Explore writing unit tests for Java applications using JUnit, delve into JUnit organization, assertions, quality practices, design relevance, refactoring, and using mock objects for dependencies.

Pragmatic Unit Testing in Java 8 with Junit by The Pragmatic Programmer.png

junit.tar.gz

java

test2

test4 - Our first passing test

test6

test14

test16-branch-persistence

AssertTest-13

test15

test15-profile

test15-ProfilePoolTest

test16-BearingTest

test16-RectangleTest

test16-SparseTest

test16-TransmissionTest

test16-ProfileTest

test20m-ProfileTest

test21-Profile

big1-Profile

big1-MatchSet

big4-MatchSetTest

big4-MatchSet

big6

mock-2-AddressRetrieverTest

mock-4-AddressRetrieverTest

mock-5-AddressRetrieverTest

test1-SearchTest

test3-SearchTest

tdd-1-ProfileTest.java 

tdd-2-ProfileTest.java

tdd-3-ProfileTest.java

tdd-4-Profile.java

tdd-5-ProfileTest.java

tdd-9-ProfileTest.java

tdd-10-ProfileTest.java

tdd-10-AnswerTest.java

tdd-11-ProfileTest.java

tdd-12-ProfileTest.java

tdd-14-ProfileTest.java

tdd-15-ProfileTest.java

thread-2-ProfileMatcherTest

thread-3-ProfileMatcherTest

thread-4-ProfileMatcherTest

test16-branch-persistence-redesign-QCTest

AssertHamcrest-13

test16-branch-persistence-redesign-StatCompilerTest

test16-ProfilePoolTest

test15-ProfilePoolTest-copy 16

test3-SearchTest-ContainsMatches

tdd-11-ProfileTest.java-Supporting Multiple Answers

thread-2-ProfileMatcherTest-Testing Multithreaded Code

test2-Our First passing test

test4 - AAA your way to a test

test2-final-intro-junit

In this course, you will learn how to write a unit test for Java applications using JUnit. You'll start by covering unit-testing foundations, which provide you with a starter set of information about writing basic tests in JUnit. You’ll learn about JUnit organization and assertions, and you’ll pick up a few core quality practices for unit testing such as the Right BICEP and the CORRECT way. 

Towards the end, the bigger design picture focuses on the relevance of design to unit testing and vice versa. You’ll refactor your tests, and you’ll learn how to use mock objects to deal with trouble-some dependencies.

Pragmatic Unit Testing in Java 8 with JUnit

We were able to refactor this class so that most of its code doesn’t directly interact with a `QuestionController` instance, which in turn lets us write fast tests for the bulk of its logic. We were left with one method, `questionText()`, that interacts with a `controller` object. Let’s test that method:

public Map<Integer,String> questionText(List<BooleanAnswer> answers) {
  Map<Integer,String> questions = new HashMap<>();
  answers.stream().forEach(answer -> {
      if (!questions.containsKey(answer.getQuestionId()))
        questions.put(answer.getQuestionId(), 
            controller.find(answer.getQuestionId()).getText()); });
  return questions;
}

The `questionText()` method takes a list of `answer` objects and returns a **hashmap** of unique answer IDs to the corresponding question text.
 
>To paraphrase the `forEach` loop: for each answer ID that’s not already represented in the responses map, find the corresponding question using the `controller` and put the found question’s text into the responses map.

# The issues with the controller

The trouble with writing tests for `questionText()` is the controller, which talks to a Postgres database using the Java Persistence API (JPA). Our first question about the `QuestionController` controller class is do we trust it and understand how it behaves? We’d like to make sure by writing some tests for it. Here’s the code for the class:

Learn how to write tests in order to test databases.

Testing Databases

Before We Begin

JUnit Test Foundations

Digging Deeper into JUnit Assertions

Organizing Your Tests

Mastering Manic Mnemonics!

What to Test: The Right-BICEP

Boundary Conditions: The CORRECT Way

The Bigger Design Picture

Bigger Design Issues

Using Mock Objects

Refactoring Tests

The Bigger Unit-Testing Picture

Testing Some Tough Stuff

Testing on a Project

Wrapping Up

Appendix - Setting up JUnit

Testing Databases