vendor/proptest-1.0.0/src/char.rs - toolchain/rustc - Git at Google

 //-
 // 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.

 //! Strategies for generating `char` values.
 //!
 //! Unlike most strategies in Proptest, character generation is by default
 //! biased to particular values known to be difficult to handle in various
 //! circumstances.
 //!
 //! The main things of interest are `any()` to generate truly arbitrary
 //! characters, and `range()` and `ranges()` to select characters from
 //! inclusive ranges.

 use crate::std_facade::Cow;
 use core::ops::RangeInclusive;

 use rand::Rng;

 use crate::num;
 use crate::strategy::*;
 use crate::test_runner::*;

 /// An inclusive char range from fst to snd.
 type CharRange = RangeInclusive<char>;

 /// A default set of characters to consider as "special" during character
 /// generation.
 ///
 /// Most of the characters here were chosen specifically because they are
 /// difficult to handle in particular contexts.
 pub const DEFAULT_SPECIAL_CHARS: &[char] = &[
     // Things to give shell scripts and filesystem logic difficulties
     '/', '\\', '$', '.', '*', '{', '\'', '"', '`', ':',
     // Characters with special significance in URLs and elsewhere
     '?', '%', '=', '&', '<',
     // Interesting ASCII control characters
     // NUL, HT,   CR,   LF,   VT      ESC     DEL
     '\x00', '\t', '\r', '\n', '\x0B', '\x1B', '\x7F',
     // ¥ both to test simple Unicode handling and because it has interesting
     // properties on MS Shift-JIS systems.
     '¥', // No non-Unicode encoding has both ¥ and Ѩ
     'Ѩ',
     // In UTF-8, Ⱥ increases in length from 2 to 3 bytes when lowercased
     'Ⱥ',
     // More Unicode edge-cases: BOM, replacement character, RTL override, and non-BMP
     '\u{FEFF}', '\u{FFFD}', '\u{202E}', '🕴',
 ];

 /// A default sequence of ranges used preferentially when generating random
 /// characters.
 pub const DEFAULT_PREFERRED_RANGES: &[CharRange] = &[
     // ASCII printable
     ' '..='~',
     ' '..='~',
     ' '..='~',
     ' '..='~',
     ' '..='~',
     // Latin-1
     '\u{0040}'..='\u{00ff}',
 ];

 /// Selects a random character the way `CharStrategy` does.
 ///
 /// If `special` is non-empty, there is a 50% chance that a character from this
 /// array is chosen randomly, and will be returned if that character falls
 /// within `ranges`.
 ///
 /// If `preferred` is non-empty, there is a 50% chance that any generation
 /// which gets past the `special` step picks a random element from this list,
 /// then a random character from within that range (both endpoints inclusive).
 /// That character will be returned if it falls within `ranges`.
 ///
 /// In all other cases, an element is picked randomly from `ranges` and a
 /// random character within the range (both endpoints inclusive) is chosen and
 /// returned.
 ///
 /// Notice that in all cases, `ranges` completely defines the set of characters
 /// that can possibly be defined.
 ///
 /// It is legal for ranges in all cases to contain non-characters.
 ///
 /// Both `preferred` and `ranges` bias selection towards characters in smaller
 /// ranges. This is deliberate. `preferred` is usually tuned to select
 /// particular characters anyway. `ranges` is usually derived from some
 /// external property, and the fact that a range is small often means it is
 /// more interesting.
 pub fn select_char(
     rnd: &mut impl Rng,
     special: &[char],
     preferred: &[CharRange],
     ranges: &[CharRange],
 ) -> char {
     let (base, offset) = select_range_index(rnd, special, preferred, ranges);
     ::core::char::from_u32(base + offset).expect("bad character selected")
 }

 fn select_range_index(
     rnd: &mut impl Rng,
     special: &[char],
     preferred: &[CharRange],
     ranges: &[CharRange],
 ) -> (u32, u32) {
     fn in_range(ranges: &[CharRange], ch: char) -> Option<(u32, u32)> {
         ranges
             .iter()
             .find(|r| ch >= *r.start() && ch <= *r.end())
             .map(|r| (*r.start() as u32, ch as u32 - *r.start() as u32))
     }

     if !special.is_empty() && rnd.gen() {
         let s = special[rnd.gen_range(0..special.len())];
         if let Some(ret) = in_range(ranges, s) {
             return ret;
         }
     }

     if !preferred.is_empty() && rnd.gen() {
         let range = preferred[rnd.gen_range(0..preferred.len())].clone();
         if let Some(ch) = ::core::char::from_u32(
             rnd.gen_range(*range.start() as u32..*range.end() as u32 + 1),
         ) {
             if let Some(ret) = in_range(ranges, ch) {
                 return ret;
             }
         }
     }

     for _ in 0..65_536 {
         let range = ranges[rnd.gen_range(0..ranges.len())].clone();
         if let Some(ch) = ::core::char::from_u32(
             rnd.gen_range(*range.start() as u32..*range.end() as u32 + 1),
         ) {
             return (*range.start() as u32, ch as u32 - *range.start() as u32);
         }
     }

