guava/guava-tests/test/com/google/common/base/ConverterTest.java

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.base;

import static com.google.common.base.Functions.toStringFunction;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.primitives.Longs;
import com.google.common.testing.EqualsTester;
import com.google.common.testing.SerializableTester;

import junit.framework.TestCase;

import java.util.Iterator;
import java.util.List;

/**
 * Unit tests for {@link Converter}.
 */
@GwtCompatible
public class ConverterTest extends TestCase {

  private static final Converter<String, Long> STR_TO_LONG =
      new Converter<String, Long>() {
        @Override public Long doForward(String object) {
          return Long.valueOf(object);
        }

        @Override public String doBackward(Long object) {
          return String.valueOf(object);
        }

        @Override public String toString() {
          return "string2long";
        }
      };

  private static final Long LONG_VAL = 12345L;
  private static final String STR_VAL = "12345";

  private static final ImmutableList<String> STRINGS = ImmutableList.of("123", "456");
  private static final ImmutableList<Long> LONGS = ImmutableList.of(123L, 456L);

  public void testConverter() {
    assertEquals(LONG_VAL, STR_TO_LONG.convert(STR_VAL));
    assertEquals(STR_VAL, STR_TO_LONG.reverse().convert(LONG_VAL));

    Iterable<Long> convertedValues = STR_TO_LONG.convertAll(STRINGS);
    assertEquals(LONGS, ImmutableList.copyOf(convertedValues));
  }

  public void testConvertAllIsView() {
    List<String> mutableList = Lists.newArrayList("789", "123");
    Iterable<Long> convertedValues = STR_TO_LONG.convertAll(mutableList);
    assertEquals(ImmutableList.of(789L, 123L), ImmutableList.copyOf(convertedValues));

    Iterator<Long> iterator = convertedValues.iterator();
    iterator.next();
    iterator.remove();
    assertEquals(ImmutableList.of("123"), mutableList);
  }

  public void testReverse() {
    Converter<Long, String> reverseConverter = STR_TO_LONG.reverse();

    assertEquals(STR_VAL, reverseConverter.convert(LONG_VAL));
    assertEquals(LONG_VAL, reverseConverter.reverse().convert(STR_VAL));

    Iterable<String> convertedValues = reverseConverter.convertAll(LONGS);
    assertEquals(STRINGS, ImmutableList.copyOf(convertedValues));

    assertSame(STR_TO_LONG, reverseConverter.reverse());

    assertEquals("string2long.reverse()", reverseConverter.toString());

    new EqualsTester()
        .addEqualityGroup(STR_TO_LONG, STR_TO_LONG.reverse().reverse())
        .addEqualityGroup(STR_TO_LONG.reverse(), STR_TO_LONG.reverse())
        .testEquals();
  }

  public void testReverseReverse() {
    Converter<String, Long> converter = STR_TO_LONG;
    assertEquals(converter, converter.reverse().reverse());
  }

  public void testApply() {
    assertEquals(LONG_VAL, STR_TO_LONG.apply(STR_VAL));
  }

  private static class StringWrapper {
    private final String value;

    public StringWrapper(String value) {
      this.value = value;
    }
  }

  public void testAndThen() {
    Converter<StringWrapper, String> first = new Converter<StringWrapper, String>() {
      @Override public String doForward(StringWrapper object) {
        return object.value;
      }

      @Override public StringWrapper doBackward(String object) {
        return new StringWrapper(object);
      }

      @Override public String toString() {
        return "StringWrapper";
      }
    };

    Converter<StringWrapper, Long> converter = first.andThen(STR_TO_LONG);

    assertEquals(LONG_VAL, converter.convert(new StringWrapper(STR_VAL)));
    assertEquals(STR_VAL, converter.reverse().convert(LONG_VAL).value);

    assertEquals("StringWrapper.andThen(string2long)", converter.toString());

    assertEquals(first.andThen(STR_TO_LONG), first.andThen(STR_TO_LONG));
  }

  public void testIdentityConverter() {
    Converter<String, String> stringIdentityConverter = Converter.identity();

    assertSame(stringIdentityConverter, stringIdentityConverter.reverse());
    assertSame(STR_TO_LONG, stringIdentityConverter.andThen(STR_TO_LONG));

    assertSame(STR_VAL, stringIdentityConverter.convert(STR_VAL));
    assertSame(STR_VAL, stringIdentityConverter.reverse().convert(STR_VAL));

    assertEquals("Converter.identity()", stringIdentityConverter.toString());

    assertSame(Converter.identity(), Converter.identity());
  }

  public void testFrom() {
    Function<String, Integer> forward = new Function<String, Integer>() {
      @Override public Integer apply(String input) {
        return Integer.parseInt(input);
      }
    };
    Function<Object, String> backward = toStringFunction();

    Converter<String, Number> converter = Converter.<String, Number>from(forward, backward);

    assertNull(converter.convert(null));
    assertNull(converter.reverse().convert(null));

    assertEquals((Integer) 5, converter.convert("5"));
    assertEquals("5", converter.reverse().convert(5));
  }

  public void testNullIsPassedThrough() {
    Converter<String, String> nullsArePassed = sillyConverter(false);
    assertEquals("forward", nullsArePassed.convert("foo"));
    assertEquals("forward", nullsArePassed.convert(null));
    assertEquals("backward", nullsArePassed.reverse().convert("foo"));
    assertEquals("backward", nullsArePassed.reverse().convert(null));
  }

  public void testNullIsNotPassedThrough() {
    Converter<String, String> nullsAreHandled = sillyConverter(true);
    assertEquals("forward", nullsAreHandled.convert("foo"));
    assertEquals(null, nullsAreHandled.convert(null));
    assertEquals("backward", nullsAreHandled.reverse().convert("foo"));
    assertEquals(null, nullsAreHandled.reverse().convert(null));
  }

  private static Converter<String, String> sillyConverter(final boolean handleNullAutomatically) {
    return new Converter<String, String>(handleNullAutomatically) {
      @Override public String doForward(String string) {
        return "forward";
      }
      @Override public String doBackward(String string) {
        return "backward";
      }
    };
  }

  public void testSerialization_identity() {
    Converter<String, String> identityConverter = Converter.identity();
    SerializableTester.reserializeAndAssert(identityConverter);
  }

  public void testSerialization_reverse() {
    Converter<Long, String> reverseConverter = Longs.stringConverter().reverse();
    SerializableTester.reserializeAndAssert(reverseConverter);
  }

  public void testSerialization_andThen() {
    Converter<String, Long> converterA = Longs.stringConverter();
    Converter<Long, String> reverseConverter = Longs.stringConverter().reverse();
    Converter<String, String> composedConverter = converterA.andThen(reverseConverter);
    SerializableTester.reserializeAndAssert(composedConverter);
  }

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