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
use std::cmp;
use std::env;
use std::fmt::Debug;
use std::panic;

use crate::{
    tester::Status::{Discard, Fail, Pass},
    Arbitrary, Gen,
};

/// The main QuickCheck type for setting configuration and running QuickCheck.
pub struct QuickCheck {
    tests: u64,
    max_tests: u64,
    min_tests_passed: u64,
    gen: Gen,
}

fn qc_tests() -> u64 {
    let default = 100;
    match env::var("QUICKCHECK_TESTS") {
        Ok(val) => val.parse().unwrap_or(default),
        Err(_) => default,
    }
}

fn qc_max_tests() -> u64 {
    let default = 10_000;
    match env::var("QUICKCHECK_MAX_TESTS") {
        Ok(val) => val.parse().unwrap_or(default),
        Err(_) => default,
    }
}

fn qc_gen_size() -> usize {
    let default = 100;
    match env::var("QUICKCHECK_GENERATOR_SIZE") {
        Ok(val) => val.parse().unwrap_or(default),
        Err(_) => default,
    }
}

fn qc_min_tests_passed() -> u64 {
    let default = 0;
    match env::var("QUICKCHECK_MIN_TESTS_PASSED") {
        Ok(val) => val.parse().unwrap_or(default),
        Err(_) => default,
    }
}

impl QuickCheck {
    /// Creates a new QuickCheck value.
    ///
    /// This can be used to run QuickCheck on things that implement `Testable`.
    /// You may also adjust the configuration, such as the number of tests to
    /// run.
    ///
    /// By default, the maximum number of passed tests is set to `100`, the max
    /// number of overall tests is set to `10000` and the generator is created
    /// with a size of `100`.
    pub fn new() -> QuickCheck {
        let gen = Gen::new(qc_gen_size());
        let tests = qc_tests();
        let max_tests = cmp::max(tests, qc_max_tests());
        let min_tests_passed = qc_min_tests_passed();

        QuickCheck { tests, max_tests, min_tests_passed, gen }
    }

    /// Set the random number generator to be used by QuickCheck.
    pub fn gen(self, gen: Gen) -> QuickCheck {
        QuickCheck { gen, ..self }
    }

    /// Set the number of tests to run.
    ///
    /// This actually refers to the maximum number of *passed* tests that
    /// can occur. Namely, if a test causes a failure, future testing on that
    /// property stops. Additionally, if tests are discarded, there may be
    /// fewer than `tests` passed.
    pub fn tests(mut self, tests: u64) -> QuickCheck {
        self.tests = tests;
        self
    }

    /// Set the maximum number of tests to run.
    ///
    /// The number of invocations of a property will never exceed this number.
    /// This is necessary to cap the number of tests because QuickCheck
    /// properties can discard tests.
    pub fn max_tests(mut self, max_tests: u64) -> QuickCheck {
        self.max_tests = max_tests;
        self
    }

    /// Set the minimum number of tests that needs to pass.
    ///
    /// This actually refers to the minimum number of *valid* *passed* tests
    /// that needs to pass for the property to be considered successful.
    pub fn min_tests_passed(mut self, min_tests_passed: u64) -> QuickCheck {
        self.min_tests_passed = min_tests_passed;
        self
    }

    /// Tests a property and returns the result.
    ///
    /// The result returned is either the number of tests passed or a witness
    /// of failure.
    ///
    /// (If you're using Rust's unit testing infrastructure, then you'll
    /// want to use the `quickcheck` method, which will `panic!` on failure.)
    pub fn quicktest<A>(&mut self, f: A) -> Result<u64, TestResult>
    where
        A: Testable,
    {
        let mut n_tests_passed = 0;
        for _ in 0..self.max_tests {
            if n_tests_passed >= self.tests {
                break;
            }
            match f.result(&mut self.gen) {
                TestResult { status: Pass, .. } => n_tests_passed += 1,
                TestResult { status: Discard, .. } => continue,
                r @ TestResult { status: Fail, .. } => return Err(r),
            }
        }
        Ok(n_tests_passed)
    }

