Sequential Returns

Imposter supports sequencing multiple outcomes for the same method using Then(). This is useful for modeling stateful behavior across repeated calls.

Target type used in examples:

Example

using Imposter.Abstractions;

[assembly: GenerateImposter(typeof(Imposter.Tests.Docs.Methods.ISeqService))]

public interface ISeqService
{
    int GetNumber();
    System.Threading.Tasks.Task<int> GetNumberAsync();
}

Basic sequencing

Example

imposter.GetNumber()
    .Returns(1)
    .Then().Returns(2)
    .Then().Returns(3);

service.GetNumber(); // 1
service.GetNumber(); // 2
service.GetNumber(); // 3

Interleaving exceptions

You can interleave Throws within a sequence. Separate each step with Then().

Example

imposter.GetNumber()
    .Returns(1)
    .Then().Throws<InvalidOperationException>()
    .Then().Returns(2);

service.GetNumber(); // 1
service.GetNumber(); // throws InvalidOperationException
service.GetNumber(); // 2

Pro tip

• Always use Then() between distinct outcomes.
• Repeating Returns (or Throws) without Then() is invalid.
• You can mix Returns, ReturnsAsync, Throws, and UseBaseImplementation() across steps for class targets.

Concurrency note

Under concurrent calls, outcomes are consumed in order. When a sequence is exhausted, behavior falls back to the last applicable outcome or to default behavior (depending on the target and mode).