Resolve pending commit links for MIL-004 acceptance

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitignore

@@ -174,3 +174,6 @@ cython_debug/
 # PyPI configuration file
 .pypirc
 
+
+# Doxygen output
+docs/doxygen/

README.md

@@ -1,2 +1,100 @@
-# 014-higher_lower
+# Higher Lower
 
+A console game from Udemy's *100 Days of Code: The Complete Python Pro Bootcamp*
+(day 14). Two Instagram accounts are shown. Guess which one has more followers.
+Every right guess adds a point and the winner stays for the next round. A wrong
+guess ends the game.
+
+```
+Compare A: Cristiano Ronaldo, a Footballer, from Portugal.
+
+ _    __
+| |  / /____
+| | / / ___/
+| |/ (__  )
+|___/____(_)
+
+Against B: Ariana Grande, a Musician and actress, from United States.
+Who has more followers? Type 'A' or 'B':
+```
+
+- Python 3.13 or newer, no runtime dependencies.
+- The function names follow the assignment: `format_data`, `check_answer`.
+- Each account is shown once per game; if you get through all 50, you win.
+- Follower counts are in millions and come from the assignment's data set.
+
+## Requirements
+
+- [Python](https://www.python.org/downloads/) 3.13 or newer
+- Optional: [Doxygen](https://www.doxygen.nl/) to build the source documentation
+
+## Set up
+
+Create a local virtual environment in `.venv`, activate it, and upgrade `pip`.
+
+Windows (PowerShell):
+
+```powershell
+python -m venv .venv
+.venv\Scripts\Activate.ps1
+python -m pip install --upgrade pip
+```
+
+Windows (Git Bash), Linux and macOS:
+
+```bash
+python -m venv .venv
+source .venv/Scripts/activate   # Linux/macOS: source .venv/bin/activate
+python -m pip install --upgrade pip
+```
+
+The game itself needs nothing more. To run the tests and the code checks, install the
+development tools:
+
+```bash
+python -m pip install -e ".[dev]"
+```
+
+## Run the game
+
+```bash
+python -m higher_lower
+```
+
+Type `A` or `B` and press Enter. Press Ctrl+C to quit.
+
+## Run the tests
+
+```bash
+python -m pytest
+```
+
+Check the code style and types:
+
+```bash
+python -m ruff check src tests
+python -m ruff format --check src tests
+python -m mypy src tests
+```
+
+## Build the source documentation
+
+The source uses Doxygen comments. The HTML output goes to `docs/doxygen/html`.
+
+```bash
+doxygen Doxyfile
+```
+
+## Project layout
+
+| Path | Content |
+| --- | --- |
+| `src/higher_lower/` | The game: `game_logic.py` (pure functions), `game.py` (the loop), `game_data.py`, `art.py`, `constants.py` |
+| `tests/` | pytest tests |
+| `docs/` | Planning and review documents (business case, plan, milestones, use case) |
+| `pyproject.toml` | Project configuration |
+| `Doxyfile` | Doxygen configuration |
+
+## License
+
+GNU Affero General Public License v3.0. See [LICENSE](LICENSE).

docs/artifact-registry.md

@@ -15,8 +15,12 @@ document of a type. `Primary File` may contain a glob (e.g.
 | SA | Stakeholder Analysis | docs/stakeholder-analysis.md | 002 |
 | PP | Project Plan | docs/project-plan.md | 002 |
 | MIL | Milestone / Gateway | docs/milestones/*.md | 005 |
-| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 005 |
+| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 013 |
 | TM | Traceability Matrix | docs/sqa/traceability-matrix.md | 002 |
+| UCD | Use Case Diagram | docs/use-case-diagram.md | 002 |
+| US | User Story | docs/user-stories.md | 002 |
+| UC | Use Case | docs/uc-*/uc.md | 002 |
+| SSD | System Sequence Diagram | docs/uc-*/ssd.md | 002 |
 
 ## Languages
 

docs/milestones/mil-002-game-logic.md

@@ -4,12 +4,13 @@
 | Key | Value |
 | --- | --- |
 | ID | MIL-002 |
-| CrossReference | [BC-001], [PP-001] |
+| CrossReference | [BC-001], [PP-001], [RC-005] |
 
 ## Version History
 | Date | Status | Author | Reviewer | Change | Commit |
 | --- | --- | --- | --- | --- | --- |
-| 2026-10-04 | Proposed | Jens Tirsvad Nielsen | S01 | Initial version | [ddfe96f] |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [ddfe96f] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Accepted after review RC-005 | [ee58fcd] |
 