    /// Tests a property and calls `panic!` on failure.
    ///
    /// The `panic!` message will include a (hopefully) minimal witness of
    /// failure.
    ///
    /// It is appropriate to use this method with Rust's unit testing
    /// infrastructure.
    ///
    /// Note that if the environment variable `RUST_LOG` is set to enable
    /// `info` level log messages for the `quickcheck` crate, then this will
    /// include output on how many QuickCheck tests were passed.
    ///
    /// # Example
    ///
    /// ```rust
    /// use quickcheck::QuickCheck;
    ///
    /// fn prop_reverse_reverse() {
    ///     fn revrev(xs: Vec<usize>) -> bool {
    ///         let rev: Vec<_> = xs.clone().into_iter().rev().collect();
    ///         let revrev: Vec<_> = rev.into_iter().rev().collect();
    ///         xs == revrev
    ///     }
    ///     QuickCheck::new().quickcheck(revrev as fn(Vec<usize>) -> bool);
    /// }
    /// ```
    pub fn quickcheck<A>(&mut self, f: A)
    where
        A: Testable,
    {
        // Ignore log init failures, implying it has already been done.
        let _ = crate::env_logger_init();

        let n_tests_passed = match self.quicktest(f) {
            Ok(n_tests_passed) => n_tests_passed,
            Err(result) => panic!(result.failed_msg()),
        };

        if n_tests_passed >= self.min_tests_passed {
            info!("(Passed {} QuickCheck tests.)", n_tests_passed)
        } else {
            panic!(
                "(Unable to generate enough tests, {} not discarded.)",
                n_tests_passed
            )
        }
    }
}

/// Convenience function for running QuickCheck.
///
/// This is an alias for `QuickCheck::new().quickcheck(f)`.
pub fn quickcheck<A: Testable>(f: A) {
    QuickCheck::new().quickcheck(f)
}

/// Describes the status of a single instance of a test.
///
/// All testable things must be capable of producing a `TestResult`.
#[derive(Clone, Debug)]
pub struct TestResult {
    status: Status,
    arguments: Vec<String>,
    err: Option<String>,
}

/// Whether a test has passed, failed or been discarded.
#[derive(Clone, Debug)]
enum Status {
    Pass,
    Fail,
    Discard,
}

impl TestResult {
    /// Produces a test result that indicates the current test has passed.
    pub fn passed() -> TestResult {
        TestResult::from_bool(true)
    }

    /// Produces a test result that indicates the current test has failed.
    pub fn failed() -> TestResult {
        TestResult::from_bool(false)
    }

    /// Produces a test result that indicates failure from a runtime error.
    pub fn error<S: Into<String>>(msg: S) -> TestResult {
        let mut r = TestResult::from_bool(false);
        r.err = Some(msg.into());
        r
    }

    /// Produces a test result that instructs `quickcheck` to ignore it.
    /// This is useful for restricting the domain of your properties.
    /// When a test is discarded, `quickcheck` will replace it with a
    /// fresh one (up to a certain limit).
    pub fn discard() -> TestResult {
        TestResult { status: Discard, arguments: vec![], err: None }
    }

    /// Converts a `bool` to a `TestResult`. A `true` value indicates that
    /// the test has passed and a `false` value indicates that the test
    /// has failed.
    pub fn from_bool(b: bool) -> TestResult {
        TestResult {
            status: if b { Pass } else { Fail },
            arguments: vec![],
            err: None,
        }
    }

    /// Tests if a "procedure" fails when executed. The test passes only if
    /// `f` generates a task failure during its execution.
    pub fn must_fail<T, F>(f: F) -> TestResult
    where
        F: FnOnce() -> T,
        F: 'static,
        T: 'static,
    {
        let f = panic::AssertUnwindSafe(f);
        TestResult::from_bool(panic::catch_unwind(f).is_err())
    }

    /// Returns `true` if and only if this test result describes a failing
    /// test.
    pub fn is_failure(&self) -> bool {
        match self.status {
            Fail => true,
            Pass | Discard => false,
        }
    }

    /// Returns `true` if and only if this test result describes a failing
    /// test as a result of a run time error.
    pub fn is_error(&self) -> bool {
        self.is_failure() && self.err.is_some()
    }

    fn failed_msg(&self) -> String {
        match self.err {
            None => format!(
                "[quickcheck] TEST FAILED. Arguments: ({})",
                self.arguments.join(", ")
            ),
            Some(ref err) => format!(
                "[quickcheck] TEST FAILED (runtime error). \
                 Arguments: ({})\nError: {}",
                self.arguments.join(", "),
                err
            ),
        }
    }
}

/// `Testable` describes types (e.g., a function) whose values can be
/// tested.
///
/// Anything that can be tested must be capable of producing a `TestResult`
/// given a random number generator. This is trivial for types like `bool`,
/// which are just converted to either a passing or failing test result.
///
/// For functions, an implementation must generate random arguments
/// and potentially shrink those arguments if they produce a failure.
///
/// It's unlikely that you'll have to implement this trait yourself.
pub trait Testable: 'static {
    fn result(&self, _: &mut Gen) -> TestResult;
}

impl Testable for bool {
    fn result(&self, _: &mut Gen) -> TestResult {
        TestResult::from_bool(*self)
    }
}

impl Testable for () {
    fn result(&self, _: &mut Gen) -> TestResult {
        TestResult::passed()
    }
}

impl Testable for TestResult {
    fn result(&self, _: &mut Gen) -> TestResult {
        self.clone()
    }
}

impl<A, E> Testable for Result<A, E>
where
    A: Testable,
    E: Debug + 'static,
{
    fn result(&self, g: &mut Gen) -> TestResult {
        match *self {
            Ok(ref r) => r.result(g),
            Err(ref err) => TestResult::error(format!("{:?}", err)),
        }
    }
}

