CollectionUtilsTest.java

package org.springframework.roo.support.util;

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

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

import org.apache.commons.lang3.StringUtils;
import org.junit.Test;

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

  private static class Child extends Parent {
  }

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

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

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

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

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

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

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

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