CollectionUtilsTest.java

package vnet.sms.common.shell.springshell.internal.util;

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

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.junit.Test;

/**
 * Unit test of {@link CollectionUtils}
 * 
 * @author Andrew Swan
 * @since 1.2.0
 */
public class CollectionUtilsTest {

	// A simple filter for testing the filtering methods
	private static final Filter<String>	NON_BLANK_FILTER	= new Filter<String>() {
		                                                     @Override
		                                                     public boolean include(
		                                                             final String instance) {
			                                                     return StringUtils
			                                                             .hasText(instance);
		                                                     }
	                                                     };

	private static class Parent {
		@Override
		public String toString() {
			return getClass().getSimpleName();
		}
	}

	private static class Child extends Parent {
	}

	@Test
	public void testFilterNullCollection() {
		assertEquals(0, CollectionUtils.filter(null, NON_BLANK_FILTER).size());
	}

	@Test
	public void testFilterNonNullIterableWithNullFilter() {
		// Set up
		final Iterable<String> inputs = Arrays.asList("a", "");

		// Invoke
		final List<? extends String> results = CollectionUtils.filter(inputs,
		        null);

		// Check
		assertEquals(inputs, results);
	}

	@Test
	public void testFilterNonNullIterableWithNonNullFilter() {
		// Set up
		final Iterable<String> inputs = Arrays.asList("a", "", null, "b");

		// Invoke
		final List<? extends String> results = CollectionUtils.filter(inputs,
		        NON_BLANK_FILTER);

		// Check
		assertEquals(Arrays.asList("a", "b"), results);
	}

	@Test
	public void testAddNullCollectionToNullCollection() {
		assertFalse(CollectionUtils.addAll(null, null));
	}

	@Test
	public void testAddNullCollectionToNonNullCollection() {
		// Set up
		final Parent parent = new Parent();
		final Collection<Parent> parents = Arrays.asList(parent);

		// Invoke
		final boolean added = CollectionUtils.addAll(null, parents);

		// Check
		assertFalse(added);
	}

	@Test
	public void testAddNonNullCollectionToNonNullCollection() {
		// Set up
		final Parent parent = new Parent();
		final Child child = new Child();
		final Collection<Parent> parents = new ArrayList<Parent>();
		parents.add(parent);

		// Invoke
		final boolean added = CollectionUtils.addAll(Arrays.asList(child),
		        parents);

		// Check
		assertTrue(added);
		assertEquals(Arrays.asList(parent, child), parents);
	}

	@Test
	public void testPopulateNullCollectionWithNullCollection() {
		assertNull(CollectionUtils.populate(null, null));
	}

	@Test
	public void testPopulateNonNullCollectionWithNullCollection() {
		// Set up
		final Collection<Parent> collection = new ArrayList<Parent>();
		collection.add(new Parent());

		// Invoke
		final Collection<Parent> result = CollectionUtils.populate(collection,
		        null);

		// Check
		assertEquals(0, result.size());
	}

	@Test
	public void testPopulateNonNullCollectionWithNonNullCollection() {
		// Set up
		final Collection<Parent> originalCollection = new ArrayList<Parent>();
		originalCollection.add(new Parent());
		final Child child = new Child();

		// Invoke
		final Collection<Parent> result = CollectionUtils.populate(
		        originalCollection, Arrays.asList(child));

		// Check
		assertEquals(Collections.singletonList(child), result);
	}

	@Test
	public void testFirstElementOfNullCollection() {
		assertNull(CollectionUtils.firstElementOf(null));
	}

	@Test
	public void testFirstElementOfEmptyCollection() {
		assertNull(CollectionUtils.firstElementOf(Collections.emptySet()));
	}

	@Test
	public void testFirstElementOfSingleElementCollection() {
		final String member = "x";
		assertEquals(member,
		        CollectionUtils.firstElementOf(Collections.singleton(member)));
	}

	@Test
	public void testFirstElementOfMultiElementCollection() {
		final String[] members = { "x", "y", "z" };
		assertEquals(members[0],
		        CollectionUtils.firstElementOf(Arrays.asList(members)));
	}
}