State Sharing (Global State)

In complex test suites, you often need to share state across different phases of the test run—for example, initializing a database connection string in a global hook and accessing it within your tests.

Prova provides the TestContext.GlobalState property (backed by a thread-safe StateBag) to facilitate this.

How it Works

TestContext.GlobalState is a static singleton available throughout the entire lifecycle of the test runner. You can set values during initialization (e.g., in [BeforeAssembly]) and retrieve them in your tests.

Usage

1. Setting State (e.g., in a Hook)

using Prova;

public class GlobalSetup
{
    [BeforeAssembly]
    public static void Initialize()
    {
        // Calculate or retrieve expensive data once
        var connectionString = "Server=myServerAddress;Database=myDataBase;";
        
        // Store it globally
        TestContext.GlobalState.Set("ConnectionString", connectionString);
        TestContext.GlobalState.Set("StartTime", DateTime.Now);
    }
}

2. Accessing State (in a Test)

using Prova;

public class DatabaseTests
{
    [Fact]
    public void VerifyConnection()
    {
        // Retrieve the data safely
        var connStr = TestContext.GlobalState.Get<string>("ConnectionString");
        
        Assert.StartsWith("Server=", connStr);
    }

    [Fact]
    public void CheckTime()
    {
        // TryGet pattern avoids exceptions if key is missing
        if (TestContext.GlobalState.TryGet<DateTime>("StartTime", out var time))
        {
            Console.WriteLine($"Test run started at: {time}");
        }
    }
}

API Reference

The StateBag provides the following thread-safe methods:

• void Set<T>(string key, T value): Adds or updates a key.
• T Get<T>(string key): Retrieves a value. Throws KeyNotFoundException if missing.
• bool TryGet<T>(string key, out T? value): Safely attempts to retrieve a value.
• object? this[string key]: Indexer for direct access (returns object?).

Best Practices

1. Immutability: Ideally, store immutable objects (strings, configuration records) in the Global State to avoid side effects from parallel tests modifying the same object.
2. Thread Safety: StateBag itself is thread-safe, but the objects you store in it might not be. If multiple tests modify a stored object simultaneously, you must ensure that object is thread-safe.
3. Cleanup: You can use [AfterAssembly] to clean up resources stored in the Global State if necessary.