/// Return a vector of the debug formatting of each item in `args`
fn debug_reprs(args: &[&dyn Debug]) -> Vec<String> {
    args.iter().map(|x| format!("{:?}", x)).collect()
}

macro_rules! testable_fn {
    ($($name: ident),*) => {

impl<T: Testable,
     $($name: Arbitrary + Debug),*> Testable for fn($($name),*) -> T {
    #[allow(non_snake_case)]
    fn result(&self, g: &mut Gen) -> TestResult {
        fn shrink_failure<T: Testable, $($name: Arbitrary + Debug),*>(
            g: &mut Gen,
            self_: fn($($name),*) -> T,
            a: ($($name,)*),
        ) -> Option<TestResult> {
            for t in a.shrink() {
                let ($($name,)*) = t.clone();
                let mut r_new = safe(move || {self_($($name),*)}).result(g);
                if r_new.is_failure() {
                    {
                        let ($(ref $name,)*) : ($($name,)*) = t;
                        r_new.arguments = debug_reprs(&[$($name),*]);
                    }

                    // The shrunk value *does* witness a failure, so keep
                    // trying to shrink it.
                    let shrunk = shrink_failure(g, self_, t);

                    // If we couldn't witness a failure on any shrunk value,
                    // then return the failure we already have.
                    return Some(shrunk.unwrap_or(r_new))
                }
            }
            None
        }

        let self_ = *self;
        let a: ($($name,)*) = Arbitrary::arbitrary(g);
        let ( $($name,)* ) = a.clone();
        let mut r = safe(move || {self_($($name),*)}).result(g);

        {
            let ( $(ref $name,)* ) = a;
            r.arguments = debug_reprs(&[$($name),*]);
        }
        match r.status {
            Pass|Discard => r,
            Fail => {
                shrink_failure(g, self_, a).unwrap_or(r)
            }
        }
    }
}}}

testable_fn!();
testable_fn!(A);
testable_fn!(A, B);
testable_fn!(A, B, C);
testable_fn!(A, B, C, D);
testable_fn!(A, B, C, D, E);
testable_fn!(A, B, C, D, E, F);
testable_fn!(A, B, C, D, E, F, G);
testable_fn!(A, B, C, D, E, F, G, H);

fn safe<T, F>(fun: F) -> Result<T, String>
where
    F: FnOnce() -> T,
    F: 'static,
    T: 'static,
{
    panic::catch_unwind(panic::AssertUnwindSafe(fun)).map_err(|any_err| {
        // Extract common types of panic payload:
        // panic and assert produce &str or String
        if let Some(&s) = any_err.downcast_ref::<&str>() {
            s.to_owned()
        } else if let Some(s) = any_err.downcast_ref::<String>() {
            s.to_owned()
        } else {
            "UNABLE TO SHOW RESULT OF PANIC.".to_owned()
        }
    })
}

/// Convenient aliases.
trait AShow: Arbitrary + Debug {}
impl<A: Arbitrary + Debug> AShow for A {}

#[cfg(test)]
mod test {
    use crate::{Gen, QuickCheck};

    #[test]
    fn shrinking_regression_issue_126() {
        fn thetest(vals: Vec<bool>) -> bool {
            vals.iter().filter(|&v| *v).count() < 2
        }
        let failing_case = QuickCheck::new()
            .quicktest(thetest as fn(vals: Vec<bool>) -> bool)
            .unwrap_err();
        let expected_argument = format!("{:?}", [true, true]);
        assert_eq!(failing_case.arguments, vec![expected_argument]);
    }

    #[test]
    fn size_for_small_types_issue_143() {
        fn t(_: i8) -> bool {
            true
        }
        QuickCheck::new().gen(Gen::new(129)).quickcheck(t as fn(i8) -> bool);
    }

    #[test]
    fn regression_signed_shrinker_panic() {
        fn foo_can_shrink(v: i8) -> bool {
            let _ = crate::Arbitrary::shrink(&v).take(100).count();
            true
        }
        crate::quickcheck(foo_can_shrink as fn(i8) -> bool);
    }
}