WebApplicationFactory vs Testcontainers for ASP.NET Core integration tests

They are not alternatives. WebApplicationFactory boots your app, Testcontainers boots your dependencies. Measured on .NET SDK 10.0.201: a container fixture costs 1.7 s per class against 10 ms for SQLite, and a HasMaxLength(16) violation that Postgres rejects with 22001 is silently accepted by SQLite.