import java.util.List;
import junit.framework.TestCase;

/**
 * @param <S> the source or sink type
 * @param <T> the data type (byte[] or String)
 * @param <F> the factory type
 * @author Colin Decker
 */
@AndroidIncompatible // TODO(b/230620681): Make this available (even though we won't run it).
public class SourceSinkTester<S, T, F extends SourceSinkFactory<S, T>> extends TestCase {

  static final String LOREM_IPSUM =

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterators;
import java.util.Iterator;
import junit.framework.TestCase;

/**
 * Tests for {@link SubscriberRegistry}.
 *
 * @author Colin Decker
 */
public class SubscriberRegistryTest extends TestCase {

  private final SubscriberRegistry registry = new SubscriberRegistry(new EventBus());

  public void testRegister() {

import javax.annotation.CheckForNull;

/**
 * A {@link Reader} that reads the characters in a {@link CharSequence}. Like {@code StringReader},
 * but works with any {@link CharSequence}.
 *
 * @author Colin Decker
 */
// TODO(cgdecker): make this public? as a type, or a method in CharStreams?
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class CharSequenceReader extends Reader {

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import junit.framework.TestCase;

/**
 * Tests for {@link Dispatcher} implementations.
 *
 * @author Colin Decker
 */
public class DispatcherTest extends TestCase {

  private final EventBus bus = new EventBus();

  private final IntegerSubscriber i1 = new IntegerSubscriber("i1");

import javax.annotation.CheckForNull;

/**
 * A {@link Reader} that reads the characters in a {@link CharSequence}. Like {@code StringReader},
 * but works with any {@link CharSequence}.
 *
 * @author Colin Decker
 */
// TODO(cgdecker): make this public? as a type, or a method in CharStreams?
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class CharSequenceReader extends Reader {

import static org.junit.Assert.assertThrows;

import java.io.IOException;
import java.nio.CharBuffer;
import junit.framework.TestCase;

/**
 * Tests for {@link CharSequenceReader}.
 *
 * @author Colin Decker
 */
public class CharSequenceReaderTest extends TestCase {

  public void testReadEmptyString() throws IOException {
    assertReadsCorrectly("");
  }

# Classes as Dependencies

Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example

In the previous example, we were returning a `dict` from our dependency ("dependable"):

//// tab | Python 3.10+

```Python hl_lines="9"
{!> ../../docs_src/dependencies/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="11"

 * 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> {

import java.util.logging.Logger;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Base test case class for I/O tests.
 *
 * @author Chris Nokleberg
 * @author Colin Decker
 */
public abstract class IoTestCase extends TestCase {

  private static final Logger logger = Logger.getLogger(IoTestCase.class.getName());

  static final String I18N =

 * Closeable}. A {@link java.io.Reader} implements both of those interfaces. Similarly for {@code
 * Appendable & Closeable} and {@link java.io.Writer}.
 *
 * @author Chris Nokleberg
 * @author Bin Zhu
 * @author Colin Decker
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class CharStreams {

  // 2K chars (4K bytes)
  private static final int DEFAULT_BUF_SIZE = 0x800;