# Better Testing Strategy - Code Samples

Source advisory: `docs/product-advisories/22-Dec-2026 - Better testing strategy.md`  
Note: These samples are carried over verbatim for reference and should remain offline-friendly and deterministic.

## Minimal primitives to standardize immediately
```csharp
public static class TestCategories
{
    public const string Unit = "Unit";
    public const string Property = "Property";
    public const string Snapshot = "Snapshot";
    public const string Integration = "Integration";
    public const string Contract = "Contract";
    public const string Security = "Security";
    public const string Performance = "Performance";
    public const string Live = "Live"; // opt-in only
}
```

## Property test example (FsCheck-style)
```csharp
using Xunit;
using FsCheck;
using FsCheck.Xunit;

public sealed class VersionComparisonProperties
{
    [Property(Arbitrary = new[] { typeof(Generators) })]
    [Trait("Category", "Unit")]
    [Trait("Category", "Property")]
    public void Compare_is_antisymmetric(SemVer a, SemVer b)
    {
        var ab = VersionComparer.Compare(a, b);
        var ba = VersionComparer.Compare(b, a);

        Assert.Equal(Math.Sign(ab), -Math.Sign(ba));
    }

    private static class Generators
    {
        public static Arbitrary<SemVer> SemVer() =>
            Arb.From(Gen.Elements(
                new SemVer(0,0,0),
                new SemVer(1,0,0),
                new SemVer(1,2,3),
                new SemVer(10,20,30)
            ));
    }
}
```

## Canonical JSON determinism assertion
```csharp
public static class DeterminismAssert
{
    public static void CanonicalJsonStable<T>(T value, string expectedSha256)
    {
        byte[] canonical = CanonicalJson.SerializeToUtf8Bytes(value); // your library
        string actual = Convert.ToHexString(SHA256.HashData(canonical)).ToLowerInvariant();
        Assert.Equal(expectedSha256, actual);
    }
}
```

## Postgres fixture skeleton (Testcontainers)
```csharp
public sealed class PostgresFixture : IAsyncLifetime
{
    public string ConnectionString => _container.GetConnectionString();

    private readonly PostgreSqlContainer _container =
        new PostgreSqlBuilder().WithImage("postgres:16").Build();

    public async Task InitializeAsync()
    {
        await _container.StartAsync();
        await ApplyMigrationsAsync(ConnectionString);
    }

    public async Task DisposeAsync() => await _container.DisposeAsync();

    private static async Task ApplyMigrationsAsync(string cs)
    {
        // call your migration runner for the module under test
    }
}
```

## OTel trace capture assertion
```csharp
public sealed class OtelCapture : IDisposable
{
    private readonly List<Activity> _activities = new();
    private readonly ActivityListener _listener;

    public OtelCapture()
    {
        _listener = new ActivityListener
        {
            ShouldListenTo = _ => true,
            Sample = (ref ActivityCreationOptions<ActivityContext> _) => ActivitySamplingResult.AllData,
            ActivityStopped = a => _activities.Add(a)
        };
        ActivitySource.AddActivityListener(_listener);
    }

    public void AssertHasSpan(string name) =>
        Assert.Contains(_activities, a => a.DisplayName == name);

    public void Dispose() => _listener.Dispose();
}
```