LazyStringArrayListTest.java

// Protocol Buffers - Google's data interchange format
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package com.google.protobuf;

import static java.util.Arrays.asList;

import java.util.ArrayList;
import java.util.Collections;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import junit.framework.TestCase;

/**
 * Tests for {@link LazyStringArrayList}.
 *
 * @author jonp@google.com (Jon Perlow)
 */
public class LazyStringArrayListTest extends TestCase {

  private static String STRING_A = "A";
  private static String STRING_B = "B";
  private static String STRING_C = "C";

  private static ByteString BYTE_STRING_A = ByteString.copyFromUtf8("A");
  private static ByteString BYTE_STRING_B = ByteString.copyFromUtf8("B");
  private static ByteString BYTE_STRING_C = ByteString.copyFromUtf8("C");

  public void testJustStrings() {
    LazyStringArrayList list = new LazyStringArrayList();
    list.add(STRING_A);
    list.add(STRING_B);
    list.add(STRING_C);

    assertEquals(3, list.size());
    assertSame(STRING_A, list.get(0));
    assertSame(STRING_B, list.get(1));
    assertSame(STRING_C, list.get(2));

    list.set(1, STRING_C);
    assertSame(STRING_C, list.get(1));

    list.remove(1);
    assertSame(STRING_A, list.get(0));
    assertSame(STRING_C, list.get(1));

    List<ByteString> byteStringList = list.asByteStringList();
    assertEquals(BYTE_STRING_A, byteStringList.get(0));
    assertEquals(BYTE_STRING_C, byteStringList.get(1));

    // Underlying list should be transformed.
    assertSame(byteStringList.get(0), list.getByteString(0));
    assertSame(byteStringList.get(1), list.getByteString(1));
  }

  public void testJustByteString() {
    LazyStringArrayList list = new LazyStringArrayList();
    list.add(BYTE_STRING_A);
    list.add(BYTE_STRING_B);
    list.add(BYTE_STRING_C);

    assertEquals(3, list.size());
    assertSame(BYTE_STRING_A, list.getByteString(0));
    assertSame(BYTE_STRING_B, list.getByteString(1));
    assertSame(BYTE_STRING_C, list.getByteString(2));

    list.remove(1);
    assertSame(BYTE_STRING_A, list.getByteString(0));
    assertSame(BYTE_STRING_C, list.getByteString(1));

    List<ByteString> byteStringList = list.asByteStringList();
    assertSame(BYTE_STRING_A, byteStringList.get(0));
    assertSame(BYTE_STRING_C, byteStringList.get(1));
  }

  public void testConversionBackAndForth() {
    LazyStringArrayList list = new LazyStringArrayList();
    list.add(STRING_A);
    list.add(BYTE_STRING_B);
    list.add(BYTE_STRING_C);

    // String a should be the same because it was originally a string
    assertSame(STRING_A, list.get(0));

    // String b and c should be different because the string has to be computed
    // from the ByteString
    String bPrime = list.get(1);
    assertNotSame(STRING_B, bPrime);
    assertEquals(STRING_B, bPrime);
    String cPrime = list.get(2);
    assertNotSame(STRING_C, cPrime);
    assertEquals(STRING_C, cPrime);

    // String c and c should stay the same once cached.
    assertSame(bPrime, list.get(1));
    assertSame(cPrime, list.get(2));

    // ByteString needs to be computed from string for both a and b
    ByteString aPrimeByteString = list.getByteString(0);
    assertEquals(BYTE_STRING_A, aPrimeByteString);
    ByteString bPrimeByteString = list.getByteString(1);
    assertNotSame(BYTE_STRING_B, bPrimeByteString);
    assertEquals(BYTE_STRING_B, list.getByteString(1));

    // Once cached, ByteString should stay cached.
    assertSame(aPrimeByteString, list.getByteString(0));
    assertSame(bPrimeByteString, list.getByteString(1));
  }

  public void testCopyConstructorCopiesByReference() {
    LazyStringArrayList list1 = new LazyStringArrayList();
    list1.add(STRING_A);
    list1.add(BYTE_STRING_B);
    list1.add(BYTE_STRING_C);