     // Give up and return a character we at least know is valid.
     (*ranges[0].start() as u32, 0)
 }

 /// Strategy for generating `char`s.
 ///
 /// Character selection is more sophisticated than integer selection. Naïve
 /// selection (particularly in the larger context of generating strings) would
 /// result in starting inputs like `ꂡ螧轎ቶᢹ糦狥芹ᘆ㶏曊ᒀ踔虙ჲ` and "simplified"
 /// inputs consisting mostly of control characters. It also has difficulty
 /// locating edge cases, since the vast majority of code points (such as the
 /// enormous CJK regions) don't cause problems for anything with even basic
 /// Unicode support.
 ///
 /// Instead, character selection is always based on explicit ranges, and is
 /// designed to bias to specifically chosen characters and character ranges to
 /// produce inputs that are both more useful and easier for humans to
 /// understand. There are also hard-wired simplification targets based on ASCII
 /// instead of simply simplifying towards NUL to avoid problematic inputs being
 /// reduced to a bunch of NUL characters.
 ///
 /// Shrinking never crosses ranges. If you have a complex range like `[A-Za-z]`
 /// and the starting point `x` is chosen, it will not shrink to the first `A-Z`
 /// group, but rather simply to `a`.
 ///
 /// The usual way to get instances of this class is with the module-level `ANY`
 /// constant or `range` function. Directly constructing a `CharStrategy` is
 /// only necessary for complex ranges or to override the default biases.
 #[derive(Debug, Clone)]
 #[must_use = "strategies do nothing unless used"]
 pub struct CharStrategy<'a> {
     special: Cow<'a, [char]>,
     preferred: Cow<'a, [CharRange]>,
     ranges: Cow<'a, [CharRange]>,
 }

 impl<'a> CharStrategy<'a> {
     /// Construct a new `CharStrategy` with the parameters it will pass to the
     /// function underlying `select_char()`.
     ///
     /// All arguments as per `select_char()`.
     pub fn new(
         special: Cow<'a, [char]>,
         preferred: Cow<'a, [CharRange]>,
         ranges: Cow<'a, [CharRange]>,
     ) -> Self {
         CharStrategy {
             special,
             preferred,
             ranges,
         }
     }

     /// Same as `CharStrategy::new()` but using `Cow::Borrowed` for all parts.
     pub fn new_borrowed(
         special: &'a [char],
         preferred: &'a [CharRange],
         ranges: &'a [CharRange],
     ) -> Self {
         CharStrategy::new(
             Cow::Borrowed(special),
             Cow::Borrowed(preferred),
             Cow::Borrowed(ranges),
         )
     }
 }

 const WHOLE_RANGE: &[CharRange] = &['\x00'..=::core::char::MAX];

 /// Creates a `CharStrategy` which picks from literally any character, with the
 /// default biases.
 pub fn any() -> CharStrategy<'static> {
     CharStrategy {
         special: Cow::Borrowed(DEFAULT_SPECIAL_CHARS),
         preferred: Cow::Borrowed(DEFAULT_PREFERRED_RANGES),
         ranges: Cow::Borrowed(WHOLE_RANGE),
     }
 }

 /// Creates a `CharStrategy` which selects characters within the given
 /// endpoints, inclusive, using the default biases.
 pub fn range(start: char, end: char) -> CharStrategy<'static> {
     CharStrategy {
         special: Cow::Borrowed(DEFAULT_SPECIAL_CHARS),
         preferred: Cow::Borrowed(DEFAULT_PREFERRED_RANGES),
         ranges: Cow::Owned(vec![start..=end]),
     }
 }

 /// Creates a `CharStrategy` which selects characters within the given ranges,
 /// all inclusive, using the default biases.
 pub fn ranges(ranges: Cow<[CharRange]>) -> CharStrategy {
     CharStrategy {
         special: Cow::Borrowed(DEFAULT_SPECIAL_CHARS),
         preferred: Cow::Borrowed(DEFAULT_PREFERRED_RANGES),
         ranges,
     }
 }

