Faster, indexed, heuristic doubly-linked list data structure in Java: unit tests

Question

Here I have the unit tests for the indexed doubly-linked list.

It goes like this:

package com.github.coderodde.util;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Random;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.stream.Collectors;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;
import org.junit.Before;
import org.junit.Test;
public class LinkedListTest {
 private final LinkedList<Integer> list = new LinkedList<>();
 @Before
 public void setUp() {
 list.clear();
 }
 @Test
 public void testAdd() {
 assertTrue(list.isEmpty());
 assertEquals(0, list.size());
 list.add(1);
 assertEquals(1, list.size());
 assertFalse(list.isEmpty());
 assertEquals(Integer.valueOf(1), list.get(0));
 list.add(2);
 assertEquals(2, list.size());
 assertFalse(list.isEmpty());
 assertEquals(Integer.valueOf(1), list.get(0));
 assertEquals(Integer.valueOf(2), list.get(1));
 }
 @Test
 public void testAddFirst() {
 assertTrue(list.isEmpty());
 assertEquals(0, list.size());
 list.addFirst(1);
 assertEquals(1, list.size());
 assertFalse(list.isEmpty());
 assertEquals(Integer.valueOf(1), list.get(0));
 list.addFirst(2);
 assertEquals(2, list.size());
 assertFalse(list.isEmpty());
 assertEquals(Integer.valueOf(2), list.get(0));
 assertEquals(Integer.valueOf(1), list.get(1));
 }
 @Test(expected = IndexOutOfBoundsException.class)
 public void testThrowsOnAccessingEmptyList() {
 list.get(0);
 }
 @Test(expected = IndexOutOfBoundsException.class) 
 public void testOnNegativeIndexInEmptyList() {
 list.get(-1);
 }
 @Test(expected = IndexOutOfBoundsException.class) 
 public void testOnNegativeIndexInNonEmptyList() {
 list.addFirst(10);
 list.get(-1);
 }
 @Test(expected = IndexOutOfBoundsException.class) 
 public void testOnTooLargeIndex() {
 list.addFirst(10);
 list.addLast(20);
 list.get(2);
 }
 @Test
 public void testAddIndexAndElement() {
 list.add(0, 1);
 assertEquals(Integer.valueOf(1), list.get(0));
 list.add(0, 2);
 assertEquals(Integer.valueOf(2), list.get(0));
 assertEquals(Integer.valueOf(1), list.get(1));
 list.add(2, 10);
 assertEquals(Integer.valueOf(2), list.get(0));
 assertEquals(Integer.valueOf(1), list.get(1));
 assertEquals(Integer.valueOf(10), list.get(2));
 list.add(2, 100);
 assertEquals(Integer.valueOf(2), list.get(0));
 assertEquals(Integer.valueOf(1), list.get(1));
 assertEquals(Integer.valueOf(100), list.get(2));
 assertEquals(Integer.valueOf(10), list.get(3));
 }
 @Test
 public void testAddCollectionOneElementToEmptyList() {
 List<Integer> c = new ArrayList<>();
 c.add(100);
 list.addAll(c);
 assertFalse(list.isEmpty());
 assertEquals(1, list.size());
 assertEquals(Integer.valueOf(100), list.get(0));
 }
 @Test
 public void testAddCollectionThreeElementsToEmptyList() {
 assertTrue(list.isEmpty());
 assertEquals(0, list.size());
 List<Integer> c = Arrays.asList(1, 2, 3);
 list.addAll(c);
 assertFalse(list.isEmpty());
 assertEquals(3, list.size());
 for (int i = 0; i < list.size(); i++) {
 assertEquals(Integer.valueOf(i + 1), list.get(i));
 }
 }
 @Test
 public void testAddCollectionAtIndex() {
 list.addAll(0, Arrays.asList(2, 3)); // setAll
 list.addAll(0, Arrays.asList(0, 1)); // prependAll
