Probar

Playwright-Compatible Testing for WASM + TUI Applications
Pure Rust • Zero JavaScript • Games • Simulations • Web Apps

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Installation

Probar (Spanish: "to test/prove") is distributed as two crates:

Crate	Purpose	Install
jugar-probar	Library for writing tests	cargo add jugar-probar --dev
probador	CLI tool for running tests	cargo install probador

Library (jugar-probar)

Add to your Cargo.toml:

[dev-dependencies]
jugar-probar = "0.3"

use jugar_probar::prelude::*;

CLI (probador)

cargo install probador

# Validate a playbook state machine
probador playbook login.yaml --validate

# Run with mutation testing (M1-M5 falsification)
probador playbook login.yaml --mutate

# Export state diagram
probador playbook login.yaml --export svg -o diagram.svg

# Start dev server for WASM
probador serve --port 8080

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Overview

Probar is a Playwright-compatible testing framework written in pure Rust. It provides comprehensive testing for:

• WASM Applications - Games, simulations, web apps running in browsers
• TUI Applications - Terminal interfaces built with ratatui/crossterm
• Headless Testing - Fast CI/CD without browser overhead

Key Features

GUI Coverage Tracking

Probar introduces GUI Coverage - a new paradigm for measuring UI test completeness:

use jugar_probar::gui_coverage;

// Define what needs testing (one line!)
let mut gui = gui_coverage! {
    buttons: ["start", "pause", "quit"],
    screens: ["title", "playing", "game_over"]
};

// Record interactions during tests
gui.click("start");
gui.visit("title");

// Get coverage - one line!
println!("{}", gui.summary());  // "GUI: 33% (1/3 elements, 1/3 screens)"
assert!(gui.meets(80.0));       // Fail if below 80%

Playwright-Compatible API

// Familiar Playwright-style locators and assertions
let button = page.locator("button").with_text("Start Game");
button.click().await?;

expect(&score).to_have_text("100").await?;

Test Targets

Target	Description	Use Case
WASM Browser	Chrome DevTools Protocol (CDP)	Games, web apps, simulations
WASM Headless	wasmtime runtime	Fast CI, logic testing
TUI	ratatui/crossterm backends	Terminal applications

Core Capabilities

Feature	Description
Browser Automation	Chrome DevTools Protocol (CDP) via chromiumoxide
WASM Runtime Testing	Logic-only testing via wasmtime (no browser overhead)
TUI Testing	Frame capture and assertion for terminal UIs
GUI Coverage	Provable UI element and interaction coverage
Visual Regression	Image comparison for UI stability
Accessibility Auditing	WCAG compliance checking
Deterministic Replay	Record and replay sessions with seed control
Monte Carlo Fuzzing	Random input generation with invariant checking

Quick Start

use jugar_probar::prelude::*;

#[test]
fn test_calculator_gui() {
    // Create driver (works for TUI or WASM)
    let mut driver = WasmDriver::new();

    // Track GUI coverage
    let mut gui = gui_coverage! {
        buttons: ["btn-7", "btn-times", "btn-6", "btn-equals"],
        screens: ["calculator"]
    };

    // Test: 7 x 6 = 42
    driver.type_input("7 * 6");
    gui.click("btn-7");
    gui.click("btn-times");
    gui.click("btn-6");

    driver.click_equals();
    gui.click("btn-equals");
    gui.visit("calculator");

    assert_eq!(driver.get_result(), "42");
    assert!(gui.is_complete());  // 100% GUI coverage!
}

Feature Flags

Feature	Description	Dependencies
tui	TUI testing support (default)	ratatui, crossterm
browser	CDP browser automation	chromiumoxide, tokio
runtime	WASM runtime testing	wasmtime
derive	Type-safe derive macros	probar-derive

Usage

Running Tests

# Run all tests
cargo test

# Run with coverage
cargo llvm-cov --html

# Watch mode
cargo watch -x test

Using probador CLI

# Run tests with probador
probador test

# Generate coverage reports
probador coverage --html

# Watch mode with hot reload
probador watch tests/

# Serve WASM application
probador serve --port 8080 --cors

GUI Coverage Example

# Run the GUI coverage example
cargo run --example gui_coverage -p jugar-probar

Output:

=== GUI Coverage Example ===

1. Using gui_coverage! macro (simplest)...
   GUI: 50% (1/3 elements, 2/3 screens)

2. Calculator preset (20 buttons + 2 screens)...
   GUI: 60% (14/20 elements, 1/2 screens)

3. Achieving 100% coverage...
   GUI: 100% (3/3 elements, 1/1 screens)
   Complete? true

Showcase Calculator

The repository includes a full showcase calculator demonstrating 100% test coverage:

# Run GUI coverage report
cargo run -p showcase-calculator --example gui_coverage_report

# Run TUI version
cargo run -p showcase-calculator --example calculator_tui

# View WASM version
cd crates/showcase-calculator/www && python3 -m http.server 8080
# Open http://localhost:8080

Probar Principles

Probar is built on pragmatic testing principles:

Principle	Description
Error Prevention	Type-safe selectors prevent runtime errors
Efficiency	Zero-copy memory views minimize overhead
Fail-Fast	Immediate feedback on test failures
Balanced Testing	Even coverage across all UI elements
Continuous Improvement	Mutation testing for test quality

Documentation

• Book - Comprehensive guide
• API Docs - Rust documentation
• GUI Coverage Guide - GUI coverage tutorial
• Examples - 20+ runnable examples

Examples

Example	Description
gui_coverage	GUI coverage tracking
soft_assertions	Collect multiple failures
retry_assertions	Retry with backoff
pong_simulation	Game simulation testing
accessibility_demo	WCAG compliance
watch_mode	Hot-reload testing

Run any example:

cargo run --example <name> -p jugar-probar

Project Structure

probar/
├── crates/
│   ├── probar/              # jugar-probar library
│   ├── probar-cli/          # probador CLI
│   ├── probar-derive/       # Derive macros
│   └── showcase-calculator/ # 100% coverage demo
├── book/                    # mdBook documentation
└── docs/                    # Specifications

Contributing

Contributions are welcome! Please follow these guidelines:

1. Fork the repository and create your branch from main
2. Run tests before submitting: cargo test
3. Ensure formatting: cargo fmt
4. Check lints: cargo clippy --all-targets --all-features
5. Update documentation if you change public APIs
6. Add tests for new functionality

Development Setup

git clone https://github.com/paiml/probar.git
cd probar
cargo build
cargo test

Quality Gates

make lint      # Clippy checks
make test      # All tests
make coverage  # Coverage report

License

MIT OR Apache-2.0

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Probar - by Pragmatic AI Labs