Limitations

Imposter keeps the source generator and runtime focused on common impersonation scenarios. This comes with a few intentional limitations.

Language and tooling

• Minimum supported C# version is 9.0.
• Only Roslyn-based C# projects are supported (no Visual Basic or F#).

Class targets

• Only non-sealed classes can be impersonated.
• Only virtual or abstract members can be impersonated on class imposters.
• UseBaseImplementation() applies only to non-abstract, virtual class members and is not available for interfaces.

Async behavior

• Async methods without setup return default, which for Task is null.
• Sequenced async outcomes are consumed in order; when a sequence is exhausted, the last outcome is repeated (where applicable).

Generated code

• Generated .g.cs files are implementation details and should not be edited directly; customize behavior via setups or by changing generator inputs.

Next steps

• Getting Started
• Key API Reference
• Base Implementation
• Cheat Sheet