return "";
              }
            };
          }
        },
        "toString()");
  }

  public void testFailsToForwardHashCode() {
    tester.includingEquals();
    assertFailure(
        Runnable.class,
        new Function<Runnable, Runnable>() {
          @Override
          public Runnable apply(final Runnable runnable) {

  /**
   * Asks for {@link Object#equals} and {@link Object#hashCode} to be tested. That is, forwarding
   * wrappers of equal instances should be equal.
   */
  @CanIgnoreReturnValue
  public ForwardingWrapperTester includingEquals() {
    this.testsEquals = true;
    return this;
  }

  /**
   * Tests that the forwarding wrapper returned by {@code wrapperFunction} properly forwards method

  /**
   * Asks for {@link Object#equals} and {@link Object#hashCode} to be tested. That is, forwarding
   * wrappers of equal instances should be equal.
   */
  @CanIgnoreReturnValue
  public ForwardingWrapperTester includingEquals() {
    this.testsEquals = true;
    return this;
  }

  /**
   * Tests that the forwarding wrapper returned by {@code wrapperFunction} properly forwards method