Unit Tests: Exercise

  • Write simple unit tests using the JUnit framework.

Exercise complete the implementation of the following unit tests:

@Test
@DisplayName("get() returns the default value after IndexedList is instantiated.")
void testGetAfterConstruction() {
  // TODO Implement me!
}

@Test
@DisplayName("put() changes the default value after IndexedList is instantiated.")
void testPutChangesValueAfterConstruction() {
  // TODO Implement me!
}

@Test
@DisplayName("put() overwrites the existing value at given index to provided value.")
void testPutUpdatesValueAtGivenIndex() {
  // TODO Implement me!
}

When you run your tests, they must all pass.

Solution 
@Test
@DisplayName("get() returns the default value after IndexedList is instantiated.")
void testGetAfterConstruction() {
  IndexedList<Integer> numbers = new ArrayIndexedList<>(5, 10);
  for (int index = 0; index < numbers.length(); index++) {
    assertEquals(10, numbers.get(index));
  }
}

@Test
@DisplayName("put() changes the default value after IndexedList is instantiated.")
void testPutChangesValueAfterConstruction() {
  IndexedList<Integer> numbers = new ArrayIndexedList<>(5, 10);
  numbers.put(2, 7);
  assertEquals(7, numbers.get(2));
}

@Test
@DisplayName("put() overwrites the existing value at given index to provided value.")
void testPutUpdatesValueAtGivenIndex() {
  IndexedList<Integer> numbers = new ArrayIndexedList<>(5, 10);
  numbers.put(1, 8);
  assertEquals(8, numbers.get(1));
  numbers.put(1, -5);
  assertEquals(-5, numbers.get(1));
}

Exercise What other unit tests can we add to IndexedListTest? You don't need to write the tests, only describe them.

Solution

Here are some ideas:

  • Test get and length have no side effects; that is, calling it will not cause any changes to the data structure.
  • Test put has no unintended effects; for example, it does not change the size of the data structure, nor does it change a value at another index.