checkito 5.0.0

A safe, efficient and simple QuickCheck-inspired library to generate shrinkable random data mainly oriented towards generative/property/exploratory testing.
Documentation 
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pub mod common;
use checkito::Generate;
use common::*;

#[test]
fn u8_full_range_has_correct_cardinality() {
    let generator = u8::generator();
    assert_eq!(generator.cardinality(), Some(256));
}

#[test]
fn i8_full_range_has_correct_cardinality() {
    let generator = i8::generator();
    assert_eq!(generator.cardinality(), Some(256));
}

#[test]
fn u16_full_range_has_correct_cardinality() {
    let generator = u16::generator();
    assert_eq!(generator.cardinality(), Some(65536));
}

#[test]
fn i16_full_range_has_correct_cardinality() {
    let generator = i16::generator();
    assert_eq!(generator.cardinality(), Some(65536));
}

#[test]
fn u32_full_range_has_correct_cardinality() {
    let generator = u32::generator();
    assert_eq!(generator.cardinality(), Some(4294967296));
}

#[test]
fn i32_full_range_has_correct_cardinality() {
    let generator = i32::generator();
    assert_eq!(generator.cardinality(), Some(4294967296));
}

#[test]
fn u64_full_range_has_correct_cardinality() {
    let generator = u64::generator();
    assert_eq!(generator.cardinality(), Some(18446744073709551616));
}

#[test]
fn i64_full_range_has_correct_cardinality() {
    let generator = i64::generator();
    assert_eq!(generator.cardinality(), Some(18446744073709551616));
}

#[test]
fn u128_full_range_has_correct_cardinality() {
    let generator = u128::generator();
    // u128 has 2^128 values, which overflows u128; cardinality should be None
    assert_eq!(generator.cardinality(), None);
}

#[test]
fn i128_full_range_has_correct_cardinality() {
    let generator = i128::generator();
    // i128 has 2^128 values, which overflows u128; cardinality should be None
    assert_eq!(generator.cardinality(), None);
}

#[test]
fn char_full_range_has_correct_cardinality() {
    let generator = char::generator();
    // char excludes surrogate code points U+D800..=U+DFFF (2,048 values)
    // 1,114,112 total - 2,048 surrogates = 1,112,064
    assert_eq!(generator.cardinality(), Some(1_112_064));
}

#[test]
fn char_surrogate_spanning_range_has_correct_cardinality() {
    // Range spanning the surrogate gap: U+D7FF and U+E000 are valid, surrogates are
    // not
    let generator = '\u{D7FF}'..='\u{E000}';
    // 0xE000 - 0xD7FF + 1 = 2050 total code points, minus 2048 surrogates = 2
    assert_eq!(generator.cardinality(), Some(2));
}

#[test]
fn custom_u8_range_has_correct_cardinality() {
    let generator = 10u8..=20;
    // Range from 10 to 20 inclusive = 11 values
    assert_eq!(generator.cardinality(), Some(11));
}

#[test]
fn custom_i8_range_has_correct_cardinality() {
    let generator = -5i8..=5;
    // Range from -5 to 5 inclusive = 11 values
    assert_eq!(generator.cardinality(), Some(11));
}

#[test]
fn custom_char_range_has_correct_cardinality() {
    let generator = 'a'..='z';
    // Range from 'a' to 'z' inclusive = 26 values
    assert_eq!(generator.cardinality(), Some(26));
}

#[test]
fn single_value_range_has_cardinality_one() {
    let generator = 42u8..=42;
    assert_eq!(generator.cardinality(), Some(1));
}

#[test]
fn f32_full_range_has_correct_cardinality() {
    let generator = f32::generator();
    // All non-NaN values (finite + both infinities) + 1 for NaN (all NaN patterns
    // treated as one).
    assert_eq!(generator.cardinality(), Some(4278190083));
}

#[test]
fn f64_full_range_has_correct_cardinality() {
    let generator = f64::generator();
    // All non-NaN values (finite + both infinities) + 1 for NaN (all NaN patterns
    // treated as one).
    assert_eq!(generator.cardinality(), Some(18437736874454810627));
}

#[test]
fn f32_full_cardinality_equals_finite_plus_infinities_plus_nan() {
    // The full f32 cardinality is: all finite values (MIN..=MAX) + NEG_INFINITY +
    // INFINITY + NaN. The generator covers all three: finite via range
    // branches, ±INF and NaN via the Special branch.
    let finite = (f32::MIN..=f32::MAX).cardinality().unwrap();
    assert_eq!(f32::generator().cardinality(), Some(finite + 3));
}

#[test]
fn f64_full_cardinality_equals_finite_plus_infinities_plus_nan() {
    // The full f64 cardinality is: all finite values (MIN..=MAX) + NEG_INFINITY +
    // INFINITY + NaN. The generator covers all three: finite via range
    // branches, ±INF and NaN via the Special branch.
    let finite = (f64::MIN..=f64::MAX).cardinality().unwrap();
    assert_eq!(f64::generator().cardinality(), Some(finite + 3));
}

