Testing Plugin Architectures in C#: Strategies for Extensible Systems

A layered testing strategy for C# plugin architectures covering three distinct test types: unit tests for concrete plugin implementations, contract tests using abstract xUnit base classes to enforce interface invariants across all plugins, and integration tests using AssemblyLoadContext to verify the full load-discover-execute pipeline. Also covers testing plugin discovery logic with interface extraction and fake directories, failure scenario testing for misbehaving plugins, and versioning/compatibility testing across contract versions. Includes a recommended project structure separating fast unit tests from slower integration tests.