 list.addAll(4, Arrays.asList(6, 7)); // appendAll
 list.addAll(4, Arrays.asList(4, 5)); // insertAll
 for (int i = 0; i < list.size(); i++) {
 assertEquals(Integer.valueOf(i), list.get(i));
 }
 }
 @Test
 public void testRemoveInt() {
 list.addAll(Arrays.asList(0, 1, 2, 3, 4));
 assertEquals(Integer.valueOf(0), list.remove(0));
 assertEquals(Integer.valueOf(4), list.remove(3));
 assertEquals(Integer.valueOf(2), list.remove(1));
 assertEquals(Integer.valueOf(1), list.remove(0));
 assertEquals(Integer.valueOf(3), list.remove(0));
 }
 @Test
 public void testBasicIteratorUsage() {
 for (int i = 0; i < 1000; i++) {
 list.add(i);
 }
 Iterator<Integer> iterator = list.iterator();
 for (int i = 0; i < 1000; i++) {
 assertTrue(iterator.hasNext());
 assertEquals(Integer.valueOf(i), iterator.next());
 }
 assertFalse(iterator.hasNext());
 }
 @Test
 public void bruteForceAddCollectionAtIndex() {
 long seed = System.currentTimeMillis();
 System.out.println("- bruteForceAddCollectionAtIndex.seed = " + seed);
 Random random = new Random(seed);
 list.addAll(getIntegerList());
 java.util.LinkedList<Integer> referenceList = 
 new java.util.LinkedList<>(list);
 for (int op = 0; op < 100; op++) {
 int index = random.nextInt(list.size());
 Collection<Integer> coll = getIntegerList(random.nextInt(40));
 referenceList.addAll(index, coll);
 list.addAll(index, coll);
 if (!listsEqual(list, referenceList)) {
 fail("Lists not equal!");
 }
 }
 }
 @Test
 public void removeAtIndex() {
 list.addAll(Arrays.asList(0, 1, 2, 3, 4));
 assertEquals(Integer.valueOf(2), list.remove(2));
 assertEquals(Integer.valueOf(0), list.remove(0));
 assertEquals(Integer.valueOf(4), list.remove(2));
 }
 @Test
 public void removeObject() {
 list.addAll(Arrays.asList(0, 1, 2, 3, 4));
 assertFalse(list.remove(Integer.valueOf(10)));
 assertFalse(list.remove(null));
 list.add(3, null);
 assertTrue(list.remove(null));
 assertTrue(list.remove(Integer.valueOf(4)));
 assertTrue(list.remove(Integer.valueOf(0)));
 assertTrue(list.remove(Integer.valueOf(2)));
 assertFalse(list.remove(Integer.valueOf(2)));
 }
 @Test
 public void basicIteratorTraversal() {
 list.addAll(Arrays.asList(0, 1, 2, 3, 4));
 Iterator<Integer> iter = list.iterator();
 for (int i = 0; i < list.size(); i++) {
 assertTrue(iter.hasNext());
 assertEquals(Integer.valueOf(i), iter.next());
 }
 iter = list.iterator();
 class MyConsumer implements Consumer<Integer> {
 int total;
 @Override
 public void accept(Integer t) {
 total += t;
 }
 }
 MyConsumer myConsumer = new MyConsumer();
 list.iterator().forEachRemaining(myConsumer);
 assertEquals(10, myConsumer.total);
 }
 @Test
 public void basicIteratorRemoval() {
 list.addAll(Arrays.asList(0, 1, 2, 3, 4));
 Iterator<Integer> iter = list.iterator();
 iter.next();
 iter.next();
 iter.remove();
 assertEquals(4, list.size());
 iter = list.iterator();
 iter.next();
 iter.remove();
 assertEquals(3, list.size());
 assertEquals(Integer.valueOf(2), list.get(0));
 assertEquals(Integer.valueOf(3), list.get(1));
 assertEquals(Integer.valueOf(4), list.get(2));
 }
 @Test
 public void enhancedIteratorTraversal() {
 list.addAll(Arrays.asList(0, 1, 2, 3, 4));
 ListIterator<Integer> iter = list.listIterator();
 assertFalse(iter.hasPrevious());
