MockingImposter.cs

public class ProductsImposter : IImposter
{
    public Imposter Build()
    {
        return new ImposterDefinition("ProductsMock")
                .DeclareResource("/api/Products", HttpMethod.Post)
                .When(r => r.Content.Contains("Name:Test product"))
                .Then(new ProductResponseCreator())
                .Build();
    }
}

public class ProductResponseCreator: IResponseCreator
{
    public Response CreateResponse()
    {
        var productCreatedResponse = new ProductCreatedResponse
                                   {
                                       Message = "Product created.",
                                       ProductId = (uint)new Random().Next(int.MaxValue)
                                   };

        return new ResponseBuilder().WithContent(productCreatedResponse, new JsonContentSerializer())
                                    .WithStatusCode(HttpStatusCode.Created)
                                    .Build();
    }
}