RxJs 5 ascii marbles output for failing test - unit-testing

Question

I am learning RxJS 5 (release candidate). I am using the ASCII marble diagrams in unit tests.
For a failing test, is there a built in function to show the actual ASCII marbles string instead of the deep equal failure result? It seems like if I have to understand and write an expected ASCII marble string that it would be useful for a failing test to show the actual ASCII marble string. It would assist in troubleshooting.
I am hoping that there is a built in function that is effectively the reverse of parseMarbles(). I have not found anything yet when searching through the documentation and source code.
Below is an example taken from Writing marble tests - anatomy of a test that I modified to get a failing test. It gives the following output:
AssertionError: expected [ Array(5) ] to deeply equal [ Array(4) ]Error
I would rather see something like:
AssertionError: expected "'---(be)----c-f-----|'"
to equal "'---(be)----c-------|'"
http://jsbin.com/hipepew/edit?js,output
mocha.setup('bdd');
const expect = chai.expect;
describe('RXJS 5 Marbles', () => {
it("basic anatomy of a failing test", () => {
const rxTestScheduler: TestScheduler = new Rx.TestScheduler(function (actual, expected) {
expect(actual).to.deep.equal(expected);
});
const e1 = rxTestScheduler.createHotObservable<string>('----a--^--b-------c--|');
const e2 = rxTestScheduler.createHotObservable<string>('---d-^--e---------f-----|');
const expectedFail = '---(be)----c-------|';//missing f at frame 130
rxTestScheduler.expectObservable(e1.merge(e2)).toBe(expectedFail);
rxTestScheduler.flush();
});
});
mocha.run();