Assignment 1 - History and Introduction

Programming Exercise - Fibonnaci Numbers

The goal of the first programming exercise is to get you aquainted with a Java build tool, a test framework and TDD, and work a tiny bit with the Java class BigInteger. We will later in the course, when we will cover security need BigInteger calculations.

To complete this part of the assignment, you must download the gradle-spock-intro.zip and unpack.

While the assignment has links to Gradle, Spock and Groovy, it should not be necessary to study those in details. Instructions are included in the assignment text.

Introduction

In this first exercise to get familiar with Gradle, an enterprise setup using packages and a testing framework, you must implement the Fibonnacci calculator in the NumberCalculations class.

The Fibonnacci numbers are defined like this:

The first fibbonnacci number is 1
The second fibbonnacci number is 1
The n’th fibbonnacci number is the sum of the (n-1)'th and the (n-2)'th

Gradle

Gradle is a powerfull build tool used for building and executing larger Java projects. It comes with a Gradle wrapper, so it can bootstrap itself. The build specification is in the file build.gradle, but don’t worry, it is set up for you.

You can run the application using the command

./gradlew run

It will compile and execute the Main method in the Main class, located in src/main/java/dk/sdu/imada/Main.java

You can also use Gradle to execute the tests. For this use

./gradlew test

Tip	If you are on windows, use gradlew.bat instead of gradlew

Warning

There is no need to compile your Java class with javac, you should let Gradle do the compilation and test for you.

Spock Tests

Spock is a test framework, that using the Groovy language is very powerfull and readable to write test specifications in.

You can find the tests written for the Fibonnacci calculation in the file src/test/groovy/dk/sdu/imada/NumberCalculationsSpec.groovy

The Tasks

Run the tests using:

./gradlew test

Open the test report and look at the test results. You can now working in a TDD (Test Driven Development) way. Take a look at the first test, which says 'Check exception is thrown for 0 input'. It indicates an exception must be thrown if the input is smaller than 1. If you insert this into the calculateFibonnacci method:

if( number < 1) {
    throw new InputException("Input must be >= 1");
}

And run the tests again, you should see one test passing!

Implement code for to make each test pass, running the tests regularly.

What to turn in?

In the NumberCalculationsSpec on line 52, you can replace the 0 with the value you must turn in that will let the test pass (when the other tests also pass). You can also find the value in the test report. The other thing you must turn in is the source code of the NumberCalculations class.

Extra credit exercise

In the Spock test, the last test method is annotated with @Ignore. Try to remove this annotation and run the tests. They will likely just hang for a long time! (Feel free to abort)

Try to implement caching, so the method remembers previously calculated results, and see if you can speed it up.

Assignment: Assignment 1 - History and Introduction