PagesTest.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.api.core;

import com.google.common.collect.Lists;

import org.testng.annotations.BeforeSuite;
import org.testng.annotations.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static org.mockito.Matchers.anyInt;
import static org.mockito.Matchers.anyLong;
import static org.mockito.Mockito.spy;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertFalse;
import static org.testng.Assert.assertTrue;

/**
 * Tests {@link Pages}.
 *
 * @author Yevhenii Voevodin
 */
public class PagesTest {

    private TestPagesSupplier testSource;

    @BeforeSuite
    private void setUp() {
        String[] strings = new String[10];
        for (int i = 0; i < strings.length; i++) {
            strings[i] = "test-string-" + i;
        }
        testSource = new TestPagesSupplier(strings);
    }

    @Test
    public void eagerlyStreamsAllElements() {
        List<String> result = Pages.stream(testSource::getStrings, 2).collect(Collectors.toList());

        assertEquals(result, testSource.strings);
    }

    @Test
    public void eagerlyIteratesAllElements() {
        ArrayList<String> result = Lists.newArrayList(Pages.iterate(testSource::getStrings, 2));

        assertEquals(result, testSource.strings);
    }

    @Test
    public void lazyStreamsAllElements() {
        List<String> result = Pages.streamLazily(testSource::getStrings, 2).collect(Collectors.toList());

        assertEquals(result, testSource.strings);
    }

    @Test
    public void lazyIteratesAllElements() {
        ArrayList<String> result = Lists.newArrayList(Pages.iterateLazily(testSource::getStrings, 2));

        assertEquals(result, testSource.strings);
    }

    @Test
    public void lazyStreamingDoesNotPollNextPageUntilNeeded() {
        TestPagesSupplier src = spy(new TestPagesSupplier("string1", "string2", "string3"));

        assertTrue(Pages.streamLazily(src::getStrings, 1).anyMatch(s -> s.equals("string2")));

        verify(src, times(2)).getStrings(anyInt(), anyLong());
        verify(src).getStrings(1, 0);
        verify(src).getStrings(1, 1);
    }

    @Test
    public void lazyIteratingDoesNotPollNextPageUntilNeeded() {
        TestPagesSupplier src = spy(new TestPagesSupplier("string1", "string2", "string3"));

        Iterator<String> it = Pages.iterateLazily(src::getStrings, 1).iterator();
        it.next();
        it.next();

        verify(src, times(2)).getStrings(anyInt(), anyLong());
        verify(src).getStrings(1, 0);
        verify(src).getStrings(1, 1);
    }

    @Test
    public void returnsEmptyStreamWhenFetchingEagerly() {
        Stream<String> stream = Pages.stream(new TestPagesSupplier()::getStrings);

        assertFalse(stream.findAny().isPresent());
    }

    @Test
    public void returnsIterableWithNoElementsWhileFetchingEagerly() {
        Iterator<String> it = Pages.iterate(new TestPagesSupplier()::getStrings).iterator();

        assertFalse(it.hasNext());
    }

    @Test
    public void returnsEmptyStreamWhenFetchingLazily() {
        Stream<String> stream = Pages.streamLazily(new TestPagesSupplier()::getStrings);

        assertFalse(stream.findAny().isPresent());
    }

    @Test
    public void returnsIterableWithNoeElementsWhileFetchingLazily() {
        Iterator<String> it = Pages.iterateLazily(new TestPagesSupplier()::getStrings).iterator();

        assertFalse(it.hasNext());
    }

    private static class TestPagesSupplier {

        private final List<String> strings;

        private TestPagesSupplier(String... strings) {
            this.strings = Arrays.asList(strings);
        }

        public Page<String> getStrings(int max, long skip) {
            List<String> items = strings.stream()
                                        .skip(skip)
                                        .limit(max)
                                        .collect(Collectors.toList());
            return new Page<>(items, skip, max, strings.size());
        }
    }
}