Bowling Game
Level: Advanced 60–90 minConcepts: Edge CasesState
Solutions: C# | TypeScript | Python
Create a program to score a game of ten-pin bowling.
Requirements
- Calculate the score for a game of ten-pin bowling
- Handle all valid bowling scenarios:
- Regular frames (sum of pins knocked down)
- Spares (10 pins in two rolls, bonus is next roll)
- Strikes (10 pins in one roll, bonus is next two rolls)
- 10th frame special cases (up to three rolls)
- Validate input:
- Number of pins must be between 0 and 10
- Sum of pins in a frame (except last) must not exceed 10
- Proper number of rolls based on game progress
Test Cases
| Scenario | Rolls | Score | Notes |
|---|---|---|---|
| All Gutter Balls | 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 | 0 | No pins knocked down |
| All Ones | 1,1, 1,1, 1,1, 1,1, 1,1, 1,1, 1,1, 1,1, 1,1, 1,1 | 20 | One pin per roll |
| One Spare | 5,5, 3,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 | 16 | Spare + bonus |
| One Strike | 10, 3,4, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0, 0,0 | 24 | Strike + bonus |
| Perfect Game | 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,10,10 | 300 | All strikes |
| All Spares | 5,5, 5,5, 5,5, 5,5, 5,5, 5,5, 5,5, 5,5, 5,5, 5,5, 5,5,5 | 150 | All spares |
Edge Cases to Consider
- Invalid number of pins (>10 or <0)
- Invalid frame totals (>10 in a frame)
- Wrong number of rolls for the game state
- Invalid bonus rolls in 10th frame
- Empty or null input
Tips
- Start with the simplest case (all zeros)
- Add support for regular frames first
- Then add spares, then strikes
- Handle the 10th frame as a special case
- Consider using a Frame class to encapsulate frame logic
Reference Walkthrough
Full C#, TypeScript, and Python implementations live at tddbuddy-reference-katas/bowling-game — the same six scenarios across all three languages, walked commit-by-commit through the TDD cycle.
- C# (.NET 8, xUnit, FluentAssertions) — walkthrough
- TypeScript (Node 20, Vitest, strict types) — walkthrough
- Python (3.11, pytest) — walkthrough
This is a Pedagogy mode kata — the walkthroughs step through the TDD cycle commit-by-commit. Watch the gear shift from low (fake-it, sum) to middle once the scoring loop’s two-mode index (frame vs roll cursor) lands. The teaching point is the class that does not get written: two reflect — commits mark the moments the author was tempted to extract a Frame type and chose not to — the Frame concept lives in the rollIndex += 1 vs rollIndex += 2 advance, not in a class. See the repo’s Gears section for why resisting a premature abstraction is itself a TDD skill.
Related reading
- Examples Pin Intent. Properties Pin the Invariants.
Example-based tests anchor scenarios in the team's vocabulary. Property-based tests anchor invariants across the input space. The agent needs both axes, and most suites only carry one. - Test Deletion Is a Privileged Operation
The cheapest way for an agent to make a failing test pass is to delete it. That is logical for the agent and catastrophic for the codebase. Tests are append-only by default. Deletion needs a human author, a separate commit, and a separate review. - The Instruction File Is Not the Discipline
Teams that want their agent to do TDD reach for the instruction file. The TDAD paper measured this directly: adding a 'do TDD' instruction raised regressions by nearly two-thirds. Contextual test discovery cut them by seventy percent. The instruction is theatre. The codebase's test surface is the discipline.