 for (int i = 0; i < list.size(); i++) {
 assertTrue(iter.hasNext());
 assertEquals(Integer.valueOf(i), iter.next());
 }
 assertFalse(iter.hasNext());
 for (int i = 4; i >= 0; i--) {
 assertTrue(iter.hasPrevious());
 assertEquals(Integer.valueOf(i), iter.previous());
 }
 iter = list.listIterator(2);
 assertEquals(Integer.valueOf(2), iter.next());
 assertEquals(Integer.valueOf(2), iter.previous());
 iter = list.listIterator(3);
 assertEquals(Integer.valueOf(3), iter.next());
 assertEquals(Integer.valueOf(4), iter.next());
 assertFalse(iter.hasNext());
 assertTrue(iter.hasPrevious());
 }
 @Test
 public void enhancedIteratorAddition() {
 list.addAll(Arrays.asList(1, 2, 3));
 ListIterator<Integer> iter = list.listIterator();
 iter.add(0);
 while (iter.hasNext()) {
 iter.next();
 }
 iter.add(4);
 iter = list.listIterator();
 for (int i = 0; i < list.size(); i++) {
 assertEquals(Integer.valueOf(i), iter.next());
 }
 iter = list.listIterator(2);
 iter.add(10);
 assertEquals(Integer.valueOf(10), list.get(2));
 }
 @Test
 public void findFailingIterat() {
 list.addAll(getIntegerList(345_850));
 Iterator<Integer> iterator = list.iterator();
 int counter = 0;
 while (iterator.hasNext()) {
 iterator.next();
 // Remove every 2nd element:
 if (counter % 10 == 0) {
 iterator.remove();
 }
 counter++;
 }
 }
 @Test
 public void bruteForceIteratorRemove() throws Exception {
 list.addAll(getIntegerList(1000));
 int counter = 0;
 List<Integer> arrayList = new ArrayList<>(list);
 Iterator<Integer> iter = list.iterator();
 Iterator<Integer> arrayListIter = arrayList.iterator();
 int totalIterations = 0;
 while (iter.hasNext()) {
 iter.next();
 arrayListIter.next();
 if (counter % 10 == 0) {
 try {
 iter.remove();
 } catch (IllegalStateException ex) {
 throw new Exception(ex);
 }
 arrayListIter.remove();
 counter = 0;
 } else {
 counter++;
 }
 if (!listsEqual(list, arrayList)) {
 throw new IllegalStateException(
 "totalIterations = " + totalIterations);
 }
 totalIterations++;
 }
 }
 @Test
 public void bruteForceRemoveObjectBeforeIteratorRemove() {
 LinkedList<String> ll = new com.github.coderodde.util.LinkedList<>();
 ll.add("a");
 ll.add("b");
 ll.add("c");
 ll.add("d");
 ll.remove("b");
 ll.remove("c");
 ll.remove("d");
 ll.remove("a");
 }
 @Test
 public void findFailingRemoveObject() {
 java.util.LinkedList<Integer> referenceList = 
 new java.util.LinkedList<>();
 list.addAll(getIntegerList(10));
 referenceList.addAll(list);
 Integer probe = list.get(1);
 list.remove(probe);
 referenceList.remove(probe);
 Iterator<Integer> iterator1 = list.iterator();
 Iterator<Integer> iterator2 = referenceList.iterator();
 Random random = new Random(100L);
 while (!list.isEmpty()) {
 if (!iterator1.hasNext()) {
 if (iterator2.hasNext()) {
 throw new IllegalStateException();
 }
 iterator1 = list.iterator();
 iterator2 = referenceList.iterator();
 continue;
 }
 iterator1.next();
 iterator2.next();
 if (random.nextBoolean()) {
 iterator1.remove();
 iterator2.remove();
 assertTrue(listsEqual(list, referenceList));
 }
 }
 assertTrue(listsEqual(list, referenceList));
 }
 @Test
 public void iteratorAdd() {
 list.addAll(getIntegerList(4));
 ListIterator<Integer> iterator = list.listIterator(1);