 ---
 
@@ -72,3 +73,5 @@ The assignment data set and art as modules, constants in `constants.py`, and the
 [PP-001]: ../project-plan.md
 [MIL-001]: ./mil-001-project-setup.md
 [ddfe96f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/ddfe96ffa459d5e4b2e30d71bd53878aba2cfc5d
+[RC-005]: ../sqa/reviews/rc-005-mil-002.md
+[ee58fcd]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/ee58fcdc1c9c83b0721022d623e4989591a47987

docs/milestones/mil-003-console-game.md

@@ -4,12 +4,13 @@
 | Key | Value |
 | --- | --- |
 | ID | MIL-003 |
-| CrossReference | [BC-001], [PP-001] |
+| CrossReference | [BC-001], [PP-001], [US-001], [RC-006] |
 
 ## Version History
 | Date | Status | Author | Reviewer | Change | Commit |
 | --- | --- | --- | --- | --- | --- |
-| 2026-10-04 | Proposed | Jens Tirsvad Nielsen | S01 | Initial version | [ddfe96f] |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [ddfe96f] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Linked UC-001 and the user stories<br>Accepted after review RC-006 | [923dde7] |
 
 ---
 
@@ -43,6 +44,7 @@ An interactive console game started with `python -m higher_lower`, built on the
 | Business Case objective / KPI / user story | Reference |
 | --- | --- |
 | O1, O3 | [BC-001] |
+| US-001.01, US-001.02 | [US-001] |
 
 ## Ownership
 
@@ -60,7 +62,7 @@ An interactive console game started with `python -m higher_lower`, built on the
 | # | Task | Summary | Needs its own Use Case/User Story? | Reference |
 | --- | --- | --- | --- | --- |
 | 1 | Implement display and input helpers | A function that prints the logo, "Compare A: ...", the `vs` art and "Against B: ..." using `format_data`, and one that asks for "A" or "B" and re-asks until valid (case-insensitive). Input and output go through injectable callables so tests need no real console. | No | |
-| 2 | Implement the game loop | `play_game()` keeps the score, starts with a random pair, compares guesses with `check_answer`, moves B to A after a correct guess and picks a new B that differs from A. Prints the score after each round and "Sorry, that's wrong. Final score" at the end. | Yes | UC-001 Play a game (to be created with the SSD before this task starts) |
+| 2 | Implement the game loop | `play_game()` keeps the score, starts with a random pair, compares guesses with `check_answer`, moves B to A after a correct guess and picks a new B that differs from A. Prints the score after each round and "Sorry, that's wrong. Final score" at the end. | Yes | [UC-001], [US-001] |
 | 3 | Handle exhausted data | If every account has been used, end the game with a win message instead of failing to find a new B. | No | |
 | 4 | Add entry point | `python -m higher_lower` runs `main()`, which calls `play_game()`; no side effects on import. | No | |
 | 5 | Write game loop tests | pytest tests with scripted input and a seeded random generator: correct streak, wrong first guess, invalid input then valid, data exhausted, and the score printed. | No | |
@@ -71,3 +73,7 @@ An interactive console game started with `python -m higher_lower`, built on the
 [PP-001]: ../project-plan.md
 [MIL-002]: ./mil-002-game-logic.md
 [ddfe96f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/ddfe96ffa459d5e4b2e30d71bd53878aba2cfc5d
+[US-001]: ../user-stories.md
+[UC-001]: ../uc-001/uc.md
+[RC-006]: ../sqa/reviews/rc-006-mil-003.md
+[923dde7]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/923dde7dc9b59d2c77eddc88336451193147c557

docs/milestones/mil-004-docs-release.md

@@ -4,12 +4,13 @@
 | Key | Value |
 | --- | --- |
 | ID | MIL-004 |
-| CrossReference | [BC-001], [PP-001] |
+| CrossReference | [BC-001], [PP-001], [RC-011] |
 
 ## Version History
 | Date | Status | Author | Reviewer | Change | Commit |
 | --- | --- | --- | --- | --- | --- |
-| 2026-10-04 | Proposed | Jens Tirsvad Nielsen | S01 | Initial version | [ddfe96f] |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [ddfe96f] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Accepted after review RC-011 | [267e34f] |
 
