed count: {}", passed);
        assert!(
            converged_low >= 32 && converged_low <= 160,
            "Bad converged_low count: {}",
            converged_low
        );
        assert!(
            converged_high >= 32 && converged_high <= 160,
            "Bad converged_high count: {}",
            converged_high
        );
    }

    #[test]
    fn test_tuple_union_weighting() {
        let input = TupleUnion::new((
            (1, Arc::new(Just(0usize))),
            (2, Arc::new(Just(1usize))),
            (1, Arc::new(Just(2usize))),
        ));

        let mut counts = [0, 0, 0];
        let mut runner = TestRunner::deterministic();
        for _ in 0..65536 {
            counts[input.new_tree(&mut runner).unwrap().current()] += 1;
        }

        println!("{:?}", counts);
        assert!(counts[0] > 0);
        assert!(counts[2] > 0);
        assert!(counts[1] > counts[0] * 3 / 2);
        assert!(counts[1] > counts[2] * 3 / 2);
    }

    #[test]
    fn test_tuple_union_all_sizes() {
        let mut runner = TestRunner::deterministic();
        let r = Arc::new(1i32..10);

        macro_rules! test {
            ($($part:expr),*) => {{
                let input = TupleUnion::new((
                    $((1, $part.clone())),*,
                    (1, Arc::new(Just(0i32)))
                ));

                let mut pass = false;
                for _ in 0..1024 {
                    if 0 == input.new_tree(&mut runner).unwrap().current() {
                        pass = true;
                        break;
                    }
                }

                assert!(pass);
            }}
        }

        test!(r); // 2
        test!(r, r); // 3
        test!(r, r, r); // 4
        test!(r, r, r, r); // 5
        test!(r, r, r, r, r); // 6
        test!(r, r, r, r, r, r); // 7
        test!(r, r, r, r, r, r, r); // 8
        test!(r, r, r, r, r, r, r, r); // 9
        test!(r, r, r, r, r, r, r, r, r); // 10
    }

    #[test]
    fn test_tuple_union_sanity() {
        check_strategy_sanity(
            TupleUnion::new((
                (1, Arc::new(0i32..100i32)),
                (1, Arc::new(200i32..1000i32)),
                (1, Arc::new(2000i32..3000i32)),
            )),
            None,
        );
    }

    /// Test that unions work even if local filtering causes errors.
    #[test]
    fn test_filter_union_sanity() {
        let filter_strategy = (0u32..256).prop_filter("!%5", |&v| 0 != v % 5);
        check_strategy_sanity(
            Union::new(vec![filter_strategy; 8]),
            Some(filter_sanity_options()),
        );
    }

    /// Test that tuple unions work even if local filtering causes errors.
    #[test]
    fn test_filter_tuple_union_sanity() {
        let filter_strategy = (0u32..256).prop_filter("!%5", |&v| 0 != v % 5);
        check_strategy_sanity(
            TupleUnion::new((
                (1, Arc::new(filter_strategy.clone())),
                (1, Arc::new(filter_strategy.clone())),
                (1, Arc::new(filter_strategy.clone())),
                (1, Arc::new(filter_strategy.clone())),
            )),
            Some(filter_sanity_options()),
        );
    }

    fn filter_sanity_options() -> CheckStrategySanityOptions {
        CheckStrategySanityOptions {
            // Due to internal rejection sampling, `simplify()` can
            // converge back to what `complicate()` would do.
            strict_complicate_after_simplify: false,
            // Make failed filters return errors to test edge cases.
            error_on_local_rejects: true,
            ..CheckStrategySanityOptions::default()
        }
    }
}