 assertEquals(1, iterator.nextIndex());
 assertEquals(0, iterator.previousIndex());
 iterator.next();
 assertEquals(2, iterator.nextIndex());
 assertEquals(1, iterator.previousIndex());
 iterator.add(Integer.valueOf(100));
 assertEquals(Integer.valueOf(0), list.get(0));
 assertEquals(Integer.valueOf(1), list.get(1));
 assertEquals(Integer.valueOf(100), list.get(2));
 assertEquals(Integer.valueOf(2), list.get(3));
 assertEquals(Integer.valueOf(3), list.get(4));
 }
 @Test
 public void bruteForceIteratorTest() {
 list.addAll(getIntegerList(100));
 List<Integer> referenceList = new java.util.LinkedList<>(list);
 ListIterator<Integer> iterator1 = list.listIterator(2);
 ListIterator<Integer> iterator2 = referenceList.listIterator(2);
 long seed = System.currentTimeMillis();
 Random random = new Random(seed);
 System.out.println("- bruteForceIteratorTest: seed = " + seed);
 while (iterator1.hasNext()) {
 if (!iterator2.hasNext()) {
 fail("Iterator mismatch on hasNext().");
 }
 iterator1.next();
 iterator2.next();
 int choice = random.nextInt(10);
 if (choice < 2) {
 Integer integer = Integer.valueOf(random.nextInt(100));
 iterator1.add(integer);
 iterator2.add(integer);
 assertTrue(listsEqual(list, referenceList));
 } else if (choice == 2) {
 iterator1.remove();
 iterator2.remove();
 assertTrue(listsEqual(list, referenceList));
 } else if (choice < 6) {
 if (iterator1.hasPrevious()) {
 iterator1.previous();
 }
 if (iterator2.hasPrevious()) {
 iterator2.previous();
 }
 } else {
 if (iterator1.hasNext()) {
 iterator1.next();
 }
 if (iterator2.hasNext()) {
 iterator2.next();
 }
 }
 }
 if (iterator2.hasNext()) {
 fail("Java List iterator has more to offer.");
 }
 }
 @Test
 public void indexOf() {
 list.add(1);
 list.add(2);
 list.add(3);
 list.add(3);
 list.add(2);
 list.add(1);
 assertEquals(0, list.indexOf(1));
 assertEquals(1, list.indexOf(2));
 assertEquals(2, list.indexOf(3));
 assertEquals(3, list.lastIndexOf(3));
 assertEquals(4, list.lastIndexOf(2));
 assertEquals(5, list.lastIndexOf(1));
 }
 class MyIntegerConsumer implements Consumer<Integer> {
 List<Integer> ints = new ArrayList<>();
 @Override
 public void accept(Integer t) {
 ints.add(t);
 }
 }
 @Test
 @SuppressWarnings("empty-statement")
 public void basicSpliteratorUsage() {
 list.addAll(getIntegerList(10_000));
 Spliterator<Integer> spliterator1 = list.spliterator();
 Spliterator<Integer> spliterator2 = spliterator1.trySplit();
 //// spliterator 2 : spliterator 1
 assertEquals(5000, spliterator1.getExactSizeIfKnown());
 assertEquals(5000, spliterator2.getExactSizeIfKnown());
 assertTrue(spliterator2.tryAdvance(
 i -> assertEquals(list.get(0), Integer.valueOf(0))));
 assertTrue(spliterator2.tryAdvance(
 i -> assertEquals(list.get(1), Integer.valueOf(1))));
 assertTrue(spliterator2.tryAdvance(
 i -> assertEquals(list.get(2), Integer.valueOf(2))));
 assertTrue(spliterator1.tryAdvance(
 i -> assertEquals(list.get(5000), Integer.valueOf(5000))));
 assertTrue(spliterator1.tryAdvance(
 i -> assertEquals(list.get(5001), Integer.valueOf(5001))));
 assertTrue(spliterator1.tryAdvance(
 i -> assertEquals(list.get(5002), Integer.valueOf(5002))));
 //// spliterator 3 : spliterator 2 : splitereator 1
 Spliterator<Integer> spliterator3 = spliterator2.trySplit();
