String testString = "abcdefgh";
    CharSource source = newCharSource(testString);
    Reader joinedReader = CharSource.concat(source, source).openStream();

    String expectedString = testString + testString;
    assertEquals(expectedString, CharStreams.toString(joinedReader));
  }

  private static CharSource newCharSource(final String text) {
    return new CharSource() {
      @Override
      public Reader openStream() {

    String testString = "abcdefgh";
    CharSource source = newCharSource(testString);
    Reader joinedReader = CharSource.concat(source, source).openStream();

    String expectedString = testString + testString;
    assertEquals(expectedString, CharStreams.toString(joinedReader));
  }

  private static CharSource newCharSource(final String text) {
    return new CharSource() {
      @Override
      public Reader openStream() {

 * A generator of {@code TestSuite} instances for testing {@code CharSource} implementations.
 * Generates tests of all methods on a {@code CharSource} given various inputs the source is
 * expected to contain.
 *
 * @author Colin Decker
 */
@AndroidIncompatible // TODO(b/230620681): Make this available (even though we won't run it).
public class CharSourceTester extends SourceSinkTester<CharSource, String, CharSourceFactory> {

 * Utility methods and classes for I/O; for example input streams, output streams, readers, writers,
 * and files.
 *
 * <p>At the core of this package are the Source/Sink types: {@link ByteSource ByteSource}, {@link
 * CharSource CharSource}, {@link ByteSink ByteSink} and {@link CharSink CharSink}. They are
 * factories for I/O streams that provide many convenience methods that handle both opening and
 * closing streams for you.
 *

  /** Factory for {@link ByteSink} instances. */
  public interface ByteSinkFactory extends SinkFactory<ByteSink, byte[]> {}

  /** Factory for {@link CharSource} instances. */
  public interface CharSourceFactory extends SourceFactory<CharSource, String> {}

  /** Factory for {@link CharSink} instances. */
  public interface CharSinkFactory extends SinkFactory<CharSink, String> {}

 * A generator of {@code TestSuite} instances for testing {@code CharSource} implementations.
 * Generates tests of all methods on a {@code CharSource} given various inputs the source is
 * expected to contain.
 *
 * @author Colin Decker
 */
@AndroidIncompatible // TODO(b/230620681): Make this available (even though we won't run it).
public class CharSourceTester extends SourceSinkTester<CharSource, String, CharSourceFactory> {

 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
class MultiReader extends Reader {
  private final Iterator<? extends CharSource> it;
  @CheckForNull private Reader current;

  MultiReader(Iterator<? extends CharSource> readers) throws IOException {
    this.it = readers;
    advance();
  }

  /** Closes the current reader and opens the next one, if any. */

import java.io.InputStreamReader;
import java.io.Reader;

/**
 * A char source for testing that has configurable options.
 *
 * @author Colin Decker
 */
public class TestCharSource extends CharSource implements TestStreamSupplier {

  private final TestByteSource byteSource;

  public TestCharSource(String content, TestOption... options) {
    this.byteSource = new TestByteSource(content.getBytes(UTF_8), options);

  /** Factory for {@link ByteSink} instances. */
  public interface ByteSinkFactory extends SinkFactory<ByteSink, byte[]> {}

  /** Factory for {@link CharSource} instances. */
  public interface CharSourceFactory extends SourceFactory<CharSource, String> {}

  /** Factory for {@link CharSink} instances. */
  public interface CharSinkFactory extends SinkFactory<CharSink, String> {}

import java.io.InputStreamReader;
import java.io.Reader;

/**
 * A char source for testing that has configurable options.
 *
 * @author Colin Decker
 */
public class TestCharSource extends CharSource implements TestStreamSupplier {

  private final TestByteSource byteSource;

  public TestCharSource(String content, TestOption... options) {
    this.byteSource = new TestByteSource(content.getBytes(UTF_8), options);