aspire-integration-testing

name	aspire-integration-testing
description	Patterns for integration testing Aspire-hosted .NET services with WebApplicationFactory, Testcontainers, and SQLite
domain	testing
confidence	medium
source	earned

Context

When writing integration tests for .NET Aspire services that use AddNpgsqlDbContext and AddRedisClient (or similar Aspire component methods). Applies to any service using Aspire 13.x with PostgreSQL + Redis.

Patterns

• Use WebApplicationFactory<Program> to host the service under test — avoids Aspire AppHost orchestration in tests
• Aspire component methods (AddNpgsqlDbContext, AddRedisClient) validate connection strings at registration time — provide fake connection strings via builder.UseSetting("ConnectionStrings:name", "...") in ConfigureWebHost
• Swap Npgsql for SQLite in-memory by removing ALL EF Core and Npgsql service descriptors (match by FullName containing "EntityFramework", "Npgsql", "DbContext") then re-registering with AddDbContext<T>(o => o.UseSqlite(...))
• SQLite in-memory with Cache=Shared requires a keep-alive SqliteConnection that stays open for the entire fixture lifetime
• Create the schema via EnsureCreatedAsync() during fixture initialization, before the host starts
• Use Testcontainers Redis for real pub/sub testing — mocking ISubscriber.OnMessage callbacks is brittle
• Implement IAsyncLifetime on the factory class for container lifecycle (note: xUnit IAsyncLifetime uses Task, not ValueTask)
• Use IClassFixture<BridgeApiFactory> to share the factory across tests in a class — avoids container churn

Examples

// Keep-alive connection pattern for SQLite in-memory
private SqliteConnection _keepAlive = null!;
_keepAlive = new SqliteConnection(connStr);
await _keepAlive.OpenAsync();
// ... in DisposeAsync: await _keepAlive.DisposeAsync();

// Removing Aspire-registered services
var toRemove = services.Where(d => {
    var st = d.ServiceType.FullName ?? "";
    return st.Contains("EntityFramework", OrdinalIgnoreCase)
        || st.Contains("Npgsql", OrdinalIgnoreCase)
        || st.Contains("DbContext", OrdinalIgnoreCase);
}).ToList();
foreach (var d in toRemove) services.Remove(d);

// Provider-agnostic Max query (works on both Npgsql and SQLite)
var maxIndex = await db.Items.Select(x => (int?)x.Index).MaxAsync();
var nextIndex = (maxIndex ?? -1) + 1;

Anti-Patterns

• Don't use DefaultIfEmpty(value).MaxAsync() — SQLite provider can't translate it
• Don't forget to provide connection strings before Aspire components register — they validate eagerly
• Don't use BuildServiceProvider() inside ConfigureServices to call EnsureCreated() — it creates a separate DI container with stale registrations
• Don't close the SQLite keep-alive connection before the test host shuts down — the in-memory database disappears
• Don't try to partially remove Npgsql services — EF Core detects multiple providers if any Npgsql registrations remain