Function "Returns a subscription object"

test/subscribe.js:127–163

(test, { Observable })

    },

    "Returns a subscription object" (test, { Observable }) {

        let called = 0;
        let subscription = new Observable(observer => {
            return _=> called++;
        }).subscribe({});

        let proto = Object.getPrototypeOf(subscription);

        testMethodProperty(test, proto, "unsubscribe", {
            configurable: true,
            writable: true,
            length: 0,
        });

        testMethodProperty(test, proto, "closed", {
            get: true,
            configurable: true,
            writable: true,
            length: 0,
        });

        test
        ._("Subscribe returns an object")
        .equals(typeof subscription, "object")
        ._("Contructor property is Object")
        .equals(subscription.constructor, Object)
        ._("closed property returns false before unsubscription")
        .equals(subscription.closed, false)
        ._("Unsubscribe returns undefined")
        .equals(subscription.unsubscribe(), undefined)
        ._("Unsubscribe calls the cleanup function")
        .equals(called, 1)
        ._("closed property is true after calling unsubscribe")
        .equals(subscription.closed, true)
        ;
    },

    "Cleanup function" (test, { Observable }) {