Struct PropertySnapshots 

pub struct PropertySnapshots { /* private fields */ }

Helper for managing property-based snapshots

This struct provides convenient methods for creating multiple snapshots in property-based tests. Each snapshot gets an automatic sequential name.

Example

use protest::{Generator, primitives::IntGenerator, config::GeneratorConfig};
use protest_insta::PropertySnapshots;
use rand::SeedableRng;
use rand::rngs::StdRng;

#[test]
fn test_with_property_snapshots() {
    let mut rng = StdRng::seed_from_u64(42);
    let config = GeneratorConfig::default();
    let generator = IntGenerator::new(0, 100);

    let mut snapshots = PropertySnapshots::new("test_case");

    for _ in 0..5 {
        let value = generator.generate(&mut rng, &config);
        snapshots.assert_debug_snapshot(&value);
    }
}

Implementations

impl PropertySnapshots

pub fn new(base_name: impl Into<String>) -> Self

Create a new PropertySnapshots helper with the given base name

Arguments

• base_name - The base name for all snapshots in this group

Example

use protest_insta::PropertySnapshots;

let mut snapshots = PropertySnapshots::new("my_test");
// Will create snapshots named: my_test_0, my_test_1, my_test_2, ...

Examples found in repository

examples/debug_snapshots.rs (line 57)

fn main() {
    println!("=== Debug Snapshot Testing Example ===\n");

    // Create a seeded RNG for reproducibility
    let mut rng = StdRng::seed_from_u64(123);
    let config = GeneratorConfig::default();

    // Create generator for small integers
    let generator = IntGenerator::new(1, 15);

    // Create snapshot helper
    let mut snapshots = PropertySnapshots::new("computations");

    println!("Computing results for 8 generated inputs...\n");

    // Generate and snapshot 8 computation results
    for i in 0..8 {
        let input = generator.generate(&mut rng, &config);
        let result = compute(input);

        println!("Computation {}: {:?}", i, result);

        // Create a debug snapshot
        snapshots.assert_debug_snapshot(&result);
    }

    println!("\n✅ Created 8 debug snapshots in snapshots/ directory");
    println!("   Review them with: cargo insta review");
}

examples/json_snapshots.rs (line 41)

fn main() {
    println!("=== JSON Snapshot Testing Example ===\n");

    // Create a seeded RNG for reproducibility
    let mut rng = StdRng::seed_from_u64(42);
    let config = GeneratorConfig::default();

    // Create generators
    let id_generator = IntGenerator::new(1, 1000);
    let score_generator = VecGenerator::new(IntGenerator::new(0, 100), 1, 10);

    // Create snapshot helper
    let mut snapshots = PropertySnapshots::new("user_profiles");

    println!("Generating 5 user profiles and creating JSON snapshots...\n");

    // Generate and snapshot 5 different user profiles
    for i in 0..5 {
        let user_id = id_generator.generate(&mut rng, &config);
        let username = generate_username(user_id);
        let scores = score_generator.generate(&mut rng, &config);
        let total_score: i32 = scores.iter().sum();
        let is_premium = total_score > 250;

        let profile = UserProfile {
            user_id,
            username,
            scores: scores.clone(),
            total_score,
            is_premium,
        };

        println!("Profile {}: {:?}", i, profile);

        // Create a JSON snapshot - this will create files in snapshots/
        snapshots.assert_json_snapshot(&profile);
    }

    println!("\n✅ Created 5 JSON snapshots in snapshots/ directory");
    println!("   Review them with: cargo insta review");
}

pub fn assert_json_snapshot<T: Serialize>(&mut self, value: &T)

Assert a JSON snapshot for the given value

This serializes the value to pretty-printed JSON and creates a snapshot.

Arguments

• value - The value to snapshot (must implement Serialize)

Example

use protest_insta::PropertySnapshots;
use serde::Serialize;

#[derive(Serialize)]
struct Config { port: u16, host: String }

let mut snapshots = PropertySnapshots::new("config");
let cfg = Config { port: 8080, host: "localhost".to_string() };
snapshots.assert_json_snapshot(&cfg);

Examples found in repository

examples/property_snapshot_test.rs (line 44)

fn main() {
    println!("=== Property Snapshot Test Function Example ===\n");
    println!("Testing mathematical operations with property-based inputs...\n");