 /// The `ValueTree` corresponding to `CharStrategy`.
 #[derive(Debug, Clone, Copy)]
 pub struct CharValueTree {
     value: num::u32::BinarySearch,
 }

 impl<'a> Strategy for CharStrategy<'a> {
     type Tree = CharValueTree;
     type Value = char;

     fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
         let (base, offset) = select_range_index(
             runner.rng(),
             &self.special,
             &self.preferred,
             &self.ranges,
         );

         // Select a minimum point more convenient than 0
         let start = base + offset;
         let bottom = if start >= '¡' as u32 && base < '¡' as u32 {
             '¡' as u32
         } else if start >= 'a' as u32 && base < 'a' as u32 {
             'a' as u32
         } else if start >= 'A' as u32 && base < 'A' as u32 {
             'A' as u32
         } else if start >= '0' as u32 && base < '0' as u32 {
             '0' as u32
         } else if start >= ' ' as u32 && base < ' ' as u32 {
             ' ' as u32
         } else {
             base
         };

         Ok(CharValueTree {
             value: num::u32::BinarySearch::new_above(bottom, start),
         })
     }
 }

 impl CharValueTree {
     fn reposition(&mut self) {
         while ::core::char::from_u32(self.value.current()).is_none() {
             if !self.value.complicate() {
                 panic!("Converged to non-char value");
             }
         }
     }
 }

 impl ValueTree for CharValueTree {
     type Value = char;

     fn current(&self) -> char {
         ::core::char::from_u32(self.value.current())
             .expect("Generated non-char value")
     }

     fn simplify(&mut self) -> bool {
         if self.value.simplify() {
             self.reposition();
             true
         } else {
             false
         }
     }

     fn complicate(&mut self) -> bool {
         if self.value.complicate() {
             self.reposition();
             true
         } else {
             false
         }
     }
 }

 #[cfg(test)]
 mod test {
     use std::cmp::{max, min};
     use std::vec::Vec;

     use super::*;
     use crate::collection;

     proptest! {
         #[test]
         fn stays_in_range(input_ranges in collection::vec(
             (0..::std::char::MAX as u32,
              0..::std::char::MAX as u32),
             1..5))
         {
             let input = ranges(Cow::Owned(input_ranges.iter().map(
                 |&(lo, hi)| ::std::char::from_u32(lo).and_then(
                     |lo| ::std::char::from_u32(hi).map(
                         |hi| min(lo, hi) ..= max(lo, hi)))
                     .ok_or_else(|| TestCaseError::reject("non-char")))
                                           .collect::<Result<Vec<CharRange>,_>>()?));

             let mut runner = TestRunner::default();
             for _ in 0..256 {
                 let mut value = input.new_tree(&mut runner).unwrap();
                 loop {
                     let ch = value.current() as u32;
                     assert!(input_ranges.iter().any(
                         |&(lo, hi)| ch >= min(lo, hi) &&
                             ch <= max(lo, hi)));

                     if !value.simplify() { break; }
                 }
             }
         }
     }

     #[test]
     fn applies_desired_bias() {
         let mut men_in_business_suits_levitating = 0;
         let mut ascii_printable = 0;
         let mut runner = TestRunner::deterministic();

         for _ in 0..1024 {
             let ch = any().new_tree(&mut runner).unwrap().current();
             if '🕴' == ch {
                 men_in_business_suits_levitating += 1;
             } else if ch >= ' ' && ch <= '~' {
                 ascii_printable += 1;
             }
         }

         assert!(ascii_printable >= 256);
         assert!(men_in_business_suits_levitating >= 1);
     }

     #[test]
     fn doesnt_shrink_to_ascii_control() {
         let mut accepted = 0;
         let mut runner = TestRunner::deterministic();

         for _ in 0..256 {
             let mut value = any().new_tree(&mut runner).unwrap();

             if value.current() <= ' ' {
                 continue;
             }

             while value.simplify() {}

             assert!(value.current() >= ' ');
             accepted += 1;
         }

         assert!(accepted >= 200);
     }

     #[test]
     fn test_sanity() {
         check_strategy_sanity(
             any(),
             Some(CheckStrategySanityOptions {
                 // `simplify()` can itself `complicate()` back to the starting
                 // position, so the overly strict complicate-after-simplify check
                 // must be disabled.
                 strict_complicate_after_simplify: false,
                 ..CheckStrategySanityOptions::default()
             }),
         );
     }
 }
	//-
	// 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.

