Module shrinking 

Enhanced shrinking strategies for Protest

This module provides advanced shrinking strategies that go beyond basic shrinking:

• Smart Shrinking: Preserve invariants while shrinking
• Delta Debugging: Binary search for minimal failing subsets
• Targeted Shrinking: Shrink toward specific target values

Examples

Smart Shrinking with Invariants

use protest_extras::shrinking::SmartShrink;

let mut sorted_vec = vec![1, 3, 5, 7, 9];

// Shrink while keeping the vector sorted
let shrunk = sorted_vec.shrink_preserving(|v| {
    v.windows(2).all(|w| w[0] <= w[1])
});

for candidate in shrunk {
    // All candidates remain sorted
    assert!(candidate.windows(2).all(|w| w[0] <= w[1]));
}

Delta Debugging

use protest_extras::shrinking::DeltaDebugShrinker;

let operations = vec![1, 2, 3, 4, 5, 6, 7, 8];

// Find minimal subset that fails a test
let shrinker = DeltaDebugShrinker::new(operations);
let minimal = shrinker.find_minimal(|ops| {
    // Only fails if contains both 3 and 7
    ops.contains(&3) && ops.contains(&7)
});

assert_eq!(minimal, vec![3, 7]); // Minimal failing case

Structs

CascadingShrinker

Cascading shrinker that applies multiple shrinking strategies in sequence

ConfigurableShrinker

Configurable shrinker with search strategy control

DeltaDebugIterator

Iterator that yields shrinking steps

DeltaDebugShrinker

Delta debugging shrinker for finding minimal failing subsets

GuidedShrinker

Guided shrinker that uses test feedback to prioritize shrinking directions

TargetedShrinkIterator

Iterator for targeted shrinking

TargetedShrinker

Shrinker that shrinks toward a specific target value

Enums

ShrinkStrategy

Search strategy for shrinking

Traits

SmartShrink

Trait for shrinking values while preserving invariants