Tennis Kata: Typescript, Jasmine and BDD

This Kata provides a starting point for practicing Behavior Driven Development (BDD) with Typescript as programming language and Jasmine to specify your tests.

If you don't know the term BDD yet, read this blog post from the inventor of the term or the behaviour-driven.org wiki. In summary BDD it is about writing tests first and additionally documenting the behavioural intent of the system with these tests.

Preparation

Prepare your system

You need a copy of this project (you can fork or clone it). To build and run this project you need to install Node.js.

Get your dev environment ready

1. Open a console at the root of your local repository (where this README is placed)

2. Run npm install. Npm is node's package manager. "npm install" downloads all node modules specified in package.json. The modules are stored into the folder "node_modules". The modules are needed for building this project and executing the tests.

3. Run grunt init Grunt is a javscript task runner. The tasks are defined in GruntFile.js. The "init" task will download Typescript declaration files (d.ts) specified in tsd.json.

4. Run grunt This will run the default "watch" task. On a source file change (*.ts) the files are compiled and the tests are executed.

5. Open your favorite text editor with the following files:

• TennisGame.ts - The given interface for this kata. Should not be modified.
• TennisGameImpl.ts - Your implementation of the TennisGame interface goes here.
• TennisGameSpec.ts - Your test code goes here.

1. Edit "TennisGameImpl.ts" by modifying the return value. Look at your console: The file is compiled and the tests are run. You should see that one test fails.

Congratulations you can now start the Typescript Tennis Kata. As a first step, try to fix the failing test by providing the expected return value. Then go on and read the complete task description below.

The Tennis Kata

Tennis has a rather quirky scoring system, and to newcomers it can be a little difficult to keep track of. The tennis society has contracted you to build a scoreboard to display the current score during tennis games.

Your task is to write a “TennisGame” class containing the logic which outputs the correct score as a string for display on the scoreboard. When a player scores a point, it triggers a method to be called on your class letting you know who scored the point. Later, you will get a call “score()” from the scoreboard asking what it should display. This method should return a string with the current score.

You can read more about Tennis scores at wikipedia which is summarized below:

1. A game is won by the first player to have won at least four points in total and at least two points more than the opponent.
2. The running score of each game is described in a manner peculiar to tennis: scores from zero to four points are described as "love", "15", "30", "40" and "Game" respectively.
3. If both players have won the same number of points but less than three points, the score is described as "love-all", "15-all" and "30-all". If at least three points have been scored by each player, and the scores are equal, the score is "deuce".
4. If at least three points have been scored by each side and a player has one more point than his opponent, the score of the game is "Advantage" for the player in the lead.

You need only report the score for the current game. Sets and Matches are out of scope.

Examples

• If the game has just begun, the score is "love-all".
• If the first player has won one point and second none, the score is "15-love".
• If the first player is named "A" and has won four points and the second player has won three points, the score is "Advantage A".
• If the first player is named "A" and has won five points and the second player has won three points, player "A" has won the game. The score is "Game A".

Acknowledgements

This Kata for TDD is based on the Tennis Kata for refactoring of Emily Bache. She provides this Kata for several programming languages. Here is her blog post and the code is on github.