TDD Intro

This repository and its associated video series has everything you need to conduct an introductory workshop on test-driven development. It uses JavaScript and Node.js.

To conduct this workshop with a group, read the facilitation guide here.

To conduct this workshop as a self-study session, start with episode 1 of the video series: letscodejavascript.com/v3/comments/tdd_intro/1. It will walk you through everything you need.

Prerequisites

You need the following programs to use this repository:

• Git
• Node.js

Branches

The following branches are available in this repository:

• facilitator: Facilitator guide and materials (in the facilitator directory).
• start_here: The starting point for the example exercise in the video series.
• continue_here: Where the video series ends and the viewer is prompted to continue on there own.
• completed: The finished program.

Running the Program

The program is a simple scoring tool for the Cribbage card game. It's run from the command-line, like this:

$ ./run.sh JH5D5S5C5H
29

On Windows, use run instead of ./run.sh.

That command means "score a hand consisting of Jack of Hearts, 5 of Diamonds, 5 of Spades, and 5 of Clubs, with the 5 of Hearts as the starter card." (This happens to be the highest-scoring hand in Cribbage.) Each card is represented by a pair of characters.

1. The first character is the rank of the card, with '0' representing '10': A, 2, 3, 4, 5, 6, 7, 8, 9, 0, J, Q, K.
2. The second character is the suit of the card: H, S, D, C referring to Hearts, Spades, Diamonds, and Clubs respectively.

Depending on which branch of the repository you check out, the program be partially implemented as an exercise for you to complete. See the facilitator branch for more details.

Here are all the commands that are available:

• ./run.sh (run on Windows): Run the program.
• ./build.sh (build on Windows): Run the build script, which will automatically lint the code and run its tests.
• ./watch.sh quick (watch quick on Windows): Run the build script on files that have changed, and re-run it every time a file changes. On MacOS, it will also play a sound indicating build success or failure.
• ./clean.sh (clean on Windows): Delete files created by the build.

Writing the Program

For details about writing the program, see the the facilitator branch. Here are the main facts:

• The program is written in JavaScript and uses Node.js.
• The test framework is Mocha.
• The assertion library is Chai.
• Source code is in the src/ folder. Command-line infrastructure, including the entry point to the program, is in src/cli/.
• The main module is src/score.js. The command-line infrastructure calls analyze() in that module. It provides analyze() with a string representing the first command-line parameter (or undefined if there wasn't one) and then prints whatever analyze() returns.
• Tests are run from the src/ folder. They must start with an underscore and end with _test, like this: src/_score_test.js.
• Build infrastructure is in the build/ folder. You can ignore it.

Cribbage Scoring Rules

Cribbage scoring is based on a hand of four cards plus a "starter" card. The score is calculated by finding all combinations of cards that meet the following criteria:

• Pair of cards: 2 points
• Straight of three cards or more: 1 point per card
  • Aces are low, so A, 2, 3 is a valid straight, but Q, K, A is not.
• 4-card flush excluding starter card: 4 points
• 5-card flush including starter card: 5 points
• Jack in the hand whose suit matches the starter card's suit: 1 point
• Card values that add up to 15: 2 points
  • Aces' values are 1.
  • Jacks, Queens, and Kings' values are 10.
  • All other cards' values are equal to their numbers.
  • Example: King + Ace + 4 = 10 + 1 + 4 = 15.

Every unique combination of cards can be used. For example, a hand consisting of 7 of Hearts, 8 of Spades, 8 of Hearts, 8 of Diamonds, with a starter card of 9 of Clubs can be scored as follows:

• 8 of Spades + 8 of Hearts: pair (2 points)
• 8 of Spades + 8 of Diamonds: pair (2 points)
• 8 of Hearts + 8 of Diamonds: pair (2 points)
• 7 of Hearts + 8 of Spades + 9 of Clubs: straight (3 points)
• 7 of Hearts + 8 of Hearts + 9 of Clubs: straight (3 points)
• 7 of Hearts + 8 of Diamonds + 9 of Clubs: straight (3 points)
• 7 of Hearts + 8 of Spades: adds up to 15 (2 points)
• 7 of Hearts + 8 of Hearts: adds up to 15 (2 points)
• 7 of Hearts + 8 of Diamonds: adds up to 15 (2 points)

Total score: 21 (A very good hand!)

However, subsets of straights and flushes may only be counted once. In other words, a four-card straight is only worth three points; it doesn't get counted as a three-card straight and a four-card straight. Same for flushes. For example, a hand consisting of 2, 3, 4, and 5 of Hearts, with a starter card of 6 of Hearts, would be scored as follows:

• 2, 3, 4, 5, 6 of Hearts: straight (5 points)
• 2, 3, 4, 5, 6 of Hearts: flush (5 points)
• 2, 3, 4, 6 of Hearts: adds up to 15 (2 points)
• 4, 5, 6 of Hearts: adds up to 15 (2 points)

Total score: 14 (A good score, but not as amazing as you might expect from a straight flush.)