 assertEquals(4997, spliterator1.getExactSizeIfKnown());
 assertTrue(spliterator3.tryAdvance(
 i -> assertEquals(list.get(3), Integer.valueOf(3))));
 assertTrue(spliterator3.tryAdvance(
 i -> assertEquals(list.get(4), Integer.valueOf(4))));
 assertTrue(spliterator3.tryAdvance(
 i -> assertEquals(list.get(5), Integer.valueOf(5))));
 //// 
 MyIntegerConsumer consumer = new MyIntegerConsumer();
 while (spliterator1.tryAdvance(consumer));
 for (int i = 0; i < consumer.ints.size(); i++) {
 Integer actualInteger = consumer.ints.get(i);
 Integer expectedInteger = 5003 + i;
 assertEquals(expectedInteger, actualInteger);
 }
 }
 @Test
 public void spliteratorForEachRemaining() {
 list.addAll(getIntegerList(10_000));
 Spliterator<Integer> split = list.spliterator();
 MyIntegerConsumer consumer = new MyIntegerConsumer();
 split.forEachRemaining(consumer);
 for (int i = 0; i < 10_000; i++) {
 assertEquals(Integer.valueOf(i), consumer.ints.get(i));
 }
 }
 @Test
 public void spliteratorForEachRemainingTwoSpliterators() {
 list.addAll(getIntegerList(10_000));
 Spliterator<Integer> splitRight = list.spliterator();
 Spliterator<Integer> splitLeft = splitRight.trySplit();
 MyIntegerConsumer consumerRight = new MyIntegerConsumer();
 MyIntegerConsumer consumerLeft = new MyIntegerConsumer();
 splitRight.forEachRemaining(consumerRight);
 splitLeft.forEachRemaining(consumerLeft);
 for (int i = 0; i < 5_000; i++) {
 assertEquals(Integer.valueOf(i), consumerLeft.ints.get(i));
 }
 for (int i = 5_000; i < 10_000; i++) {
 assertEquals(Integer.valueOf(i), consumerRight.ints.get(i - 5_000));
 }
 }
 @Test
 public void spliteratorForEachRemainingWithAdvance() {
 list.addAll(getIntegerList(10_000));
 Spliterator<Integer> rightSpliterator = list.spliterator();
 assertTrue(
 rightSpliterator.tryAdvance(
 i -> assertEquals(Integer.valueOf(0), i)));
 Spliterator<Integer> leftSpliterator = rightSpliterator.trySplit();
 assertEquals(4_999, rightSpliterator.getExactSizeIfKnown());
 assertEquals(5_000, leftSpliterator.getExactSizeIfKnown());
 // Check two leftmost elements of the left spliterator:
 assertTrue(leftSpliterator.tryAdvance(
 i -> assertEquals(Integer.valueOf(1), i)));
 assertTrue(leftSpliterator.tryAdvance(
 i -> assertEquals(Integer.valueOf(2), i)));
 // Check two leftmost elements of the right splliterator:
 assertTrue(rightSpliterator.tryAdvance(
 i -> assertEquals(Integer.valueOf(5_000), i)));
 assertTrue(rightSpliterator.tryAdvance(
 i -> assertEquals(Integer.valueOf(5_001), i)));
 }
 @Test
 public void spliterator() {
 list.addAll(getIntegerList(6_000));
 Spliterator split = list.spliterator();
 assertEquals(6_000L, split.getExactSizeIfKnown());
 assertEquals(6_000L, split.estimateSize());
 assertTrue(split.tryAdvance((i) -> assertEquals(list.get((int) i), i)));
 assertTrue(split.tryAdvance((i) -> assertEquals(list.get((int) i), i)));
 assertEquals(5998, split.getExactSizeIfKnown());
 // 5998 elements left / 2 = 2999 per spliterator:
 Spliterator leftSpliterator = split.trySplit();
 assertNotNull(leftSpliterator);
 assertEquals(2999, split.getExactSizeIfKnown());
 assertEquals(2999, leftSpliterator.getExactSizeIfKnown());
 //// leftSpliterator = [1, 2999]
