ObservableFactoriesExample.java

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 * Copyright (c) 2015 Christos Froussios
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package itrx.chapter2.creating;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.util.Arrays;
import java.util.concurrent.TimeUnit;

import org.junit.Test;

import rx.Observable;
import rx.observers.TestSubscriber;
import rx.schedulers.Schedulers;
import rx.schedulers.TestScheduler;

public class ObservableFactoriesExample {

	public void exampleJust() {
		Observable<String> values = Observable.just("one", "two", "three");
		values.subscribe(
		    v -> System.out.println("Received: " + v),
		    e -> System.out.println("Error: " + e),
		    () -> System.out.println("Completed")
		); 
		
		// Received: one
		// Received: two
		// Received: three
		// Completed
	}
	
	public void exampleEmpty() {
		Observable<String> values = Observable.empty();
		values.subscribe(
		    v -> System.out.println("Received: " + v),
		    e -> System.out.println("Error: " + e),
		    () -> System.out.println("Completed")
		);
		
		// Completed
	}
	
	public void exampleNever() {
		Observable<String> values = Observable.never();
		values.subscribe(
		    v -> System.out.println("Received: " + v),
		    e -> System.out.println("Error: " + e),
		    () -> System.out.println("Completed")
		);
	}
	
	public void exampleError() {
		Observable<String> values = Observable.error(new Exception("Oops"));
		values.subscribe(
		    v -> System.out.println("Received: " + v),
		    e -> System.out.println("Error: " + e),
		    () -> System.out.println("Completed")
		);
		
		// Error: java.lang.Exception: Oops
	}
	
	public void exampleShouldDefer() throws InterruptedException {
		Observable<Long> now = Observable.just(System.currentTimeMillis());

		now.subscribe(System.out::println);
		Thread.sleep(1000);
		now.subscribe(System.out::println);
		
		// 1431443908375
		// 1431443908375
	}
	
	public void exampleDefer() throws InterruptedException {
		Observable<Long> now = Observable.defer(() ->
        	Observable.just(System.currentTimeMillis()));

		now.subscribe(System.out::println);
		Thread.sleep(1000);
		now.subscribe(System.out::println);
		
		// 1431444107854
		// 1431444108858
	}
	
	public void exampleCreate() {
		Observable<String> values = Observable.create(o -> {
			o.onNext("Hello");
			o.onCompleted();
		});
		
		values.subscribe(
		    v -> System.out.println("Received: " + v),
		    e -> System.out.println("Error: " + e),
		    () -> System.out.println("Completed")
		);
		
		// Received: Hello
		// Completed
	}
	
	
	//
	// Tests
	//
	
	@Test
	public void testJust() {
		TestSubscriber<String> tester = new TestSubscriber<String>();
		
		Observable<String> values = Observable.just("one", "two", "three");
		values.subscribe(tester);
		
		tester.assertReceivedOnNext(Arrays.asList("one", "two", "three"));
		tester.assertNoErrors();
		tester.assertTerminalEvent();
	}
	
	@Test
	public void testEmpty() {
		TestSubscriber<String> tester = new TestSubscriber<String>();
		
		Observable<String> values = Observable.empty();
		values.subscribe(tester);
		
		tester.assertReceivedOnNext(Arrays.asList());
		tester.assertNoErrors();
		tester.assertTerminalEvent();
	}
	
	@Test
	public void testNever() {
		TestSubscriber<String> tester = new TestSubscriber<String>();
		
		Observable<String> values = Observable.never();
		values.subscribe(tester);
		
		tester.assertReceivedOnNext(Arrays.asList());
		tester.assertNoErrors();
		assertEquals(tester.getOnCompletedEvents().size(), 0);
	}
	
	@Test
	public void testError() {
		TestSubscriber<String> tester = new TestSubscriber<String>();
		
		Observable<String> values = Observable.error(new Exception("Oops"));
		values.subscribe(tester);
		
		tester.assertReceivedOnNext(Arrays.asList());
		tester.assertTerminalEvent();
		assertEquals(tester.getOnErrorEvents().size(), 1);
		assertEquals(tester.getOnCompletedEvents().size(), 0);
	}
	
	@Test
	public void testShouldDefer() throws InterruptedException {
		TestScheduler scheduler = Schedulers.test();
		TestSubscriber<Long> tester1 = new TestSubscriber<>();
		TestSubscriber<Long> tester2 = new TestSubscriber<>();
		
		Observable<Long> now = Observable.just(scheduler.now());

		now.subscribe(tester1);
		scheduler.advanceTimeBy(1000, TimeUnit.MILLISECONDS);
		now.subscribe(tester2);
		
		assertEquals(tester1.getOnNextEvents().get(0),
				tester2.getOnNextEvents().get(0));
	}
	
	@Test
	public void testDefer() {
		TestScheduler scheduler = Schedulers.test();
		TestSubscriber<Long> tester1 = new TestSubscriber<>();
		TestSubscriber<Long> tester2 = new TestSubscriber<>();
		
		Observable<Long> now = Observable.defer(() ->
			Observable.just(scheduler.now()));

		now.subscribe(tester1);
		scheduler.advanceTimeBy(1000, TimeUnit.MILLISECONDS);
		now.subscribe(tester2);
		
		assertTrue(tester1.getOnNextEvents().get(0) <
					tester2.getOnNextEvents().get(0));
	}
	
	@Test
	public void testCreate() {
		TestSubscriber<String> tester = new TestSubscriber<String>();
		
		Observable<String> values = Observable.create(o -> {
		    o.onNext("Hello");
		    o.onCompleted();
		});
		values.subscribe(tester);
		
		tester.assertReceivedOnNext(Arrays.asList("Hello"));
		tester.assertTerminalEvent();
		tester.assertNoErrors();
	}
}