dubc-ds-test

Utility for testing observable data structures.

$ npm install -D dubc-ds-test

In your tests, you can use the capture function to quickly test that your data structure is emitting the correct events.

The capture function takes two arguments, a keeper object for the listener and the data structure you want to capture. The data structure must be a subclass of the Base class from dubc-ds-base.

The capture function assigns a listener to the data structure that simply records the events it fires. The iterables for event.added.items and event.deleted.items are turned into arrays, so you can simply use toStrictEqual to ensure the captured events are expected.

The capture function returns an object with three methods:

• only: This throws an error if there isn't exactly one recorded event. Otherwise it returns the one event and clears the recorded list.
• all: This returns an array of all of the recorded events and clears the recorded events.
• clear: This clears the recorded events without returning anything.

Example usage:

import { capture } from "dubc-ds-test"

const K = {} // keeper object

let ds = new MyDS()
let c = capture(K, ds)
beforeEach(() => {
  ds = new MyDS([1, 2, 3, 4, 5])
  c = capture(K, ds)
  // eliminate the initial fire, which generally isn't interesting:
  c.clear()
})
test("clear", () => {
  ds.clear()
  expect(c.only()).toStrictEqual({cleared:5})
})
test("add", () => {
  ds.add(6)
  expect(c.only()).toStrictEqual({added:{items:[6], at:5}})
})