Lab 6: JUnit Testing

Overview

Having thorough tests can ensure the behavior of a class matches its specification, but writing thorough tests can be challenging. In this assignment you will gain experience writing unit tests for an AutoCompleter interface and use it to test your own implementation of the interface.

Video introduction for the lab

Assignment

AutoCompleter interface

The AutoCompleter interface has the following methods:

• boolean add(String word) — returns true if word is added to the object (a word should not be added if it is already in the auto completer). If word is null or an empty string, an IllegalArgumentException is thrown.
• int size() — returns the number of items in the auto completer.
• boolean exactMatch(String target) — returns true if target is found in the auto completer. If target is null or an empty string, the method returns false.
• String[] allMatches(String prefix) — returns an array of all the strings in the object that begin with the prefix. If prefix is an empty string, an array of all the strings in the auto completer are returned. If prefix is null, an empty array is returned.
• String getBackingClass() — returns a String indicating the fully qualified name of the data structure used to store the words for the AutoCompleter. E.g., "java.util.ArrayList".
• static String format(long nanoseconds) — returns a human-friendly string representing the number of nanoseconds. The format of the string must be consistent with the examples below. Select the first line where the first number is at least 1. Note: this method is declared static which means that it should be implemented in the interface. If a negative value is supplied, the method should throw an IllegalArgumentException.
  • 2 days 5 hours 32 minutes
  • 14 hours 1 minute 8 seconds
  • 42 minutes 55.3 seconds
  • 18.8 seconds
  • 998.8 milliseconds
  • 318.8 microseconds
  • 7 nanoseconds

You must implement the static format() method and write complete javadocs for all the methods in AutoCompleter.

Unordered List Implementation

You must create a class, UnorderedList, that implements the AutoCompleter interface using an unordered list. Your class must have only one private attribute: private final List<String> items that is assigned via a one-argument constructor. Note: the constructor should ensure that no duplicates are in the list passed to the constructor.

List<String> unique = items.stream().distinct().toList();
items.clear();
items.addAll(unique);

Testing

You must create JUnit tests for all of the methods in the AutoCompleter interface. These tests should be rigorous and ensure all methods behave as specified in the requirements. If the behavior of specific methods are not completely specified, please ask your instructor for clarification.

Use the tests to ensure your UnorderedList implementation conforms to the requirements.

Your instructor may verify your tests by providing multiple faulty implementations to see if your tests catch the errors embedded in the faulty implementations.

Acknowledgement

This laboratory assignment, developed by Dr. Chris Taylor.