 ---
 
@@ -70,3 +71,5 @@ Decide whether the repository is ready to be shared with S02 and S03: documented
 [PP-001]: ../project-plan.md
 [MIL-003]: ./mil-003-console-game.md
 [ddfe96f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/ddfe96ffa459d5e4b2e30d71bd53878aba2cfc5d
+[RC-011]: ../sqa/reviews/rc-011-mil-004.md
+[267e34f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/267e34fc9f1fb9d76cc20032f3b09dc8e9dd82c7

docs/sqa/reviews/rc-005-mil-002.md

@@ -0,0 +1,46 @@
+# SQA Review Record: MIL-002 Game logic
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-005 |
+| CrossReference | [MIL-002], [QC-MIL-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [ee58fcd] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-002]
+- Checklist used: [QC-MIL-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | A concrete deliverable is defined for every gate | Pass | Data and art modules, constants, four named functions, Doxygen comments, pytest tests. |
+| 2 | Explicit Go/No-Go criteria are stated for each gate | Pass | Six objectively checkable criteria. |
+| 3 | Dependencies on other milestones are explicitly mapped (Optional) | Pass | Depends on MIL-001, with the reason. |
+| 4 | Each milestone is traceable to a Business Case objective or KPI | Pass | O1, O2, O3. |
+| 5 | Milestone owner and approving reviewer are identified | Pass | S01 and S01. |
+| 6 | Milestone has a target date consistent with project constraints | Pass | 2026-10-09, inside the 2026-10-14 constraint in BC-001. |
+
+## Overall Verdict
+
+Go — all criteria pass. Code under `src/` and `tests/` for MIL-002 may start once the MIL-001 deliverables exist (its dependency). MIL-003 and MIL-004 stay Proposed. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| Deliver MIL-001 (issues #1-#4) before starting MIL-002 tasks | S01 | 2026-10-06 |
+
+---
+
+[MIL-002]: ../../milestones/mil-002-game-logic.md
+[QC-MIL-001]: ../../../framework/qc/qc-milestones-gateways.md
+[ee58fcd]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/ee58fcdc1c9c83b0721022d623e4989591a47987

docs/sqa/reviews/rc-006-mil-003.md

@@ -0,0 +1,47 @@
+# SQA Review Record: MIL-003 Console game
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-006 |
+| CrossReference | [MIL-003], [QC-MIL-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [923dde7] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-003]
+- Checklist used: [QC-MIL-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | A concrete deliverable is defined for every gate | Pass | A playable console game started with python -m higher_lower, with loop tests. |
+| 2 | Explicit Go/No-Go criteria are stated for each gate | Pass | Six objectively checkable criteria. |
+| 3 | Dependencies on other milestones are explicitly mapped (Optional) | Pass | Depends on MIL-002, with the reason. |
+| 4 | Each milestone is traceable to a Business Case objective or KPI | Pass | O1, O3; stories US-001.01 and US-001.02. |
+| 5 | Milestone owner and approving reviewer are identified | Pass | S01 and S01. |
+| 6 | Milestone has a target date consistent with project constraints | Pass | 2026-10-12, inside the 2026-10-14 constraint in BC-001. |
+
+## Overall Verdict
+
+Go — all criteria pass. UC-001 and its SSD were created for task 2 (the game loop); UCD-001, US-001, UC-001 and SSD-001 stay Proposed until they are reviewed. MIL-004 stays Proposed. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| Review UCD-001, US-001, UC-001 and SSD-001 against their QC checklists | S01 | 2026-10-12 |
+| Add UCD-001 and US-001 to the CrossReference of BC-001 and PP-001 when those documents are next edited | S01 | 2026-10-14 |
+
+---
+
+[MIL-003]: ../../milestones/mil-003-console-game.md
+[QC-MIL-001]: ../../../framework/qc/qc-milestones-gateways.md
+[923dde7]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/923dde7dc9b59d2c77eddc88336451193147c557

