Go Fish — TDD Class Design

Inspired by the Bowling Game Kata approach: let the tests drive you toward the simplest structure that works. Start with the Game and let Card, Deck, Hand, and Player emerge only when the tests demand them.

Design Philosophy (Kata-Style)

Just like the Bowling Kata resists the temptation to model Frame as a class, resist modeling every Go Fish noun up front. The test sequence below reveals which structs earn their existence.

Structs

Card

Represents a single playing card.

Methods

• String() string — human-readable label, e.g. "A of Spades"
• Equals(other Card) bool — rank equality (suit is irrelevant for matching)

Deck

An ordered collection of cards that can be drawn from.

Methods

• NewDeck() Deck — builds a standard 52-card deck
• Shuffle() — randomizes card order
• Draw() (Card, bool) — removes and returns the top card; bool signals empty deck
• IsEmpty() bool
• Size() int

Hand

The cards held by one player.

Methods

• AddCard(card Card)
• HasRank(rank string) bool
• TakeCardsOfRank(rank string) []Card — removes and returns all matching cards
• CollectBook() int — scans for sets of 4; lays them down and returns how many books were scored
• IsEmpty() bool
• Size() int
• Ranks() []string — distinct ranks currently held (used to validate asks)

Player

Wraps a Hand with identity and a book count.

Methods

• NewPlayer(name string) Player
• Ask(target *Player, rank string) bool — asks target for a rank; returns true if cards were received
• GoFish(deck *Deck) bool — draws one card; returns true if it matched a rank already held
• Books() int — total books scored so far
• Name() string

Game

Orchestrates the full game. This is where the tests drive almost all the logic.

Methods

• NewGame(playerNames []string) Game — creates players, builds and shuffles the deck
• Deal() — distributes opening hand (7 cards for 2 players, 5 cards for 3+)
• CurrentPlayer() *Player
• TakeTurn(targetPlayerName string, rank string) TurnResult — core kata method; executes one complete turn: ask → receive or go fish → collect books → advance turn
• IsOver() bool — true when deck is empty AND at least one player has an empty hand
• Winner() *Player — player with the most books; nil if game is not over
• Scores() map[string]int — snapshot of all players' book counts

TurnResult (value type)

Returned by TakeTurn to keep test assertions readable without inspecting internal state.

Suggested Test Sequence (Kata Order)

Following the kata spirit, write tests in this order so each one forces exactly one new concept:

1. New game has correct number of players → drives NewGame
2. Deal gives each player the right hand size → drives Deal and Hand.Size
3. Ask a player who has the rank — receive cards → drives Ask and Hand.TakeCardsOfRank
4. Ask a player who lacks the rank — Go Fish → drives GoFish and Deck.Draw
5. Four of a kind forms a book → drives Hand.CollectBook
6. Fish card that matches held rank scores a book immediately → drives FishMatched
7. Player who asks successfully goes again → drives TurnResult.TurnChanged
8. Game ends when deck is empty and a hand is empty → drives IsOver
9. Player with most books wins → drives Winner
10. Tie is handled gracefully → hardens Winner

What Deliberately Has No Class