@Test
    public void test_append_nullValue() {
        StringBuilder buf = new StringBuilder();
        Supplier<Object> supplier = () -> null;

        monitorTarget.append(buf, "testKey", supplier);
        assertEquals("\"testKey\":null", buf.toString());
    }

    // Test append method with Integer value
    @Test
    public void test_append_integerValue() {
        StringBuilder buf = new StringBuilder();

import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.collect.testing.features.MapFeature;
import java.util.Map.Entry;
import org.junit.Ignore;

/** Tester for {@code BiMap.entrySet} and methods on the entries in the set. */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")

import com.google.common.collect.testing.features.CollectionSize;
import com.google.common.collect.testing.features.MapFeature;
import java.util.Iterator;
import org.junit.Ignore;

/**
 * Tester for {@code BiMap.remove}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")

import java.util.List;
import java.util.Set;
import junit.framework.TestSuite;

/**
 * Concrete instantiation of {@link AbstractCollectionTestSuiteBuilder} for testing collections that
 * do not have a more specific tester like {@link ListTestSuiteBuilder} or {@link
 * SetTestSuiteBuilder}.
 *
 * @author Chris Povirk
 * @author Louis Wasserman
 */
@GwtIncompatible
public class CollectionTestSuiteBuilder<E>

  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNulls() {
    NullPointerTester tester = new NullPointerTester();

    tester.testAllPublicStaticMethods(InternetDomainName.class);
    tester.testAllPublicInstanceMethods(InternetDomainName.from("google.com"));
  }

        // Verify that the policyHandle passed to the constructor is the one used
        // This is implicitly tested by the object being constructed without errors.
        // If LsaPolicyHandle had methods called by the constructor, we would verify those calls.
    }

  public void testContainsKey() {
    boolean unused = create().containsKey(null);
  }

  public void testContainsValue() {
    boolean unused = create().containsValue(null);
  }

  public void testGet() {
    Object unused = create().get(null);
  }

  public void testPut() {
    create().put(null, null);
  }

  public void testPutAll() {
    create().putAll(new HashMap<String, Integer>());
  }

import java.util.Collection;
import java.util.List;
import org.jspecify.annotations.NullMarked;

/**
 * Creates collections containing unhashable sample elements, to be tested.
 *
 * @author Regina O'Dell
 */
@GwtCompatible
@NullMarked
public abstract class TestUnhashableCollectionGenerator<T extends Collection<UnhashableObject>>
    implements TestCollectionGenerator<UnhashableObject> {

          .buildOrThrow();

  public void testNulls() {
    NullPointerTester tester =
        new NullPointerTester().setDefault(String.class, "HmacMD5").setDefault(Key.class, MD5_KEY);
    tester.testAllPublicConstructors(MacHashFunction.class);
    tester.testAllPublicInstanceMethods(new MacHashFunction("HmacMD5", MD5_KEY, "toString"));
  }

  public void testHashing() throws Exception {

import java.util.Collection;
import java.util.List;
import java.util.Map.Entry;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;
import org.junit.Ignore;

/** Skeleton for a tester of a {@code BiMap}. */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.