Slides used in the February 2017 meetup of the Java Beginners Meetup in Utrecht. The covered topics were testing and TDD. Some exercises to practice are also referred.

1. An introduction to testing and TDD
Patrick Kostjens
February 7, 2017
Java Beginners Meetup

2. Table of contents
1. Introduction
2. Test Driven Development
3. Unit testing in Java
4. Exercise 1
5. Exercise 2
1

3. Introduction

4. About me
Patrick Kostjens
Software Developer
2

5. Why testing?
To build better software faster
3

6. Better software
• Fewer bugs
• Easier to maintain
• Easier to change
• Safer to change
4

7. How to test?
Write code that checks if other code does what it is
supposed to.
5

8. Types of testing
1. Unit testing
2. Integration testing
3. System testing
4. Acceptance testing
6

9. Testing concepts
• Mocking
• e2e
• TDD
• BDD
7

10. Test Driven Development

11. Brief introduction
Writing tests to check if your code works seems good, right?
8

12. Brief introduction
Writing tests to check if your code works seems good, right?
But, maybe we are only testing what we expect to happen.
8

13. Brief introduction
Writing tests to check if your code works seems good, right?
But, maybe we are only testing what we expect to happen.
What if we write our tests before we write (bits of) code?
8

14. Brief introduction
Writing tests to check if your code works seems good, right?
But, maybe we are only testing what we expect to happen.
What if we write our tests before we write (bits of) code?
Test Driven Development
8

15. TDD workflow
9

16. Why TDD?
• No influence from knowledge gained while implementing
10

17. Why TDD?
• No influence from knowledge gained while implementing
• Immediately know if every bit of code works
10

18. Why TDD?
• No influence from knowledge gained while implementing
• Immediately know if every bit of code works
• Keep code as simple as possible
10

19. Why TDD?
• No influence from knowledge gained while implementing
• Immediately know if every bit of code works
• Keep code as simple as possible
• Make code easy to test
10

20. Why TDD?
• No influence from knowledge gained while implementing
• Immediately know if every bit of code works
• Keep code as simple as possible
• Make code easy to test
• Catch bugs early
10

21. Unit testing in Java

22. Tools and frameworks
Frameworks:
• JUnit
• TestNG
Tools:
• Mockito
• EasyMock
• Powermock
• Hamcrest
11

23. Simple test in JUnit
import org.junit.Test;
import org.junit.Assert;
public class SimpleTest {
@Test
public void test1Returns1 () {
Assert.assertEquals("1",
getAnswer (1));
}
}
12

24. Test preparation
public class PrepareTest {
private FizzBuzz testObject;
@Before
public void setup() {
testObject = new FizzBuzz ();
}
@Test
//...
}
13

25. Exercise 1

26. Fizz Buzz project
Take repository at:
https://github.com/patrickkostjens/fizz-buzz-exercise
Install and run using README
14

27. Fizz Buzz rules
• Dividable by 3? Fizz
• Dividable by 5? Buzz
• Dividable by 3 and 5? Fizz Buzz
• None of the above? Just a number
Exercise
Given a number, return the Fizz Buzz answer for that
number.
15

28. Easy, right?
Fizz Buzz seems to be very easy
yet
there are many solutions
See: https://ditam.github.io/posts/fizzbuzz/
16

29. Exercise 2

30. Bowling scoring system
• No project setup available
• Don’t build an interface
• Start simple!
• Try to do TDD
17

31. Thank you!
17