promises-arrow/src/DeferredPromise.micro.ts

`promises-arrow` is a library of (1) higher order functions, such as `map()` and `filter()`where the function returns a Promisel (2) Functions that wait, returning a Promise; (3) Functions that manage retrying an operation N times until it succeeds; (4,5)

import {assertThat} from "mismatched";
import {promises} from "./promises";

describe("DeferredPromise:", () => {
    it("resolve()s", () => {
        const defer = promises.deferredPromise<number>();
        const promise = defer.promise;
        setTimeout(() =>
            defer.resolve(3), 2);
        return promise.then(() => "OK")
    });

    it("rejects()s", () => {
        const defer = promises.deferredPromise<number>();
        const promise = defer.promise;
        setTimeout(() =>
            defer.reject("error"), 2);
        return promise.catch(e => assertThat(e).is("error"))
    });
});