Escaper escaper = Escapers.nullEscaper();
    EscaperAsserts.assertBasic(escaper);
    String s = "\0\n\t\\az09~\uD800\uDC00\uFFFF";
    assertWithMessage("null escaper should have no effect").that(escaper.escape(s)).isEqualTo(s);
  }

  public void testBuilderInitialStateNoReplacement() {
    // Unsafe characters aren't modified by default (unsafeReplacement == null).

/**
 * Superclass for all {@code Multimap} testers.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
@NullMarked
public abstract class AbstractMultimapTester<

 *
 * @author Chris Povirk
 * @author Kevin Bourrillion
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
@NullMarked
public class MapPutAllTester<K extends @Nullable Object, V extends @Nullable Object>

 *
 * @author Chris Povirk
 * @author Kevin Bourrillion
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class MapCreationTester<K, V> extends AbstractMapTester<K, V> {
  @MapFeature.Require(ALLOWS_NULL_KEYS)

import org.junit.Ignore;

/** Tester for {@code BiMap.put} and {@code BiMap.forcePut}. */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class BiMapPutTester<K, V> extends AbstractBiMapTester<K, V> {

  @MapFeature.Require(SUPPORTS_PUT)

 *
 * @author George van den Driessche
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class CollectionRemoveTester<E> extends AbstractCollectionTester<E> {

/**
 * Tester for {@code Multimap.entries}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class MultimapEntriesTester<K, V> extends AbstractMultimapTester<K, V, Multimap<K, V>> {

/**
 * Tests for {@link Multimap#replaceValues(Object, Iterable)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class MultimapReplaceValuesTester<K, V>
    extends AbstractMultimapTester<K, V, Multimap<K, V>> {

 *
 * @author Chris Povirk
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class ListAddAtIndexTester<E> extends AbstractListTester<E> {

 *
 * @author George van den Driessche
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class ListSetTester<E> extends AbstractListTester<E> {
  @ListFeature.Require(SUPPORTS_SET)