 for (int i = 2; i < 3000; i++) {
 Integer integer = list.get(i);
 assertTrue(
 leftSpliterator.tryAdvance(
 (j) -> assertEquals(integer, j)));
 }
 //// split = [3001, 5999]
 assertTrue(split.tryAdvance(i -> assertEquals(2999, i)));
 assertTrue(split.tryAdvance(i -> assertEquals(3000, i)));
 assertTrue(split.tryAdvance(i -> assertEquals(3001, i)));
 while (split.getExactSizeIfKnown() > 0) {
 split.tryAdvance(i -> {});
 }
 assertFalse(split.tryAdvance(i -> {}));
 }
 @Test
 public void bruteforceSpliterator() {
 list.addAll(getIntegerList(1_000_000));
 Collections.<Integer>shuffle(list);
 List<Integer> newList = 
 list.parallelStream()
 .map(i -> 2 * i)
 .collect(Collectors.toList());
 assertEquals(newList.size(), list.size());
 for (int i = 0; i < list.size(); i++) {
 Integer integer1 = 2 * list.get(i);
 Integer integer2 = newList.get(i);
 assertEquals(integer1, integer2);
 }
 }
 private static final String SERIALIZATION_FILE_NAME = "LinkedList.ser";
 @Test
 public void serialization() {
 list.add(10);
 list.add(13);
 list.add(12);
 try {
 File file = new File(SERIALIZATION_FILE_NAME);
 FileOutputStream fos = new FileOutputStream(file);
 ObjectOutputStream oos = new ObjectOutputStream(fos);
 oos.writeObject(list);
 oos.flush();
 oos.close();
 FileInputStream fis = new FileInputStream(file);
 ObjectInputStream ois = new ObjectInputStream(fis);
 com.github.coderodde.util.LinkedList<Integer> ll = 
 (com.github.coderodde.util.LinkedList<Integer>)
 ois.readObject();
 ois.close();
 boolean equal = listsEqual(list, ll);
 assertTrue(equal);
 if (!file.delete()) {
 file.deleteOnExit();
 }
 } catch (IOException | ClassNotFoundException ex) {
 fail(ex.getMessage());
 } 
 }
 @Test
 public void bruteforceSerialization() {
 for (int i = 0; i < 20; i++) {
 list.addAll(getIntegerList(i));
 try {
 File file = new File(SERIALIZATION_FILE_NAME);
 FileOutputStream fos = new FileOutputStream(file);
 ObjectOutputStream oos = new ObjectOutputStream(fos);
 oos.writeObject(list);
 oos.flush();
 oos.close();
 FileInputStream fis = new FileInputStream(file);
 ObjectInputStream ois = new ObjectInputStream(fis);
 com.github.coderodde.util.LinkedList<Integer> ll = 
 (com.github.coderodde.util.LinkedList<Integer>)
 ois.readObject();
 ois.close();
 boolean equal = listsEqual(list, ll);
 assertTrue(equal);
 if (!file.delete()) {
 file.deleteOnExit();
 }
 } catch (IOException | ClassNotFoundException ex) {
 fail(ex.getMessage());
 } 
 list.clear();
 }
 }
 private static boolean listsEqual(
 com.github.coderodde.util.LinkedList<Integer> list1, 
 java.util.List<Integer> list2) {
 if (list1.size() != list2.size()) {
 return false;
 }
 Iterator<Integer> iter1 = list1.iterator();
 Iterator<Integer> iter2 = list2.iterator();
 while (iter1.hasNext() && iter2.hasNext()) {
 Integer int1 = iter1.next();
 Integer int2 = iter2.next();
 if (!int1.equals(int2)) {
 return false;
 }
 }
 if (iter1.hasNext() || iter2.hasNext()) {
 throw new IllegalStateException();
 }
 return true;
 } 
 private static List<Integer> getIntegerList() {
 return getIntegerList(100);
 }
 private static List<Integer> getIntegerList(int length) {
 List<Integer> list = new ArrayList<>(length);
 for (int i = 0; i < length; i++) {
 list.add(i);
 }
 return list;
 }
}