docs/sqa/reviews/rc-007-ucd-001.md

@@ -0,0 +1,48 @@
+# SQA Review Record: UCD-001 Use Case Diagram
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-007 |
+| CrossReference | [UCD-001], [QC-UCD-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [c7164fe] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [UCD-001]
+- Checklist used: [QC-UCD-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Actors are defined with correct UML stereotypes (e.g. `<<System>>`, `<<Actor>>`) | Pass | Actor <<Actor>> and boundary <<System>> stereotyped. |
+| 2 | System boundary is clearly drawn and labeled | Pass | Boundary rectangle labelled Higher Lower. |
+| 3 | Include/extend relationships are used correctly per UML 2.5.1, not as generic "uses" arrows | Pass | No include/extend used; the Relationships section says so. |
+| 4 | Every actor participates in at least one use case (no orphan actors) | Pass | Player is in Play a Game. |
+| 5 | Diagram is traceable to a documented stakeholder need | Pass | Player traces to S01 and S02 in SA-001. |
+| 6 | Use case names are verb phrases describing actor goals, not internal system operations | Pass | Play a Game is an actor goal. |
+| 7 | Diagram is free of implementation detail (e.g. UI widgets, database tables) (Optional) | Pass | No UI or storage detail. |
+| 8 | Actor and use case naming is consistent with corresponding Use Case and User Story documents (Optional) | Pass | Names match US-001 and UC-001. |
+
+## Overall Verdict
+
+Go — all applicable criteria pass. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | — | — |
+
+---
+
+[UCD-001]: ../../use-case-diagram.md
+[QC-UCD-001]: ../../../framework/qc/qc-use-case-diagram.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/sqa/reviews/rc-008-us-001.md

@@ -0,0 +1,47 @@
+# SQA Review Record: US-001 User Stories
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-008 |
+| CrossReference | [US-001], [QC-US-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [c7164fe] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [US-001]
+- Checklist used: [QC-US-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Follows INVEST criteria (Independent, Negotiable, Valuable, Estimable, Small, Testable) | Pass | INVEST check present, no exceptions. |
+| 2 | Written in "As a / I want / So that" form | Pass | Both stories use As a / I want / so that. |
+| 3 | Clear, testable acceptance criteria are included | Pass | Given/When/Then criteria on both stories. |
+| 4 | Traceable to a use case or epic | Pass | Both trace to UC-001 and MIL-003. |
+| 5 | Story is sized to fit within a single iteration (Optional) | Pass | Each fits one iteration. |
+| 6 | Story statement avoids technical implementation detail (Optional) | Pass | Stated as player goals. |
+| 7 | Role named in the story matches an actor defined in the Use Case Diagram | Pass | Role Player matches UCD-001. |
+
+## Overall Verdict
+
+Go — all applicable criteria pass. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | — | — |
+
+---
+
+[US-001]: ../../user-stories.md
+[QC-US-001]: ../../../framework/qc/qc-user-story.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/sqa/reviews/rc-009-uc-001.md

@@ -0,0 +1,52 @@
+# SQA Review Record: UC-001 Use Case
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-009 |
+| CrossReference | [UC-001], [QC-UC-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [c7164fe] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [UC-001]
+- Checklist used: [QC-UC-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Consists of a single, concise paragraph summarizing only the primary success scenario | N-A | Applies to the Brief format only; this use case is Fully Dressed. |
+| 2 | Written as an informal multi-paragraph narrative; may mention some alternate flows without formal structure | N-A | Applies to the Casual format only; this use case is Fully Dressed. |
+| 3 | All standard sections are present: actors, preconditions, postconditions, main success scenario, alternative/exception flows | Pass | Scope, level, actor, stakeholders, pre/postconditions, scenario, extensions, rules and open issues present. |
+| 4 | Preconditions and postconditions are explicitly defined | Pass | Both defined. |
+| 5 | Primary actor is explicitly stated | Pass | Player. |
+| 6 | Stakeholders and their interests are stated | Pass | S01 and S02 with interests. |
+| 7 | Main success scenario is written as clear, numbered steps | Pass | Seven numbered steps. |
+| 8 | Alternative/exception flows correctly reference `<<include>>`/`<<extend>>` use cases where relevant, per UML 2.5.1 | Pass | No include/extend applies; stated. |
+| 9 | Explicit business rules are captured per step where applicable, rather than embedded loosely in narrative text (Optional) | Pass | Rules listed for steps 2, 3b and 5. |
+| 10 | Naming of actors and use case title is consistent with the corresponding Use Case Diagram and User Stories | Pass | Title and actor match UCD-001 and US-001. |
+| 11 | Scope/level (e.g. summary, user-goal, subfunction) is explicitly stated (Optional) | Pass | Level: user goal. |
+| 12 | Use case is written from the actor's goal perspective, free of UI or implementation detail | Pass | Goal wording, no UI or implementation detail. |
+
+## Overall Verdict
+
+Go — all applicable criteria pass. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | — | — |
+
+---
+
+[UC-001]: ../../uc-001/uc.md
+[QC-UC-001]: ../../../framework/qc/qc-use-case.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/sqa/reviews/rc-010-ssd-001.md

