rxjs-marbles

rxjs-marbles

What is it?

rxjs-marbles is an RxJS marble testing library that should be compatible with any test framework. It wraps the RxJS TestScheduler and provides methods similar to the basic methods used in RxJS's marble tests.

It can be used with Jasmine, Mocha or Tape in the browser or in Node and it supports CommonJS and ES module bundlers.

Why might you need it?

I created this package because I wanted to use RxJS marble tests in a number of projects and those projects used different test frameworks.

There are a number of marble testing packages available - including the Mocha-based implementation in RxJS itself; although, much of that implementation is not part of the RxJS distribution - but I wanted something that was simple, didn't involve messing with globals and beforeEach/afterEach functions and was consistent across test frameworks.

If you are looking for something similar, this might suit.

Install

Install the package using NPM:

npm install rxjs-marbles --save-dev

And import the functions for use with TypeScript or ES2015:

import { marbles } from "rxjs-marbles";

Or require the module for use with Node or a CommonJS bundler:

const { marbles } = require("rxjs-marbles");

API

The rxjs-marbles API is comprised of two functions:

• configure
• marbles

configure

interface Configuration {
    assert?: (value: any, message: string) => void;
    assertDeepEqual?: (a: any, b: any) => void;
}

function configure(options: Configuration): void;

The configure method can be used to specify the assertion functions that are to be used. Calling it is optional; it's only necessary if particular assertion functions are to be used.

The default implementations simply perform the assertion and throw an error for failed assertions.

marbles

function marbles(test: (context: Context) => any): () => any;
function marbles<T1>(test: (context: Context, t1: T1) => any): (t1: T1) => any;
function marbles<T1, T2>(test: (context: Context, t1: T1, t2: T2) => any): (t1: T1, t2: T2) => any;
function marbles<T1, T2, T3>(test: (context: Context, t1: T1, t2: T2, t3: T3) => any): (t1: T1, t2: T2, t3: T3) => any;

marbles is passed the test function, which it wraps, passing the wrapper to the test framework. When the test function is called, it is passed the Context - which contains methods that correspond to the basic methods described in the RxJS documentation:

interface Context {
    cold<T = any>(marbles: string, values?: any, error?: any): ColdObservable<T>;
    configure(options: Configuration): void;
    equal<T = any>(actual: Observable<T>, expected: Observable<T>): void;
    expect<T = any>(actual: Observable<T>): Expect<T>;
    flush(): void;
    has<T = any>(actual: Observable<T>, expected: string | string[]): void;
    hot<T = any>(marbles: string, values?: any, error?: any): HotObservable<T>;
    readonly scheduler: TestScheduler;
    time(marbles: string): number;
}

interface Expect<T> {
    toBeObservable(expected: ColdObservable<T> | HotObservable<T>): void;
    toHaveSubscriptions(expected: string | string[]): void;
}

Usage with Jasmine and Mocha

Instead of passing your test function directly to it, pass it to the library's marbles function, like this:

import { marbles } from "rxjs-marbles";

it("should map the values", marbles((m) => {

    const values = {
        a: 1,
        b: 2,
        c: 3,
        d: 4
    };

    const source =  m.hot("--^-a-b-c-|", values);
    const subs =            "^-------!";
    const expected = m.cold("--b-c-d-|", values);

    const destination = source.map((value) => value + 1);
    m.expect(destination).toBeObservable(expected);
    m.expect(source).toHaveSubscriptions(subs);
}));

Usage with Tape

As with Jasmine and Mocha, instead of passing your test function directly to Tape, pass it to the library's marbles function. The marbles function will concatenate the additional Test argument it receives from Tape.

There is a /tape directory in the package that includes wrapper that will correctly type additional argument and will call configure - passing Tape's assertion methods to ensure marble assertions will be counted towards Tape's plan - so be sure to specify rxjs-marbles/tape in the import statement or require call:

import * as tape from "tape";
import { marbles } from "rxjs-marbles/tape";

tape("it should map the values", marbles((m, t) => {

    t.plan(2);

    const values = {
        a: 1,
        b: 2,
        c: 3,
        d: 4
    };

    const source =  m.hot("--^-a-b-c-|", values);
    const subs =            "^-------!";
    const expected = m.cold("--b-c-d-|", values);

    const destination = source.map((value) => value + 1);
    m.expect(destination).toBeObservable(expected);
    m.expect(source).toHaveSubscriptions(subs);
}));

If the BDD syntax is something you really don't like, there are some alternative methods on the Context that are more Tape-ish:

const destination = source.map((value) => value + 1);
m.equal(destination, expected);
m.has(source, subs);

Changelog

1.3.1 (2017-07-22)

Documentation

• Correct missing plan call in Tape example. (7400890)

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