    // Use the helper function for concise testing
    property_snapshot_test(
        "math_operations",
        IntGenerator::new(-10, 10),
        10,  // Generate 10 test cases
        456, // Seed for reproducibility
        |value, snapshots| {
            let result = perform_operations(value);
            println!("Operation on {}: {:?}", value, result);
            snapshots.assert_json_snapshot(&result);
        },
    );

    println!("\n✅ Created 10 snapshots in snapshots/ directory");
    println!("   Review them with: cargo insta review");
    println!("\nNote: This example uses the property_snapshot_test helper");
    println!("      which combines generator setup with snapshot management.");
}

examples/json_snapshots.rs (line 64)

fn main() {
    println!("=== JSON Snapshot Testing Example ===\n");

    // Create a seeded RNG for reproducibility
    let mut rng = StdRng::seed_from_u64(42);
    let config = GeneratorConfig::default();

    // Create generators
    let id_generator = IntGenerator::new(1, 1000);
    let score_generator = VecGenerator::new(IntGenerator::new(0, 100), 1, 10);

    // Create snapshot helper
    let mut snapshots = PropertySnapshots::new("user_profiles");

    println!("Generating 5 user profiles and creating JSON snapshots...\n");

    // Generate and snapshot 5 different user profiles
    for i in 0..5 {
        let user_id = id_generator.generate(&mut rng, &config);
        let username = generate_username(user_id);
        let scores = score_generator.generate(&mut rng, &config);
        let total_score: i32 = scores.iter().sum();
        let is_premium = total_score > 250;

        let profile = UserProfile {
            user_id,
            username,
            scores: scores.clone(),
            total_score,
            is_premium,
        };

        println!("Profile {}: {:?}", i, profile);

        // Create a JSON snapshot - this will create files in snapshots/
        snapshots.assert_json_snapshot(&profile);
    }

    println!("\n✅ Created 5 JSON snapshots in snapshots/ directory");
    println!("   Review them with: cargo insta review");
}

pub fn assert_debug_snapshot<T: Debug>(&mut self, value: &T)

Assert a debug snapshot for the given value

This uses the Debug trait to format the value and creates a snapshot.

Arguments

• value - The value to snapshot (must implement Debug)

Example

use protest_insta::PropertySnapshots;

let mut snapshots = PropertySnapshots::new("numbers");
let values = vec![1, 2, 3, 4, 5];
snapshots.assert_debug_snapshot(&values);

Examples found in repository

examples/debug_snapshots.rs (line 69)

fn main() {
    println!("=== Debug Snapshot Testing Example ===\n");

    // Create a seeded RNG for reproducibility
    let mut rng = StdRng::seed_from_u64(123);
    let config = GeneratorConfig::default();

    // Create generator for small integers
    let generator = IntGenerator::new(1, 15);

    // Create snapshot helper
    let mut snapshots = PropertySnapshots::new("computations");

    println!("Computing results for 8 generated inputs...\n");

    // Generate and snapshot 8 computation results
    for i in 0..8 {
        let input = generator.generate(&mut rng, &config);
        let result = compute(input);

        println!("Computation {}: {:?}", i, result);

        // Create a debug snapshot
        snapshots.assert_debug_snapshot(&result);
    }

    println!("\n✅ Created 8 debug snapshots in snapshots/ directory");
    println!("   Review them with: cargo insta review");
}

pub fn assert_yaml_snapshot<T: Serialize>(&mut self, value: &T)

Assert a YAML snapshot for the given value

This serializes the value to YAML and creates a snapshot.

Arguments

• value - The value to snapshot (must implement Serialize)

Example

use protest_insta::PropertySnapshots;
use serde::Serialize;

#[derive(Serialize)]
struct Settings { debug: bool, timeout: u64 }

let mut snapshots = PropertySnapshots::new("settings");
let s = Settings { debug: true, timeout: 30 };
snapshots.assert_yaml_snapshot(&s);

pub fn reset(&mut self)

Reset the counter back to 0

Useful if you want to reuse the same PropertySnapshots instance with a different set of tests.

Example

use protest_insta::PropertySnapshots;

let mut snapshots = PropertySnapshots::new("test");
// ... use snapshots ...
snapshots.reset();
// Counter is back to 0

pub fn count(&self) -> usize

Get the current counter value

Example

use protest_insta::PropertySnapshots;

let mut snapshots = PropertySnapshots::new("test");
assert_eq!(snapshots.count(), 0);