@@ -0,0 +1,47 @@
+# SQA Review Record: SSD-001 System Sequence Diagram
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-010 |
+| CrossReference | [SSD-001], [QC-SSD-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [c7164fe] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [SSD-001]
+- Checklist used: [QC-SSD-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Input/output messages match the corresponding Use Case's main success scenario step-for-step | Pass | startGame and makeGuess cover steps 1 to 7 of UC-001. |
+| 2 | Actor and System are treated strictly as black boxes (system shown as `:System`) | Pass | Only Player and :System. |
+| 3 | Object creation/destruction of the System instance handled explicitly where relevant (Optional) | Pass | Lifecycle notes state when the game starts and ends. |
+| 4 | Return values are shown for operations that produce one, using dashed return arrows | Pass | Dashed returns on every operation. |
+| 5 | Alternate/exceptional flows are represented separately (or explicitly out of scope noted) | Pass | Alternative flows noted as out of scope. |
+| 6 | Message names are verb phrases consistent with the use case's system responsibilities (Optional) | Pass | startGame, makeGuess. |
+| 7 | Diagram references the specific Use Case (name and ID) it depicts | Pass | Cites UC-001 Play a Game. |
+
+## Overall Verdict
+
+Go — all applicable criteria pass. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | — | — |
+
+---
+
+[SSD-001]: ../../uc-001/ssd.md
+[QC-SSD-001]: ../../../framework/qc/qc-ssd.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/sqa/reviews/rc-011-mil-004.md

@@ -0,0 +1,46 @@
+# SQA Review Record: MIL-004 Documentation and release
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-011 |
+| CrossReference | [MIL-004], [QC-MIL-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [267e34f] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-004]
+- Checklist used: [QC-MIL-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | A concrete deliverable is defined for every gate | Pass | README, Doxygen build, review records and a verified clean copy. |
+| 2 | Explicit Go/No-Go criteria are stated for each gate | Pass | Six objectively checkable criteria. |
+| 3 | Dependencies on other milestones are explicitly mapped (Optional) | Pass | Depends on MIL-003, with the reason. |
+| 4 | Each milestone is traceable to a Business Case objective or KPI | Pass | O2, O4, O5. |
+| 5 | Milestone owner and approving reviewer are identified | Pass | S01 and S01. |
+| 6 | Milestone has a target date consistent with project constraints | Pass | 2026-10-14, the date in the BC-001 constraint. |
+
+## Overall Verdict
+
+Go — all criteria pass. Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | — | — |
+
+---
+
+[MIL-004]: ../../milestones/mil-004-docs-release.md
+[QC-MIL-001]: ../../../framework/qc/qc-milestones-gateways.md
+[267e34f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/267e34fc9f1fb9d76cc20032f3b09dc8e9dd82c7

docs/sqa/reviews/rc-012-source-code.md

@@ -0,0 +1,52 @@
+# SQA Review Record: Source code of higher_lower
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-012 |
+| CrossReference | [QC-PY-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Initial version | [267e34f] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: the Python source in `src/higher_lower/` and `tests/` at the commit of this review (source code has no artifact ID)
+- Checklist used: [QC-PY-001]
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | Modules and functions snake_case, constants UPPER_SNAKE, TypedDict PascalCase; ruff (E, F, I, UP, FLY, B) passes. |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names say purpose (check_answer, pick_pair); i/n-style names are not used. |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | `ruff check` and `ruff format --check` pass; the only suppression is E501 for the verbatim data file, with a comment in pyproject.toml. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | All signatures annotated; `mypy --strict src tests` reports no issues. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | No bare except; `main` catches EOFError and KeyboardInterrupt on purpose and leaves with a goodbye. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults; the data list default is a read-only module constant. |
+| 7 | Files, locks and connections are managed with context managers | N-A | The code opens no files, locks or connections. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how (Optional) | Pass | Every module, class and function has a Doxygen docstring; checked with an AST script. |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | N-A | The game prints its interface to the console; there is no logging, and no secrets or personal data are printed. |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | N-A | No Design Class Diagram exists or is planned; the only class is the Account TypedDict, and the functions implement the operations of SSD-001. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | 36 pytest tests named for behaviour, with scripted input and seeded randomness; no network, no order dependence. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment (Optional) | Pass | mypy strict runs without errors; no Any is used. |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused (Optional) | Pass | No runtime dependencies; dev tools declared in pyproject.toml with version ranges. |
+
+## Overall Verdict
+
+Go — all applicable criteria pass. The review found a lint ordering error, format differences and strict-typing errors; they were fixed before this verdict (ruff import order and format, `Final` on the account key constants). Reviewer and author are both S01: the project has a single participant, so the framework's author/reviewer separation cannot be met. S01 accepted this deviation when requesting acceptance (2026-10-04).
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | — | — |
+
+---
+
+[QC-PY-001]: ../../../framework/qc/qc-programming-python.md
+[267e34f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/267e34fc9f1fb9d76cc20032f3b09dc8e9dd82c7