#[test]
fn full_usize_has_correct_cardinality() {
    let generator = usize::generator();
    let range = (usize::MAX as u128) - (usize::MIN as u128);
    let expected = range.checked_add(1);
    match expected {
        Some(value) => assert_eq!(generator.cardinality(), Some(value)),
        None => assert_eq!(generator.cardinality(), None),
    }
}

#[test]
fn full_isize_has_correct_cardinality() {
    let generator = isize::generator();
    let range = u128::wrapping_sub(isize::MAX as u128, isize::MIN as u128);
    let expected = range.checked_add(1);
    match expected {
        Some(value) => assert_eq!(generator.cardinality(), Some(value)),
        None => assert_eq!(generator.cardinality(), None),
    }
}

// Inverse ranges (end < start) are normalized to their forward counterpart,
// so cardinality matches sampling: both see the same [low, high] range.
#[test]
#[allow(clippy::reversed_empty_ranges)]
fn inverse_u8_range_has_same_cardinality_as_forward() {
    // 10u8..=0 is normalized to Range(0, 10) — identical to 0u8..=10
    #[allow(clippy::reversed_empty_ranges)]
    let inv: std::ops::RangeInclusive<u8> = 10u8..=0;
    assert_eq!(inv.cardinality(), Some(11));
    assert_eq!((0u8..=10).cardinality(), Some(11));
}

#[test]
#[allow(clippy::reversed_empty_ranges)]
fn inverse_i32_range_has_same_cardinality_as_forward() {
    #[allow(clippy::reversed_empty_ranges)]
    let inv: std::ops::RangeInclusive<i32> = 100i32..=-100;
    assert_eq!(inv.cardinality(), Some(201));
    assert_eq!((-100i32..=100).cardinality(), Some(201));
}

#[test]
#[allow(clippy::reversed_empty_ranges)]
fn inverse_char_range_has_same_cardinality_as_forward() {
    // 'z'..='a' is normalized to Range('a', 'z') — 26 values
    assert_eq!(('z'..='a').cardinality(), Some(26));
    assert_eq!(('a'..='z').cardinality(), Some(26));
}

#[test]
#[allow(clippy::reversed_empty_ranges)]
fn inverse_u8_full_range_has_same_cardinality_as_forward() {
    // u8::MAX..=u8::MIN normalizes to Range(0, 255) — all 256 values
    #[allow(clippy::reversed_empty_ranges)]
    let inv: std::ops::RangeInclusive<u8> = u8::MAX..=u8::MIN;
    assert_eq!(inv.cardinality(), Some(256));
    assert_eq!((u8::MIN..=u8::MAX).cardinality(), Some(256),);
}

#[test]
fn lazy_delegates_cardinality_to_inner_range() {
    let generator = lazy(|| 0u8..=10);
    assert_eq!(generator.cardinality(), Some(256));
    generator.sample(1.0);
    assert_eq!(generator.cardinality(), Some(11));
}

#[test]
fn lazy_delegates_cardinality_to_inner_bool() {
    let generator = lazy(bool::generator);
    assert_eq!(generator.cardinality(), Some(2));
    generator.sample(1.0);
    assert_eq!(generator.cardinality(), Some(2));
}

#[test]
fn lazy_delegates_cardinality_to_inner_unbounded() {
    let generator = lazy(u128::generator);
    assert_eq!(generator.cardinality(), None);
    generator.sample(1.0);
    assert_eq!(generator.cardinality(), None);
}

#[cfg(feature = "check")]
mod check {
    use super::*;

    #[check(_, _)]
    fn u8_range_cardinality_matches_width(start: u8, end: u8) {
        let (low, high) = if start <= end {
            (start, end)
        } else {
            (end, start)
        };
        assert_eq!(
            (low..=high).cardinality(),
            Some(u128::from(high - low) + 1)
        );
    }

    #[check(_, _)]
    fn i16_range_cardinality_matches_width(start: i16, end: i16) {
        let (low, high) = if start <= end {
            (start, end)
        } else {
            (end, start)
        };
        // Use i128 subtraction which cannot overflow for i16 operands.
        let expected = (high as i128 - low as i128 + 1) as u128;
        assert_eq!((low..=high).cardinality(), Some(expected));
    }

    #[check(_)]
    fn single_value_range_has_cardinality_one(value: u8) {
        assert_eq!((value..=value).cardinality(), Some(1));
    }

    #[check(_, _)]
    fn char_range_cardinality_is_consistent(start: char, end: char) {
        let (low, high) = if start <= end {
            (start, end)
        } else {
            (end, start)
        };
        let cardinality = (low..=high).cardinality();
        // Cardinality should always be at least 1 for a valid range.
        assert!(cardinality.unwrap() >= 1);
    }
}