* 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
 */
public interface TestStreamSupplier {

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

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

 * 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
 */
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.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;

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

  public void testSubmit() throws Exception {
    /*
     * Mostly just tests that TrustedListenableFutureTask are created and run; tests for

import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;
import junit.framework.TestCase;

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

  public void testSubmit() throws Exception {
    /*
     * Mostly just tests that TrustedListenableFutureTask are created and run; tests for

import java.io.IOException;
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) {

## Use the instance as a dependency

Then, we could use this `checker` in a `Depends(checker)`, instead of `Depends(FixedContentQueryChecker)`, because the dependency is the instance, `checker`, not the class itself.

And when solving the dependency, **FastAPI** will call this `checker` like:

```Python
checker(q="somequery")
```

import com.google.common.collect.ImmutableSet;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

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

  private final ByteArrayOutputStream bytes = new ByteArrayOutputStream();
  private final ImmutableSet<TestOption> options;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.FilterWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;

/** @author Colin Decker */
public class TestWriter extends FilterWriter {

  private final TestOutputStream out;

  public TestWriter(TestOption... options) throws IOException {

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 java.io.FilterWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;

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

  private final TestByteSink byteSink;

  public TestCharSink(TestOption... options) {