docs/sqa/traceability-matrix.md

@@ -9,7 +9,8 @@
 ## Version History
 | Date | Status | Author | Reviewer | Change | Commit |
 | --- | --- | --- | --- | --- | --- |
-| 2026-10-04 | Proposed | Jens Tirsvad Nielsen | S01 | Initial version | [a1ff735] |
+| 2026-10-04 | Proposed | Jens Tirsvad Nielsen | S01 | Added RC-007 to RC-010 for UCD-001, US-001, UC-001 and SSD-001 | [c7164fe] |
+| 2026-10-04 | Proposed | Jens Tirsvad Nielsen | S01 | Added RC-011 and RC-012 | [267e34f] |
 
 ---
 
@@ -26,13 +27,18 @@ target is measurable. A row is added or updated whenever an artifact instance is
 | [SA-001] | SA | [BC-001] | [PP-001] | [RC-002] |
 | [PP-001] | PP | [BC-001], [SA-001] | [MIL-001], [MIL-002], [MIL-003], [MIL-004] | [RC-003] |
 | [MIL-001] | MIL | [BC-001], [PP-001] | - | [RC-004] |
-| [MIL-002] | MIL | [BC-001], [PP-001] | - | - |
+| [MIL-002] | MIL | [BC-001], [PP-001], [MIL-001] | - | [RC-005] |
-| [MIL-003] | MIL | [BC-001], [PP-001] | - | - |
+| [MIL-003] | MIL | [BC-001], [PP-001], [MIL-002], [US-001] | [MIL-004], [UC-001] | [RC-006] |
-| [MIL-004] | MIL | [BC-001], [PP-001] | - | - |
+| [MIL-004] | MIL | [BC-001], [PP-001], [MIL-003] | - | [RC-011] |
+| [UCD-001] | UCD | [SA-001], [BC-001] | [US-001], [UC-001] | [RC-007] |
+| [US-001] | US | [UCD-001], [BC-001], [MIL-003] | [UC-001] | [RC-008] |
+| [UC-001] | UC | [UCD-001], [US-001], [SA-001] | [SSD-001] | [RC-009] |
+| [SSD-001] | SSD | [UC-001] | - | [RC-010] |
 
 ## Coverage Notes
 
-- No use cases, user stories or design artifacts exist yet (UC-001 is planned for MIL-003).
+- No domain model or design artifacts exist yet.
+- RC-012 reviews the Python source against QC-PY-001; source code has no artifact ID, so it has no row above.
 - `-` in Upstream means foundational; in Downstream, nothing is built on it yet; in Last Reviewed, no `RC-*` exists yet.
 
 ---
@@ -48,4 +54,17 @@ target is measurable. A row is added or updated whenever an artifact instance is
 [RC-002]: ./reviews/rc-002-stakeholder-analysis.md
 [RC-003]: ./reviews/rc-003-project-plan.md
 [RC-004]: ./reviews/rc-004-mil-001.md
-[a1ff735]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/a1ff73580fdcfad5bbb3854298fdfa0c16ada853
+[RC-005]: ./reviews/rc-005-mil-002.md
+[UCD-001]: ../use-case-diagram.md
+[US-001]: ../user-stories.md
+[UC-001]: ../uc-001/uc.md
+[SSD-001]: ../uc-001/ssd.md
+[RC-006]: ./reviews/rc-006-mil-003.md
+[RC-007]: ./reviews/rc-007-ucd-001.md
+[RC-008]: ./reviews/rc-008-us-001.md
+[RC-009]: ./reviews/rc-009-uc-001.md
+[RC-010]: ./reviews/rc-010-ssd-001.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0
+[RC-011]: ./reviews/rc-011-mil-004.md
+[RC-012]: ./reviews/rc-012-source-code.md
+[267e34f]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/267e34fc9f1fb9d76cc20032f3b09dc8e9dd82c7

