How to test a function which returns a promise and uses async.waterfall() model inside the promise?

[laxmid]

I want to write test cases for the following function:

Function implementation contains:

function test(){
    return new promise(function(resolve, reject){
        async.waterfall([
		function1(cb){
			....
		},
		function2(cb){
			....
		},
		function3(cb){
			.....
		}
	]);
   });
}

I have tried writing test cases in following ways:

1. Using callback:

describe('test method', function(){
	it('Should return failed', function(done){
		test().should.eventually.be.rejected.and.have.property('code','Failed');
		done();
	});
});

In this case, the test cases passed but got the error "Unhandled rejection AssertionError" for every test case.

2. Using async-await:

describe('test method', function(){
	it('Should return failed',async function(){
		var result = await test();
		result.should.eventually.be.rejected.and.have.property('code','Failed');
		return;
	});
});`

In this case, I got the error "ReferenceError: regeneratorRuntime is not defined".

Is there any other way for this? Any suggestions?