Lecture 4

JUnit�Compilation Steps

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Some slides were borrowed from Josh Hug and Adam Jundt

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Testing

Black-box Testing

• You don’t know (or you pretend you don’t know) how something is implemented
• You test only based on inputs and outputs

Clear-box Testing (asa “white-box testing”)

• If you can look inside the black box and see how a method is implemented, you can do more detailed testing

Why bother?? http://stackoverflow.com/questions/10858990/why-use-junit-for-testing

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Unit (micro)-testing

• Whether you are doing black-box or clear-box testing, you should test every unit of a software system.
• What is a unit? In object-oriented programming, usually a software unit is taken to be a single method.
• So: we should test every method of every class in the software.
• JUnit is a widely used framework for unit testing of Java software.

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Test-Driven Development (TDD)

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Steps to developing according to TDD:

• Identify a new feature.
• Write a unit test for that feature.
• Run the test. It should fail. (RED)
• Write code that passes test. (GREEN)
• Implementation is certifiably good!
• Optional: Refactor code to make it faster, cleaner, etc.

�Not required but testing is always needed. �

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Problem to solve.

• Swap characters in the string:
• “Marina” -> “aniraM”
• “Class” -> “ssalC”

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Idea?

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Did everything make sense?

A: Yes

B: Almost, need to practice now

C: More or less, need to review (and then practice)

D: Mostly lost

E: Completely lost

@BeforeEach, @AfterEach, @beforeAll

• @BeforeEach
• annotation is used to signal that the annotated method should be executed before each invocation.
• @AfterEach
• is used to signal that the annotated method should be executed after each @Test.

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• @BeforeAll
• runs once before any of the test methods in the class.

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Compilation

(demo)

Why bother with class file?

Why make a class file at all?

• .class file has been type checked. Distributed code is safer.
• .class files are ‘simpler’ for machine to execute. Distributed code is faster.
• Platform independent.

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public class CarLauncher {

public static void main(String[] args) {

Car audi;

new Car(40);

audi = new Car(50);

Car honda = new Car(4);

audi.blowUp();

honda.blowUp();

}

} //Link

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class Car {

int speed;

public Car(int sp){

speed = sp;

}

public void blowUp() { System.out.println("baaaam!: " + speed);

}

}

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