docs/uc-001/ssd.md

@@ -0,0 +1,57 @@
+# System Sequence Diagram: Play a Game
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | SSD-001 |
+| CrossReference | [UC-001], [RC-010] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [923dde7] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Accepted after review RC-010 | [c7164fe] |
+
+---
+
+## Source Use Case
+
+[UC-001] Play a Game, main success scenario. The alternative flows (invalid answer, tie, no account left) are out of scope for this diagram.
+
+## Diagram
+
+```plantuml
+@startuml
+actor Player
+participant ":System" as System
+Player -> System : startGame()
+System --> Player : accounts A and B
+loop while the guess is right
+  Player -> System : makeGuess(choice)
+  System --> Player : right, score, new accounts A and B
+end
+Player -> System : makeGuess(choice)
+System --> Player : wrong, final score
+@enduml
+```
+
+## System Operations Table
+
+| Step | Message (verb phrase) | Parameters | Return | Use case step |
+| --- | --- | --- | --- | --- |
+| 1 | startGame | none | accounts A and B | 1, 2 |
+| 2 | makeGuess | choice (A or B) | right, new score, new accounts A and B | 3, 4, 5, 6 |
+| 3 | makeGuess | choice (A or B) | wrong, final score | 3, 7 |
+
+Steps 2 and 3 are the same operation; the loop shows the right-guess outcome repeating, and the last call shows the wrong-guess outcome.
+
+## Lifecycle Notes
+
+A game starts with `startGame` and ends when `makeGuess` returns wrong; the System keeps the score and the current accounts in between.
+
+---
+
+[UC-001]: ./uc.md
+[923dde7]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/923dde7dc9b59d2c77eddc88336451193147c557
+[RC-010]: ../sqa/reviews/rc-010-ssd-001.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/uc-001/uc.md

@@ -0,0 +1,81 @@
+# UC-001 Play a Game
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | UC-001 |
+| CrossReference | [UCD-001], [US-001], [SA-001], [SSD-001], [RC-009] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [923dde7] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Accepted after review RC-009 | [c7164fe] |
+
+---
+
+Format: Fully Dressed
+
+## Scope
+
+The Higher Lower console game.
+
+## Level
+
+User goal.
+
+## Primary Actor
+
+Player.
+
+## Stakeholders and Interests
+
+| Stakeholder | Interest |
+| --- | --- |
+| S01 | A correct game that shows good practice ([SA-001]) |
+| S02 | Readable behaviour that matches the assignment ([SA-001]) |
+
+## Preconditions
+
+The Player has started the game.
+
+## Postconditions (Success Guarantee)
+
+The Player has seen the final score of the game.
+
+## Main Success Scenario
+
+1. The Player starts a game.
+2. The System shows two different accounts, A and B.
+3. The Player guesses which account has more followers.
+4. The System tells the Player the guess was right, adds one to the score, and shows the new score.
+5. The System makes the account the Player compared against the new A and shows a new B.
+6. The Player repeats from step 3 until a guess is wrong.
+7. The System tells the Player the guess was wrong and shows the final score.
+
+## Extensions / Alternative Flows
+
+- 3a. The Player gives an answer that is not a valid choice: the System asks again; the round does not change.
+- 3b. Both accounts have the same number of followers: either choice counts as right.
+- 5a. No account is left that differs from the current A: the System ends the game and shows the final score.
+
+No `<<include>>` or `<<extend>>` use cases apply.
+
+## Special Requirements / Business Rules
+
+- Step 2 and 5: A and B are never the same account.
+- Step 3b: equal follower counts make both choices right.
+
+## Open Issues
+
+None.
+
+---
+
+[UCD-001]: ../use-case-diagram.md
+[US-001]: ../user-stories.md
+[SA-001]: ../stakeholder-analysis.md
+[SSD-001]: ./ssd.md
+[923dde7]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/923dde7dc9b59d2c77eddc88336451193147c557
+[RC-009]: ../sqa/reviews/rc-009-uc-001.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/use-case-diagram.md

