assertThat(Optional.of("a").or(Suppliers.ofInstance("fallback"))).isEqualTo("a");
  }

  public void testOr_supplier_absent() {
    assertEquals("fallback", Optional.absent().or(Suppliers.ofInstance("fallback")));
  }

  public void testOr_nullSupplier_absent() {
    Supplier<Object> nullSupplier = (Supplier<Object>) Suppliers.<@Nullable Object>ofInstance(null);
    Optional<Object> absentOptional = Optional.absent();

   * supplier that is serializable, use {@code (Supplier<T> & Serializable) () -> instance}.
   */
  public static <T extends @Nullable Object> Supplier<T> ofInstance(
      @ParametricNullness T instance) {
    return new SupplierOfInstance<>(instance);
  }

  private static final class SupplierOfInstance<T extends @Nullable Object>
      implements Supplier<T>, Serializable {

   * supplier that is serializable, use {@code (Supplier<T> & Serializable) () -> instance}.
   */
  public static <T extends @Nullable Object> Supplier<T> ofInstance(
      @ParametricNullness T instance) {
    return new SupplierOfInstance<>(instance);
  }

  private static final class SupplierOfInstance<T extends @Nullable Object>
      implements Supplier<T>, Serializable {

  }

  @J2ktIncompatible
  @GwtIncompatible // threads
  public void testRenaming() throws Exception {
    String oldName = Thread.currentThread().getName();
    Supplier<String> newName = Suppliers.ofInstance("MyCrazyThreadName");
    Callable<@Nullable Void> callable =
        () -> {
          assertThat(Thread.currentThread().getName()).isEqualTo(newName.get());
          return null;
        };

  }

  @J2ktIncompatible
  @GwtIncompatible // threads
  public void testRenaming() throws Exception {
    String oldName = Thread.currentThread().getName();
    Supplier<String> newName = Suppliers.ofInstance("MyCrazyThreadName");
    Callable<@Nullable Void> callable =
        () -> {
          assertThat(Thread.currentThread().getName()).isEqualTo(newName.get());
          return null;
        };

  }

  @SuppressWarnings("ReturnValueIgnored")
  public void testMaximumWeight_withoutWeigher() {
    CacheBuilder<Object, Object> builder = CacheBuilder.from(parse("maximumWeight=9000"));
    assertThrows(
        IllegalStateException.class,
        () -> builder.build(CacheLoader.from(Suppliers.ofInstance(null))));
  }

    new EqualsTester()
        .addEqualityGroup(function, Functions.forSupplier(supplier))
        .addEqualityGroup(Functions.forSupplier(new CountingSupplier()))
        .addEqualityGroup(Functions.forSupplier(Suppliers.ofInstance(12)))
        .addEqualityGroup(Functions.toStringFunction())
        .testEquals();
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testForSupplierSerializable() {

  }

  public void testThreadRenaming() {
    Executor renamingExecutor =
        renamingDecorator(newDirectExecutorService(), Suppliers.ofInstance("FooBar"));
    String oldName = Thread.currentThread().getName();
    renamingExecutor.execute(
        () -> assertThat(Thread.currentThread().getName()).isEqualTo("FooBar"));

  }

  public void testThreadRenaming() {
    Executor renamingExecutor =
        renamingDecorator(newDirectExecutorService(), Suppliers.ofInstance("FooBar"));
    String oldName = Thread.currentThread().getName();
    renamingExecutor.execute(
        () -> assertThat(Thread.currentThread().getName()).isEqualTo("FooBar"));

    new EqualsTester()
        .addEqualityGroup(function, Functions.forSupplier(supplier))
        .addEqualityGroup(Functions.forSupplier(new CountingSupplier()))
        .addEqualityGroup(Functions.forSupplier(Suppliers.ofInstance(12)))
        .addEqualityGroup(Functions.toStringFunction())
        .testEquals();
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testForSupplierSerializable() {