import * as B from "."
import { valueEvent, Event } from "./abstractions"
import { nop } from "./util"

describe("Property", () => {
  it("scan", () => {
    const b = B.bus<number>()
    const op = B.scan(0, (a: number, b: number) => a + b, B.globalScope)
    const prop = b.pipe(op)
    const values: number[] = []
    const valuesChange: number[] = []
    prop.forEach((v) => values.push(v))
    prop.onChange((v) => valuesChange.push(v), nop)
    expect(values).toEqual([0])
    expect(valuesChange).toEqual([])
    b.push(1)
    expect(values).toEqual([0, 1])
    expect(valuesChange).toEqual([1])
    b.push(1)
    expect(values).toEqual([0, 1, 2])
    expect(valuesChange).toEqual([1, 2])
  })
})