Sprintest

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Sprintest is a high-performance Client-Server (C/S) architecture test runner specifically engineered for heavy AI/ML projects.

In projects involving large language models (LLMs), deep learning frameworks (PyTorch, TensorFlow), or massive datasets, standard test runners suffer from excruciatingly slow startup times (often 30s to several minutes) because they re-initialize the entire environment for every run. Sprintest solves this by keeping your heavy dependencies pre-loaded in memory.

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🚀 Key Highlights

• ⚡ Blazing Fast Feedback: Reduces test startup time from minutes to milliseconds by keeping heavy frameworks and models pre-loaded in a background daemon.
• 🔄 Intelligent Hot-Reloading: Features a "Nuke Engine" that surgically unloads only your project's modified modules, ensuring you always test against the latest code without losing the pre-loaded state.
• 🔌 Unified Transport Layer: Automatically chooses between Unix Domain Sockets (UDS) for zero-latency local communication and TCP for maximum compatibility.
• 🛠️ Decoupled Architecture: Built with a robust service layer and atomic state management, ensuring stable communication even during heavy test execution.
• 🤖 Agent-Optimized: Designed for AI coding agents (like Antigravity or Cursor) with clean, ANSI-free output and reliable status tracking.
• 🎯 Configurable Strategy: Fine-tune hot-reloading with ignore_patterns in your pyproject.toml to prevent specific heavy modules from being reloaded.

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⚡ Performance Comparison

For AI/ML projects with heavy dependencies (torch, transformers, etc.), Sprintest provides a massive speedup by eliminating redundant initialization.

Run Type	Total Time
Pytest (Standard)	~6.0s
Sprintest (First Run)	~7.0s
Sprintest (Warm Start)	~2.0s

Numbers above are measured on examples/test_ai_model.py and are provided for reference only. In heavier real-world projects, speedups typically reach 5x - 10x—for example, in my other project engram-peft, unit test total wall time improved by 7.8x (integration tests not included).

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🏗️ Architecture

Sprintest uses a decoupled architecture to ensure the daemon remains responsive even when running heavy tests.

New Highlights

• 🧹 Automatic CUDA Memory Cleanup: Calls torch.cuda.empty_cache() after every test run to prevent GPU memory accumulation that could freeze the daemon.
• ⏱️ Stuck Detection & Warning: Automatically warns the user if test output is silent for more than 30 seconds, preventing confusion when tests appear stuck.
• 🛡️ Worker Subprocess Isolation: Tests run in a dedicated worker subprocess. Even if the worker crashes (OOM, deadlock), the daemon stays stable and auto-restarts the worker.

System Architecture

graph TD
    Client["Client CLI"] -->|HTTP over UDS/TCP| App["FastAPI App"]
    subgraph "Daemon Process"
        App --> Service["TestService"]
        Service -->|Atomic Lock| Service
        Service --> Runner["TestRunner (Worker Manager)"]
    end
    subgraph "Worker Subprocess (Isolated)"
        Worker["worker_main.py"] --> Nuke["NukeStrategy + CUDA Cleanup"]
        Nuke -->|Module Unloading| PySys[sys.modules]
        Worker -->|"pytest.main()"| Tests["User Tests"]
    end
    Runner -->|Spawn / Manage / Restart| Worker
    App -.-> Status["status.json"]
    Client -.-> Status

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Test Execution Flow

sequenceDiagram
    participant C as "Client CLI"
    participant S as "status.json"
    participant D as "Daemon (FastAPI)"
    participant R as "TestRunner"
    participant W as "Worker Subprocess"

    C->>S: Read status
    alt Daemon not running
        C->>D: Start Daemon (subprocess)
        D->>D: Acquire daemon.lock
        D->>D: Start Uvicorn
        D->>S: Write status
        C->>S: Poll until ready
    end

    C->>D: POST /v1/test/run/stream
    activate D
    D->>D: Acquire test_lock (asyncio)
    D->>R: run_tests(args)
    activate R
    R->>R: Lazy-spawn Worker (if not running)
    activate W
    Note over W: Worker pre-loads heavy deps<br/>(torch, transformers, ...)
    W-->>R: {"type": "ready"}
    R->>W: {"type": "run_test", args, nuke}
    W->>W: NukeStrategy
    W->>W: torch.cuda.empty_cache()
    W->>W: pytest.main() (captured output)
    W-->>R: Streaming output (JSON Lines)
    Note over R: Stuck detection: warn user<br/>after 30s of silence
    R-->>D: Streaming output
    D-->>C: Stream results
    deactivate W
    deactivate R
    deactivate D
    C->>C: Print output & exit

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📦 Installation

pip install sprintest

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📖 Quick Start

1. Run a test: Simply run stest followed by your test file. If the daemon isn't running, it will start automatically.

   stest tests/test_model_loading.py

2. Check Daemon status:

   stest status

3. Stop the Daemon:

   stest stop

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⚙️ Configuration

Environment Variables & Isolation

• SPRINTEST_TARGET_PKG: The name of the package you are developing. Sprintest will prioritize hot-reloading this package.
• SPRINTEST_FORCE_TCP: Set to 1 to bypass Unix Sockets and force TCP communication.
• SPRINTEST_PORT: Customize the TCP port (default: 8000).
• SPRINTEST_DIR: Override the default .sprintest directory (useful for multi-project isolation or CI environments).
• SPRINTEST_LOCK_FILE: Override the daemon lock file path.
• SPRINTEST_LOG_LEVEL: Set log level (DEBUG, INFO, WARNING, ERROR).

Advanced: pyproject.toml

You can prevent specific modules from being "nuked" during hot-reload by adding them to the ignore list:

[tool.sprintest]
ignore = [
    "torch.*",
    "transformers.*",
    "heavy_module_to_keep"
]

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🧪 Testing the Runner

Standard Unit Tests

uv run pytest tests

Self-Hosting (Bootstrap) Test

Sprintest can reliably run its own test suite through its own daemon to verify infrastructure stability:

stest tests

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📄 License

MIT License. See LICENSE for details.