Critique request

I would love to receive any comments improving my unit tests.

Answer 1

A few things to consider...

Naming

Naming is important, code is read a lot more than it is written and anything that makes the code easier to read helps. One element of that is consistency, which is something that your test names don't have. Some of them start with test and some of them don't. Some of them are quite descriptive about what's being tested testAddCollectionThreeElementsToEmptyList, however others aren't (testAdd,spliterator). Try to settle on a style and be consistent with the naming.

Another example of naming that could be improved in bruteforceSpliterator:

Integer integer1 = 2 * list.get(i);
Integer integer2 = newList.get(i);
assertEquals(integer1, integer2);

Personally, I'd have just passed the values into the assertEquals, without creating the local variables. However, if you are going to create them, then they should be at least as descriptive as the thing they're replacing, each level of indirection adds unnecessary cognitive processing to understand the code. listValueX2 and newListValue may have been better choices.

Setup

It struct me as odd that you had a list.clear() call in your setUp. I'd expect the list to be clear when it's constructed. Having it in the setup makes it seem as if the list is needs to be cleared before it can be used.

Test focus

Tests that try to do too much can lose the intention of the test in the noise. In your testAdd method, at the start of the test you verify that the list is empty and has a size of 0. This has nothing to do with testing add. Consider putting them in their own test instead.

Test explicitly as in testAddCollectionAtIndex

Consider being more explicit when you can be. If you know the list should contain 8 items, then using 8, rather than list.size() can make the test easier to mentally process.

AssertJ - containsExactly

There are a few tests that compare the contents of your list against the expected contents of the list. So, for example in testAddCollectionThreeElementsToEmptyList you do:

assertEquals(3, list.size());
for (int i = 0; i < list.size(); i++) {
 assertEquals(Integer.valueOf(i + 1), list.get(i));
}

I prefer to use AssertJ for my assertions, because I find the fluent interface easier to read. It has quite a lot of extensions that make working with collections very pleasant. Instead of the above, you can combine the size and element comparison into a single assertion that gives very descriptive feedback on failure:

assertThat(list).containsExactly(1,2,3);

Files

Where you can, you want to try to avoid using the file system it tends to be a can of worms that can lead to unpredictable failures. Rather than using FileOutputStream and FileInputStream in your serialization test, consider using the Byte versions instead:

ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
// ...
ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bis);

Exceptions

You don't need to catch exceptions that you want to fail your tests, the testing framework will catch the exceptions and convert them into an appropriate message for you. So, rather than doing this:

} catch (IOException | ClassNotFoundException ex) {
 fail(ex.getMessage());
}

Consider instead just declaring the the method:

public void serialization() throws IOException, ClassNotFoundException {

Test coverage

I ran test coverage against your the list in your previous question. You're running at about 71% method and line coverage. You may find it useful to run a coverage tool (the community edition of Intellij has a built in one) to see if it gives you some helpful insights about sections of your code that are lacking in coverage.