	//! Strategies for generating `char` values.
	//!
	//! Unlike most strategies in Proptest, character generation is by default
	//! biased to particular values known to be difficult to handle in various
	//! circumstances.
	//!
	//! The main things of interest are `any()` to generate truly arbitrary
	//! characters, and `range()` and `ranges()` to select characters from
	//! inclusive ranges.

	use crate::std_facade::Cow;
	use core::ops::RangeInclusive;

	use rand::Rng;

	use crate::num;
	use crate::strategy::*;
	use crate::test_runner::*;

	/// An inclusive char range from fst to snd.
	type CharRange = RangeInclusive<char>;

	/// A default set of characters to consider as "special" during character
	/// generation.
	///
	/// Most of the characters here were chosen specifically because they are
	/// difficult to handle in particular contexts.
	pub const DEFAULT_SPECIAL_CHARS: &[char] = &[
	// Things to give shell scripts and filesystem logic difficulties
	'/', '\\', '$', '.', '*', '{', '\'', '"', '`', ':',
	// Characters with special significance in URLs and elsewhere
	'?', '%', '=', '&', '<',
	// Interesting ASCII control characters
	// NUL, HT, CR, LF, VT ESC DEL
	'\x00', '\t', '\r', '\n', '\x0B', '\x1B', '\x7F',
	// ¥ both to test simple Unicode handling and because it has interesting
	// properties on MS Shift-JIS systems.
	'¥', // No non-Unicode encoding has both ¥ and Ѩ
	'Ѩ',
	// In UTF-8, Ⱥ increases in length from 2 to 3 bytes when lowercased
	'Ⱥ',
	// More Unicode edge-cases: BOM, replacement character, RTL override, and non-BMP
	'\u{FEFF}', '\u{FFFD}', '\u{202E}', '🕴',
	];

	/// A default sequence of ranges used preferentially when generating random
	/// characters.
	pub const DEFAULT_PREFERRED_RANGES: &[CharRange] = &[
	// ASCII printable
	' '..='~',
	' '..='~',
	' '..='~',
	' '..='~',
	' '..='~',
	// Latin-1
	'\u{0040}'..='\u{00ff}',
	];

	/// Selects a random character the way `CharStrategy` does.
	///
	/// If `special` is non-empty, there is a 50% chance that a character from this
	/// array is chosen randomly, and will be returned if that character falls
	/// within `ranges`.
	///
	/// If `preferred` is non-empty, there is a 50% chance that any generation
	/// which gets past the `special` step picks a random element from this list,
	/// then a random character from within that range (both endpoints inclusive).
	/// That character will be returned if it falls within `ranges`.
	///
	/// In all other cases, an element is picked randomly from `ranges` and a
	/// random character within the range (both endpoints inclusive) is chosen and
	/// returned.
	///
	/// Notice that in all cases, `ranges` completely defines the set of characters
	/// that can possibly be defined.
	///
	/// It is legal for ranges in all cases to contain non-characters.
	///
	/// Both `preferred` and `ranges` bias selection towards characters in smaller
	/// ranges. This is deliberate. `preferred` is usually tuned to select
	/// particular characters anyway. `ranges` is usually derived from some
	/// external property, and the fact that a range is small often means it is
	/// more interesting.
	pub fn select_char(
	rnd: &mut impl Rng,
	special: &[char],
	preferred: &[CharRange],
	ranges: &[CharRange],
	) -> char {
	let (base, offset) = select_range_index(rnd, special, preferred, ranges);
	::core::char::from_u32(base + offset).expect("bad character selected")
	}

	fn select_range_index(
	rnd: &mut impl Rng,
	special: &[char],
	preferred: &[CharRange],
	ranges: &[CharRange],
	) -> (u32, u32) {
	fn in_range(ranges: &[CharRange], ch: char) -> Option<(u32, u32)> {
	ranges
	.iter()
	.find(\|r\| ch >= r.start() && ch <= r.end())
	.map(\|r\| (r.start() as u32, ch as u32 - r.start() as u32))
	}

	if !special.is_empty() && rnd.gen() {
	let s = special[rnd.gen_range(0..special.len())];
	if let Some(ret) = in_range(ranges, s) {
	return ret;
	}
	}

	if !preferred.is_empty() && rnd.gen() {
	let range = preferred[rnd.gen_range(0..preferred.len())].clone();
	if let Some(ch) = ::core::char::from_u32(
	rnd.gen_range(range.start() as u32..range.end() as u32 + 1),
	) {
	if let Some(ret) = in_range(ranges, ch) {
	return ret;
	}
	}
	}

	for _ in 0..65_536 {
	let range = ranges[rnd.gen_range(0..ranges.len())].clone();
	if let Some(ch) = ::core::char::from_u32(
	rnd.gen_range(range.start() as u32..range.end() as u32 + 1),
	) {
	return (range.start() as u32, ch as u32 - range.start() as u32);
	}
	}

