checkCanReserializeSingleton(Functions.identity());
  }

  public void testToStringFunction_apply() {
    assertEquals("3", Functions.toStringFunction().apply(3));
    assertEquals("hiya", Functions.toStringFunction().apply("hiya"));
    assertEquals(
        "I'm a string",
        Functions.toStringFunction()
            .apply(
                new Object() {
                  @Override
                  public String toString() {

    EquivalenceTester.of(Equivalence.equals().onResultOf(Functions.toStringFunction()))
        .addEquivalenceGroup(new IntValue(1), new IntValue(1))
        .addEquivalenceGroup(new IntValue(2))
        .test();
  }

  public void testOnResultOf_equals() {
    new EqualsTester()
        .addEqualityGroup(
            Equivalence.identity().onResultOf(Functions.toStringFunction()),

    EquivalenceTester.of(Equivalence.equals().onResultOf(Functions.toStringFunction()))
        .addEquivalenceGroup(new IntValue(1), new IntValue(1))
        .addEquivalenceGroup(new IntValue(2))
        .test();
  }

  public void testOnResultOf_equals() {
    new EqualsTester()
        .addEqualityGroup(
            Equivalence.identity().onResultOf(Functions.toStringFunction()),

  }

  @Override
  protected Map<String, String> makePopulatedMap() {
    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(
        new UnmodifiableIteratorMap<String, Integer>(underlying), Functions.toStringFunction());
  }

  @Override

    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(underlying, Functions.toStringFunction());
  }

    checkCanReserializeSingleton(Functions.identity());
  }

  public void testToStringFunction_apply() {
    assertEquals("3", Functions.toStringFunction().apply(3));
    assertEquals("hiya", Functions.toStringFunction().apply("hiya"));
    assertEquals(
        "I'm a string",
        Functions.toStringFunction()
            .apply(
                new Object() {
                  @Override
                  public String toString() {

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Functions.toStringFunction;
import static com.google.common.collect.Maps.uniqueIndex;
import static java.util.Arrays.asList;

import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;

    SerializableTester.reserializeAndAssert(composedConverter);
  }

  public void testSerialization_from() {
    Converter<String, String> dumb = Converter.from(toStringFunction(), toStringFunction());
    SerializableTester.reserializeAndAssert(dumb);
  }

   * the JDK {@link java.util.function.Function} class, see {@link Function}.
   */
  public static Function<Object, String> toStringFunction() {
    return ToStringFunction.INSTANCE;
  }

  // enum singleton pattern
  private enum ToStringFunction implements Function<Object, String> {
    INSTANCE;

    @Override
    public String apply(Object o) {
      checkNotNull(o); // eager for GWT.

    Map<String, Integer> underlying = new HashMap<>();
    underlying.put("a", 1);
    underlying.put("b", 2);
    underlying.put("c", 3);
    return transformValues(underlying, Functions.toStringFunction());
  }