Async Grammars Edit on GitHub

Storyteller was originally conceived and built in that more innocent time where most of your code was completely synchronous and multi-threading was somewhat rare. Flash forward to today, and we're all writing a lot more asynchronous code than ever before and it was time for Storyteller to get with the program.

To that end, Storyteller now allows you to build grammars that return Task objects, and Storyteller will take care of handling the Task within the execution pipeline so you don't have to. Right now the only options for asynchronous grammars are Sentence grammars.

Below is a sample from the forthcoming ASP.Net Core application extensions for Storyteller that exercises a "Hello, World" HTTP endpoint:

public class FakeFixture : AspNetCoreFixture
    [FormatAs("The response text from {url} should be '{contents}'")]
    public async Task<string> TheContentsShouldBe(string url)
        var result = await Scenario(_ =>

        return result.ResponseBody.ReadAsText().Trim();

As of right now (4.0), Storyteller supports methods that return:

  • Task to perform an action asynchronously
  • Task<bool> for asynchronous Fact grammars
  • Task<T> where "T" is an expected value that you want to assert upon