	// Give up and return a character we at least know is valid.
	(*ranges[0].start() as u32, 0)
	}

	/// Strategy for generating `char`s.
	///
	/// Character selection is more sophisticated than integer selection. Naïve
	/// selection (particularly in the larger context of generating strings) would
	/// result in starting inputs like `ꂡ螧轎ቶᢹ糦狥芹ᘆ㶏曊ᒀ踔虙ჲ` and "simplified"
	/// inputs consisting mostly of control characters. It also has difficulty
	/// locating edge cases, since the vast majority of code points (such as the
	/// enormous CJK regions) don't cause problems for anything with even basic
	/// Unicode support.
	///
	/// Instead, character selection is always based on explicit ranges, and is
	/// designed to bias to specifically chosen characters and character ranges to
	/// produce inputs that are both more useful and easier for humans to
	/// understand. There are also hard-wired simplification targets based on ASCII
	/// instead of simply simplifying towards NUL to avoid problematic inputs being
	/// reduced to a bunch of NUL characters.
	///
	/// Shrinking never crosses ranges. If you have a complex range like `[A-Za-z]`
	/// and the starting point `x` is chosen, it will not shrink to the first `A-Z`
	/// group, but rather simply to `a`.
	///
	/// The usual way to get instances of this class is with the module-level `ANY`
	/// constant or `range` function. Directly constructing a `CharStrategy` is
	/// only necessary for complex ranges or to override the default biases.
	#[derive(Debug, Clone)]
	#[must_use = "strategies do nothing unless used"]
	pub struct CharStrategy<'a> {
	special: Cow<'a, [char]>,
	preferred: Cow<'a, [CharRange]>,
	ranges: Cow<'a, [CharRange]>,
	}

	impl<'a> CharStrategy<'a> {
	/// Construct a new `CharStrategy` with the parameters it will pass to the
	/// function underlying `select_char()`.
	///
	/// All arguments as per `select_char()`.
	pub fn new(
	special: Cow<'a, [char]>,
	preferred: Cow<'a, [CharRange]>,
	ranges: Cow<'a, [CharRange]>,
	) -> Self {
	CharStrategy {
	special,
	preferred,
	ranges,
	}
	}

	/// Same as `CharStrategy::new()` but using `Cow::Borrowed` for all parts.
	pub fn new_borrowed(
	special: &'a [char],
	preferred: &'a [CharRange],
	ranges: &'a [CharRange],
	) -> Self {
	CharStrategy::new(
	Cow::Borrowed(special),
	Cow::Borrowed(preferred),
	Cow::Borrowed(ranges),
	)
	}
	}

	const WHOLE_RANGE: &[CharRange] = &['\x00'..=::core::char::MAX];

	/// Creates a `CharStrategy` which picks from literally any character, with the
	/// default biases.
	pub fn any() -> CharStrategy<'static> {
	CharStrategy {
	special: Cow::Borrowed(DEFAULT_SPECIAL_CHARS),
	preferred: Cow::Borrowed(DEFAULT_PREFERRED_RANGES),
	ranges: Cow::Borrowed(WHOLE_RANGE),
	}
	}

	/// Creates a `CharStrategy` which selects characters within the given
	/// endpoints, inclusive, using the default biases.
	pub fn range(start: char, end: char) -> CharStrategy<'static> {
	CharStrategy {
	special: Cow::Borrowed(DEFAULT_SPECIAL_CHARS),
	preferred: Cow::Borrowed(DEFAULT_PREFERRED_RANGES),
	ranges: Cow::Owned(vec![start..=end]),
	}
	}

	/// Creates a `CharStrategy` which selects characters within the given ranges,
	/// all inclusive, using the default biases.
	pub fn ranges(ranges: Cow<[CharRange]>) -> CharStrategy {
	CharStrategy {
	special: Cow::Borrowed(DEFAULT_SPECIAL_CHARS),
	preferred: Cow::Borrowed(DEFAULT_PREFERRED_RANGES),
	ranges,
	}
	}

