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Quiz Game - Part 06

Continue to work on the Maven project started as exercise in the first lesson.

Create a stateless EJB called QuizEjb with the following methods:

  • public long createQuiz( long subCategoryId, String question, String firstAnswer, String secondAnswer, String thirdAnswer, String fourthAnswer, int indexOfCorrectAnswer )

    Create a new quiz, and return the id of the newly generated entity.

  • public List<Quiz> getQuizzes()

    Return all existing quizzes.

  • public Quiz getQuiz(long id)

    Return the quiz with the given id.

  • public List<Quiz> getRandomQuizzes(int n, long categoryId)

    Return n quizzes, chosen at random, without replacement (i.e., they should be all unique, without duplicates). If there exist less than n quizzes in the database, throw an exception. Note: implementing this method in an efficient way is not trivial, as databases usually do not natively support random reads.

Create a singleton EJB called DefaultDataInitializerEjb which is initialized at startup. Such EJB should create at least 2 categories, at least 5 subcategories, and at least 10 questions. Each category should have at least 5 questions under it.
Create meaningful questions and categories, as those will be used as the default ones in the quiz game.

In the test folder, create a EjbTestBase abstract class which is responsible to init Arquillian and reset the database before each test case. The test classes will extend this abstract class.

Write a QuizEjbTest test class in which you inject a reference to QuizEjb. Write the following tests:

  • testNoQuiz: verify that there is no existing quiz. Note: this test would fail if you do not reset the database in EjbTestBase, as the singleton DefaultDataInitializerEjb would create at least 10 questions.

  • testCreateQuiz: create one quiz. Retrieve all quizzes, and verify that there is only 1. Verify this is the one you just created (e.g., if the question fields are the same).

  • testNotEnoughQuizzes: create 3 quizzes. Try to retrieve 5 quizzes at random. Verify that this action throws an exception.

  • testGetRandomQuizzes: create 3 quizzes. In a loop repeated 50 times, sample 2 quizzes at random from the database. At each of the 50 iterations, verify that those 2 quizzes are different. After the 50 iterations, verify that each quiz was sampled at least once.
    Note: it might be that, due to randomness, this test fails. But such should have an extremely low probability.

Write a DefaultDataInitializerEjbTest test class that does NOT extend EjbTestBase, as it should not reset the database before the tests are run. Without injecting a reference to DefaultDataInitializerEjb, write a test in which you verify that in the database there is at least 1 category, 1 subcategory and 1 quiz.

Solutions to this exercise can be found in the intro/exercise-solutions/quiz-game/part-06 module.