java-tutorials/rxjava/src/test/java/com/baeldung/rxjava/ObservableUnitTest.java

package com.baeldung.rxjava;

import org.junit.Test;
import rx.Observable;

import static com.baeldung.rxjava.ObservableImpl.getTitle;
import static junit.framework.Assert.assertTrue;

public class ObservableUnitTest {

    private String result = "";

    @Test
    public void givenString_whenJustAndSubscribe_thenEmitsSingleItem() {
        Observable<String> observable = Observable.just("Hello");
        observable.subscribe(s -> result = s);
        assertTrue(result.equals("Hello"));
    }

    @Test
    public void givenArray_whenFromAndSubscribe_thenEmitsItems() {
        String[] letters = {"a", "b", "c", "d", "e", "f", "g"};
        Observable<String> observable = Observable.from(letters);
        observable.subscribe(
          i -> result += i,
          Throwable::printStackTrace,
          () -> result += "_Complete"
        );
        assertTrue(result.equals("abcdefg_Complete"));
    }

    @Test
    public void givenArray_whenConvertsObservabletoBlockingObservable_thenReturnFirstElement() {
        String[] letters = {"a", "b", "c", "d", "e", "f", "g"};
        Observable<String> observable = Observable.from(letters);
        String blockingObservable = observable.toBlocking().first();

        observable.subscribe(
          i -> result += i,
          Throwable::printStackTrace,
          () -> result += "_Completed"
        );
        assertTrue(String.valueOf(result.charAt(0)).equals(blockingObservable));
    }

    @Test
    public void givenArray_whenMapAndSubscribe_thenReturnCapitalLetters() {
        String[] letters = {"a", "b", "c", "d", "e", "f", "g"};

        Observable.from(letters)
          .map(String::toUpperCase)
          .subscribe(letter -> result += letter);

        assertTrue(result.equals("ABCDEFG"));
    }

    @Test
    public void givenArray_whenFlatMapAndSubscribe_thenReturnUpperAndLowerCaseLetters() {

        Observable.just("book1", "book2")
          .flatMap(s -> getTitle())
          .subscribe(l -> result += l);

        assertTrue(result.equals("titletitle"));
    }

    @Test
    public void givenArray_whenScanAndSubscribe_thenReturnTheSumOfAllLetters() {
        String[] letters = {"a", "b", "c"};

        Observable.from(letters)
          .scan(new StringBuilder(), StringBuilder::append)
          .subscribe(total -> result += total.toString());

        assertTrue(result.equals("aababc"));
    }

    @Test
    public void givenArrayOfNumbers_whenGroupBy_thenCreateTwoGroupsBasedOnParity() {
        Integer[] numbers = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        String[] EVEN = {""};
        String[] ODD = {""};

        Observable.from(numbers)
          .groupBy(i -> 0 == (i % 2) ? "EVEN" : "ODD")
          .subscribe(group ->
            group.subscribe((number) -> {
                if (group.getKey().equals("EVEN")) {
                    EVEN[0] += number;
                } else {
                    ODD[0] += number;
                }
            })
          );

        assertTrue(EVEN[0].equals("0246810"));
        assertTrue(ODD[0].equals("13579"));
    }

    @Test
    public void givenArrayOfNumbers_whenFilter_thenGetAllOddNumbers() {
        Integer[] numbers = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        Observable.from(numbers)
          .filter(i -> (i % 2 == 1))
          .subscribe(i -> result += i);

        assertTrue(result.equals("13579"));
    }

    @Test
    public void givenEmptyObservable_whenDefaultIfEmpty_thenGetDefaultMessage() {

        Observable.empty()
          .defaultIfEmpty("Observable is empty")
          .subscribe(s -> result += s);

        assertTrue(result.equals("Observable is empty"));
    }

    @Test
    public void givenObservableFromArray_whenDefaultIfEmptyAndFirst_thenGetFirstLetterFromArray() {
        String[] letters = {"a", "b", "c", "d", "e", "f", "g"};

        Observable.from(letters)
          .defaultIfEmpty("Observable is empty")
          .first()
          .subscribe(s -> result += s);

        assertTrue(result.equals("a"));
    }

    @Test
    public void givenObservableFromArray_whenTakeWhile_thenGetSumOfNumbersFromCondition() {
        Integer[] numbers = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        final Integer[] sum = {0};

        Observable.from(numbers)
          .takeWhile(i -> i < 5)
          .subscribe(s -> sum[0] += s);

        assertTrue(sum[0] == 10);
    }
}