	/// The `ValueTree` corresponding to `CharStrategy`.
	#[derive(Debug, Clone, Copy)]
	pub struct CharValueTree {
	value: num::u32::BinarySearch,
	}

	impl<'a> Strategy for CharStrategy<'a> {
	type Tree = CharValueTree;
	type Value = char;

	fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
	let (base, offset) = select_range_index(
	runner.rng(),
	&self.special,
	&self.preferred,
	&self.ranges,
	);

	// Select a minimum point more convenient than 0
	let start = base + offset;
	let bottom = if start >= '¡' as u32 && base < '¡' as u32 {
	'¡' as u32
	} else if start >= 'a' as u32 && base < 'a' as u32 {
	'a' as u32
	} else if start >= 'A' as u32 && base < 'A' as u32 {
	'A' as u32
	} else if start >= '0' as u32 && base < '0' as u32 {
	'0' as u32
	} else if start >= ' ' as u32 && base < ' ' as u32 {
	' ' as u32
	} else {
	base
	};

	Ok(CharValueTree {
	value: num::u32::BinarySearch::new_above(bottom, start),
	})
	}
	}

	impl CharValueTree {
	fn reposition(&mut self) {
	while ::core::char::from_u32(self.value.current()).is_none() {
	if !self.value.complicate() {
	panic!("Converged to non-char value");
	}
	}
	}
	}

	impl ValueTree for CharValueTree {
	type Value = char;

	fn current(&self) -> char {
	::core::char::from_u32(self.value.current())
	.expect("Generated non-char value")
	}

	fn simplify(&mut self) -> bool {
	if self.value.simplify() {
	self.reposition();
	true
	} else {
	false
	}
	}

	fn complicate(&mut self) -> bool {
	if self.value.complicate() {
	self.reposition();
	true
	} else {
	false
	}
	}
	}

	#[cfg(test)]
	mod test {
	use std::cmp::{max, min};
	use std::vec::Vec;

	use super::*;
	use crate::collection;

	proptest! {
	#[test]
	fn stays_in_range(input_ranges in collection::vec(
	(0..::std::char::MAX as u32,
	0..::std::char::MAX as u32),
	1..5))
	{
	let input = ranges(Cow::Owned(input_ranges.iter().map(
	\|&(lo, hi)\| ::std::char::from_u32(lo).and_then(
	\|lo\| ::std::char::from_u32(hi).map(
	\|hi\| min(lo, hi) ..= max(lo, hi)))
	.ok_or_else(\|\| TestCaseError::reject("non-char")))
	.collect::<Result<Vec<CharRange>,_>>()?));

	let mut runner = TestRunner::default();
	for _ in 0..256 {
	let mut value = input.new_tree(&mut runner).unwrap();
	loop {
	let ch = value.current() as u32;
	assert!(input_ranges.iter().any(
	\|&(lo, hi)\| ch >= min(lo, hi) &&
	ch <= max(lo, hi)));

	if !value.simplify() { break; }
	}
	}
	}
	}

	#[test]
	fn applies_desired_bias() {
	let mut men_in_business_suits_levitating = 0;
	let mut ascii_printable = 0;
	let mut runner = TestRunner::deterministic();

	for _ in 0..1024 {
	let ch = any().new_tree(&mut runner).unwrap().current();
	if '🕴' == ch {
	men_in_business_suits_levitating += 1;
	} else if ch >= ' ' && ch <= '~' {
	ascii_printable += 1;
	}
	}

	assert!(ascii_printable >= 256);
	assert!(men_in_business_suits_levitating >= 1);
	}

	#[test]
	fn doesnt_shrink_to_ascii_control() {
	let mut accepted = 0;
	let mut runner = TestRunner::deterministic();

	for _ in 0..256 {
	let mut value = any().new_tree(&mut runner).unwrap();

	if value.current() <= ' ' {
	continue;
	}

	while value.simplify() {}

	assert!(value.current() >= ' ');
	accepted += 1;
	}

	assert!(accepted >= 200);
	}

	#[test]
	fn test_sanity() {
	check_strategy_sanity(
	any(),
	Some(CheckStrategySanityOptions {
	// `simplify()` can itself `complicate()` back to the starting
	// position, so the overly strict complicate-after-simplify check
	// must be disabled.
	strict_complicate_after_simplify: false,
	..CheckStrategySanityOptions::default()
	}),
	);
	}
	}