    LazyStringArrayList list2 = new LazyStringArrayList(list1);
    assertEquals(3, list2.size());
    assertSame(STRING_A, list2.get(0));
    assertSame(BYTE_STRING_B, list2.getByteString(1));
    assertSame(BYTE_STRING_C, list2.getByteString(2));
  }

  public void testListCopyConstructor() {
    List<String> list1 = new ArrayList<String>();
    list1.add(STRING_A);
    list1.add(STRING_B);
    list1.add(STRING_C);

    LazyStringArrayList list2 = new LazyStringArrayList(list1);
    assertEquals(3, list2.size());
    assertSame(STRING_A, list2.get(0));
    assertSame(STRING_B, list2.get(1));
    assertSame(STRING_C, list2.get(2));
  }

  public void testAddAllCopiesByReferenceIfPossible() {
    LazyStringArrayList list1 = new LazyStringArrayList();
    list1.add(STRING_A);
    list1.add(BYTE_STRING_B);
    list1.add(BYTE_STRING_C);

    LazyStringArrayList list2 = new LazyStringArrayList();
    list2.addAll(list1);

    assertEquals(3, list2.size());
    assertSame(STRING_A, list2.get(0));
    assertSame(BYTE_STRING_B, list2.getByteString(1));
    assertSame(BYTE_STRING_C, list2.getByteString(2));
  }
  
  public void testModificationWithIteration() {
    LazyStringArrayList list = new LazyStringArrayList();
    list.addAll(asList(STRING_A, STRING_B, STRING_C));
    Iterator<String> iterator = list.iterator();
    assertEquals(3, list.size());
    assertEquals(STRING_A, list.get(0));
    assertEquals(STRING_A, iterator.next());
    
    // Does not structurally modify.
    iterator = list.iterator();
    list.set(0, STRING_B);
    iterator.next();
    
    list.remove(0);
    try {
      iterator.next();
      fail();
    } catch (ConcurrentModificationException e) {
      // expected
    }
    
    iterator = list.iterator();
    list.add(0, STRING_C);
    try {
      iterator.next();
      fail();
    } catch (ConcurrentModificationException e) {
      // expected
    }
  }
  
  public void testMakeImmutable() {
    LazyStringArrayList list = new LazyStringArrayList();
    list.add(STRING_A);
    list.add(STRING_B);
    list.add(STRING_C);
    list.makeImmutable();
    assertGenericListImmutable(list, STRING_A);
    
    // LazyStringArrayList has extra methods not covered in the generic
    // assertion.
    
    try {
      list.add(BYTE_STRING_A.toByteArray());
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.add(BYTE_STRING_A);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.addAllByteArray(Collections.singletonList(BYTE_STRING_A.toByteArray()));
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.addAllByteString(asList(BYTE_STRING_A));
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.mergeFrom(new LazyStringArrayList());
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.set(0, BYTE_STRING_A.toByteArray());
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.set(0, BYTE_STRING_A);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
  }
  
  public void testImmutabilityPropagation() {
    LazyStringArrayList list = new LazyStringArrayList();
    list.add(STRING_A);
    list.makeImmutable();

    assertGenericListImmutable(list.asByteStringList(), BYTE_STRING_A);
    
    // Arrays use reference equality so need to retrieve the underlying value
    // to properly test deep immutability.
    List<byte[]> byteArrayList = list.asByteArrayList();
    assertGenericListImmutable(byteArrayList, byteArrayList.get(0));
  }
  
  @SuppressWarnings("unchecked")
  private static <T> void assertGenericListImmutable(List<T> list, T value) {
    try {
      list.add(value);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.add(0, value);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.addAll(asList(value));
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.addAll(0, asList(value));
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }

    try {
      list.clear();
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.remove(0);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.remove(value);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.removeAll(asList(value));
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.retainAll(asList());
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.retainAll(asList());
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
    
    try {
      list.set(0, value);
      fail();
    } catch (UnsupportedOperationException e) {
      // expected
    }
  }
}