Test the concept that if first Observable doesn't contain satisfactory value then try the next one.

ObservableFlatMapTest.groovy

package com.charter.aesd.deviceactivation.middle.services

import rx.Observable
import rx.functions.Func1
import spock.lang.Specification

/**
 * Created by rhasija on 10/28/15.
 */
class ObservableTest extends Specification {
    def "happy path"() {


        given:
        def observable1 = Observable.just(Optional.of(1))
        def observable2 = Observable.just(Optional.of(2))
        def observable3 = Observable.just(Optional.of(3))

        when:
        def single = observable1.flatMap(new Func1<Optional<Integer>, Observable<? extends Optional<Integer>>>() {
            @Override
            Observable<? extends Optional<Integer>> call(Optional<Integer> integer) {
                if (integer.get() != 1) {
                    return integer
                } else {
                    return observable2
                }
            }
        }).flatMap(new Func1<Optional<Integer>, Observable<? extends Optional<Integer>>>() {
            @Override
            Observable<? extends Optional<Integer>> call(Optional<Integer> integer) {
                if (integer.get() != 2)
                    return integer
                else
                    return observable3
            }
        }).toBlocking().single()

        then:
        single.isPresent()
        single.get() == 3
    }
}