Action

Action is a function that emits events. It may have a callback or be empty. Actions are useful for triggering scenarios or controlling async flows.

Return value

Action returns a promise which is resolved after callback is finished and all event listeners got notified. If action callback returns a value, promise is resolved with that value.

Properties

• config - resolved config
• events - record of AwaiEvent events

Events:

• invoked - emits ActionInvokedEvent when action is called
• fulfilled - emits ActionFulfilledEvent when action is finished successfully
• rejected - emits ActionRejectedEvent when callback throws or returns a rejected promise

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Example action

const increment = action(() => counter.set(current => current + 1));

setTimeout(increment, 100);

await increment.events.invoked;

console.log(`incremented after 100ms`);

Empty actions

Actions may be empty. When that's the case, they only emit invoked event.

Using empty actions to control scenarios

const increment = action();

scenario(increment.events.invoked, () => {
  counter.set(current => current + 1);
});

Empty actions can still receive arguments which will be available in event payloads. If you use TypeScript, you can specify arguments types:

Passing arguments to an empty action in order to have better control over scenario

const createTask = action<[title: string, description: string]>();

scenario(createTask.events.invoked, (event) => {
  const [title, description] = event.arguments;
  // handle task creation
});

createTask('Task title', 'Task description');

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Types

Source

type ActionInvokedEvent<Args> = {
  arguments: Args;
  config: Config;
};

type ActionFulfilledEvent<Args, Return> = {
  arguments: Args;
  config: Config;
  result: Return;
};

type ActionRejectedEvent<Args> = {
  arguments: Args;
  config: Config;
  error: unknown;
};

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