In Tests and CI

Share a server with a fixture

Starting a server takes about a second once the binaries are cached, so share one across the tests in a class (or a whole assembly) with a fixture. This is xUnit v3, where IAsyncLifetime returns ValueTask; with xUnit v2, return Task from both methods instead:

public sealed class DatabaseFixture : IAsyncLifetime
{
    public PgServer Server { get; } = new("17");

    public async ValueTask InitializeAsync() => await Server.StartAsync();

    public async ValueTask DisposeAsync() => await Server.DisposeAsync();
}

public class BookTests(DatabaseFixture db) : IClassFixture<DatabaseFixture>
{
    [Fact]
    public async Task Connects()
    {
        await using var conn = new NpgsqlConnection(db.Server.ConnectionString);
        await conn.OpenAsync();
        // ...
    }
}

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For a whole assembly, use an assembly fixture ([assembly: AssemblyFixture(typeof(DatabaseFixture))] in xUnit v3) or a collection fixture. Keep tests independent by giving each its own database or schema, or by rolling back a transaction at the end of each test.

Reuse a server across runs

A named instance keeps running between test runs when you start it yourself, for example with the pgembed CLI (pgembed start app --version 17). Tests then attach to it in milliseconds and leave it running.

In CI

• Cache the binaries. Set PGEMBED_CACHE_DIR to a folder your CI caches between runs, or set BinariesDir, so the first test does not pay for the download.
• Warm the cache in its own step with InstallAsync(), so download time shows up there and not in a test's timeout.
• Run as a regular user. Postgres refuses to run as root; in a container, add a user.
• Windows agents may need AddLocalUserAccessPermission = true; see Troubleshooting.