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(String text) {
    return new CharSource() {
      @Override
      public Reader openStream() {

 * 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).
@NullUnmarked
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.
 *

 *
 * @author Bin Zhu
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
final class MultiReader extends Reader {
  private final Iterator<? extends CharSource> it;
  private @Nullable Reader current;

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

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

    @Override
    public String toString() {
      return "Resources.asByteSource(" + url + ")";
    }
  }

  /**
   * Returns a {@link CharSource} that reads from the given URL using the given character set.
   *
   * @since 14.0
   */
  public static CharSource asCharSource(URL url, Charset charset) {
    return asByteSource(url).asCharSource(charset);
  }

  /**
   * Reads all bytes from a URL into a byte array.

import java.io.Reader;
import org.jspecify.annotations.NullUnmarked;

/**
 * A char source for testing that has configurable options.
 *
 * @author Colin Decker
 */
@NullUnmarked
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);

  @Override
  public String getName() {
    return super.getName() + " [" + suiteName + " [" + caseDesc + "]]";
  }

  protected static ImmutableList<String> getLines(String string) {
    try {
      return new CharSource() {
        @Override
        public Reader openStream() throws IOException {
          return new StringReader(string);
        }
      }.readLines();
    } catch (IOException e) {