Regrest

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Regrest is a simple and powerful regression testing tool for Python. It automatically records function outputs on the first run and validates them on subsequent runs.

Features

• 🎯 Simple decorator-based API - Just add @regrest to your functions
• 📝 Automatic recording - First run records outputs, subsequent runs validate
• 🔍 Smart comparison - Handles floats, dicts, lists, nested structures, and custom classes
• 🛠 CLI tools - List, view, delete, and visualize test records
• 📊 Web visualization - Beautiful dashboard with JSONesque display, hierarchical navigation, and hot reload
• ⚙️ Configurable - Custom tolerance, storage location, and more
• 🔧 Auto .gitignore - Automatically creates .regrest/.gitignore to exclude test records on first run

Requirements

• Python 3.9 or higher

Installation

pip install regrest

# Optional: Install with Flask for better server performance
pip install regrest[server]

Quick Start

Basic Usage

from regrest import regrest

@regrest
def calculate_price(items, discount=0):
    total = sum(item['price'] for item in items)
    return total * (1 - discount)

# First run: records the result
items = [{'price': 100}, {'price': 200}]
result = calculate_price(items, discount=0.1)  # Returns 270.0, records it
# Output: [regrest] Recorded: __main__.calculate_price (id: abc123...)

# Second run: validates against recorded result
result = calculate_price(items, discount=0.1)  # Returns 270.0, compares with record
# Output: [regrest] Passed: __main__.calculate_price (id: abc123...)

Custom Tolerance

@regrest(tolerance=1e-6)
def calculate_pi():
    return 3.14159265359

Update Mode

To update existing records instead of testing:

@regrest(update=True)
def my_function():
    return "new result"

Or set the environment variable:

REGREST_UPDATE_MODE=1 python your_script.py

Environment Variables

Priority: Constructor arguments > Environment variables > Default values

CLI Commands

List Records

regrest list              # List all records
regrest list -k calculate # Filter by keyword

Lists all test records with module, function, arguments, results, and timestamps.

Delete Records

regrest delete abc123def456      # Delete by ID
regrest delete --pattern "test_*" # Delete by pattern
regrest delete --all             # Delete all records

Serve Web UI

regrest serve                    # Start on localhost:8000
regrest serve --port 8080        # Custom port
regrest serve --host 0.0.0.0     # Allow external access
regrest serve --reload           # Enable hot reload

Access the web UI at http://localhost:8000 for:

• Hierarchical view - Organized by module → function → record
• Search & filter - Find records by keyword
• JSONesque display - Syntax-highlighted, readable format
• Record management - Delete individual or all records

Architecture

System Overview

graph TB
    subgraph "User Code"
        A[Decorated Function<br/>@regrest]
    end

    subgraph "Regrest Core"
        B[Decorator<br/>decorator.py]
        C[Storage<br/>storage.py]
        D[Matcher<br/>matcher.py]
        E[Config<br/>config.py]
        F[Exceptions<br/>exceptions.py]
    end

    subgraph "Storage Layer"
        G[JSON Files<br/>.regrest/*.json]
        H[Pickle Serialization<br/>base64 encoded]
    end

    subgraph "CLI & Server"
        I[CLI<br/>typer-based]
        J[Web Server<br/>Flask/HTTP]
        K[Web UI<br/>Tailwind CSS]
    end

    A --> B
    B --> C
    B --> D
    B --> E
    B --> F
    C --> G
    C --> H
    I --> C
    J --> C
    J --> K

    style A fill:#e1f5ff
    style B fill:#fff4e1
    style C fill:#f0e1ff
    style D fill:#e1ffe1
    style I fill:#ffe1e1
    style J fill:#ffe1e1

How It Works

1. First Run: When you call a function decorated with @regrest, it executes normally and saves:

   • Module and function name
   • Arguments (args and kwargs)
   • Return value
   • Timestamp

   The record is saved to .regrest/ directory as a JSON file.

2. Subsequent Runs: On the next call with the same arguments:

   • The function executes
   • The result is compared with the recorded value
   • If they match → Test passes ✅
   • If they don't match → RegressionTestError is raised ❌

3. Update Mode: When you need to update the expected values:

   • Use @regrest(update=True) or REGREST_UPDATE_MODE=1
   • The old record is replaced with the new result

Configuration

Advanced Features

Comparison Logic

The matcher intelligently compares:

• Primitives: Exact match for strings, booleans
• Numbers: Tolerance-based for floats, exact for integers
• Collections: Deep comparison for lists, dicts, sets
• Nested structures: Recursive comparison with detailed error messages

Storage Format

File Structure

Records are stored as JSON files in the .regrest/ directory:

.regrest/
├── .gitignore                                    # Auto-generated
├── example.calculate_price.a1b2c3d4.json       # Record file
└── mymodule.process_data.e5f6g7h8.json        # Record file

File Naming Convention

{module}.{function}.{record_id}.json

Record ID Generation: Records are uniquely identified by:

1. Module name
2. Function name
3. SHA256 hash of serialized arguments (args + kwargs)

This means different argument combinations create separate records for the same function.

Encoding Strategy

Regrest uses a hybrid encoding approach for maximum compatibility and readability:

Advantages:

• ✅ Readable: Simple data types are stored as JSON for easy inspection
• ✅ Flexible: Complex objects are automatically pickled
• ✅ Version control friendly: JSON format produces clean diffs

Considerations:

• ⚠️ Pickle compatibility: May have issues across different Python versions
• ⚠️ Custom classes: Must be pickle-serializable and implement __eq__ for comparison

Best Practices

Limitations

Contributing

Contributions welcome! Run make check before submitting PRs.

License

MIT License

Changelog

0.1.0 (Initial Release)

• Published to PyPI - Install with pip install regrest
• Core decorator functionality (@regrest)
• Hybrid JSON/Pickle storage system
• Smart comparison with floating-point tolerance
• CLI tools (regrest list, regrest delete)
• Custom class support
• Auto .gitignore generation
• Environment variable configuration
• Colorful logging output
• Python 3.9+ support
• pyproject.toml-based build system
• ruff + mypy static analysis
• Makefile task automation
• GitHub Actions CI/CD