* Interface for a supplier of streams that can report whether a stream was opened and whether that
 * stream was closed. Intended for use in a test where only a single stream should be opened and
 * possibly closed.
 *
 * @author Colin Decker
 */
@NullUnmarked
public interface TestStreamSupplier {

  /** Returns whether or not a new stream was opened. */
  boolean wasStreamOpened();

  /** Returns whether or not an open stream was closed. */

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import org.jspecify.annotations.NullUnmarked;

/**
 * A byte sink for testing that has configurable behavior.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class TestByteSink extends ByteSink implements TestStreamSupplier {

  private final ByteArrayOutputStream bytes = new ByteArrayOutputStream();

import java.io.IOException;
import java.io.InputStreamReader;
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) {

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import org.jspecify.annotations.NullUnmarked;

/**
 * A char sink for testing that has configurable behavior.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class TestCharSink extends CharSink implements TestStreamSupplier {

  private final TestByteSink byteSink;

  public TestCharSink(TestOption... options) {

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import org.jspecify.annotations.NullUnmarked;

/**
 * A char sink for testing that has configurable behavior.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class TestCharSink extends CharSink implements TestStreamSupplier {

  private final TestByteSink byteSink;

  public TestCharSink(TestOption... options) {

# Sub-dependencies { #sub-dependencies }

You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable" { #first-dependency-dependable }

You could create a first dependency ("dependable") like:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.Multimap;

/**
 * Helper methods/assertions for use with {@code com.google.common.collect} types.
 *
 * @author Colin Decker
 */
@GwtCompatible
final class GoogleHelpers {

  private GoogleHelpers() {}

  static void assertEmpty(Multimap<?, ?> multimap) {
    if (!multimap.isEmpty()) {

import com.google.common.annotations.J2ktIncompatible;

/**
 * Modes for opening a file for writing. The default when mode when none is specified is to truncate
 * the file before writing.
 *
 * @author Colin Decker
 */
@J2ktIncompatible
@GwtIncompatible
public enum FileWriteMode {
  /** Specifies that writes to the opened file should append to the end of the file. */
  APPEND

import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests for {@link AbstractListeningExecutorService}.
 *
 * @author Colin Decker
 */
@NullUnmarked
@GwtIncompatible
@J2ktIncompatible
public class AbstractListeningExecutorServiceTest extends TestCase {

  public void testSubmit() throws Exception {
    /*

import java.util.zip.Checksum;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests for ChecksumHashFunction.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class ChecksumHashFunctionTest extends TestCase {

  public void testCrc32_equalsChecksumValue() throws Exception {
    assertChecksum(CRC_32, "");
    assertChecksum(CRC_32, "Z");