@@ -0,0 +1,58 @@
+# Use Case Diagram
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | UCD-001 |
+| CrossReference | [SA-001], [BC-001], [US-001], [UC-001], [RC-007] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [923dde7] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Accepted after review RC-007 | [c7164fe] |
+
+---
+
+## Purpose and Scope
+
+The system boundary is the Higher Lower console game. One actor, the Player, uses it to play a game. Traces to [BC-001] objective O1 and to stakeholders S01 and S02 ([SA-001]), who play the game; S03 only reads the repository.
+
+## Diagram
+
+```plantuml
+@startuml
+left to right direction
+actor Player <<Actor>>
+rectangle "Higher Lower <<System>>" {
+  usecase "Play a Game" as PlayAGame
+}
+Player --> PlayAGame
+@enduml
+```
+
+## Actor Table
+
+| Actor | Stereotype | Stakeholder ID (SA) | Goals (use cases) |
+| --- | --- | --- | --- |
+| Player | Actor | S01, S02 | Play a Game |
+
+## Use Case Table
+
+| Use Case | Actor(s) | Goal |
+| --- | --- | --- |
+| Play a Game ([UC-001]) | Player | Guess, round after round, which of two accounts has more followers, and see the final score |
+
+## Relationships
+
+None: there is a single use case, so no `<<include>>` or `<<extend>>` is used.
+
+---
+
+[SA-001]: ./stakeholder-analysis.md
+[BC-001]: ./business-case.md
+[US-001]: ./user-stories.md
+[UC-001]: ./uc-001/uc.md
+[923dde7]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/923dde7dc9b59d2c77eddc88336451193147c557
+[RC-007]: ./sqa/reviews/rc-007-ucd-001.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

docs/user-stories.md

@@ -0,0 +1,54 @@
+# User Stories
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | US-001 |
+| CrossReference | [UCD-001], [UC-001], [BC-001], [MIL-003], [RC-008] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-04 | Deprecated | Jens Tirsvad Nielsen | S01 | Initial version | [923dde7] |
+| 2026-10-04 | Accepted | Jens Tirsvad Nielsen | S01 | Accepted after review RC-008 | [c7164fe] |
+
+---
+
+## Purpose and Scope
+
+The stories for epic [MIL-003] (Console game): playing rounds and seeing the result. They support [BC-001] objective O1.
+
+## Story List
+
+### US-001.01 Guess which account has more followers
+
+- **As a** Player, **I want** to guess which of two accounts has more followers and keep playing while I am right, **so that** I can build a streak.
+- **Acceptance Criteria:**
+  - Given a new game, when it starts, then two different accounts A and B are shown.
+  - Given two accounts, when I guess the one with more followers, then my score goes up by one and the next round starts with that account as A and a new account as B.
+  - Given an invalid answer, when I submit it, then I am asked again and the round does not change.
+- **Traces to:** [UC-001], [MIL-003]
+- **Size:** one iteration.
+
+### US-001.02 See my final score
+
+- **As a** Player, **I want** to see my final score when the game ends, **so that** I know how well I did.
+- **Acceptance Criteria:**
+  - Given a round, when I guess the account with fewer followers, then the game ends and shows my final score.
+  - Given every account has been used, when no new account can be shown, then the game ends and shows my final score.
+- **Traces to:** [UC-001], [MIL-003]
+- **Size:** one iteration.
+
+## INVEST Check
+
+Both stories are Independent of each other in wording, Negotiable in detail, Valuable to the Player, Estimable, Small (one iteration) and Testable through the acceptance criteria. No exceptions.
+
+---
+
+[UCD-001]: ./use-case-diagram.md
+[UC-001]: ./uc-001/uc.md
+[BC-001]: ./business-case.md
+[MIL-003]: ./milestones/mil-003-console-game.md
+[923dde7]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/923dde7dc9b59d2c77eddc88336451193147c557
+[RC-008]: ./sqa/reviews/rc-008-us-001.md
+[c7164fe]: https://git.tirsystem.com/Tirsvad-Udemy-100_days_of_code/014-higher_lower/commit/c7164feab1333951bf6f557baf95a26764656be0

pyproject.toml

@@ -0,0 +1,35 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "higher-lower"
+version = "0.1.0"
+description = "Higher Lower console game: guess which Instagram account has more followers (Udemy 100 Days of Code, day 14)."
+readme = "README.md"
+requires-python = ">=3.13"
+license = { file = "LICENSE" }
+dependencies = []
+
+[project.optional-dependencies]
+dev = ["pytest>=9,<10", "ruff>=0.16,<0.17", "mypy>=2.4,<3"]
+
+[tool.setuptools.packages.find]
+where = ["src"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+pythonpath = ["src"]
+
+[tool.ruff]
+line-length = 88
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP", "FLY", "B"]
+
+[tool.ruff.lint.per-file-ignores]
+"src/higher_lower/game_data.py" = ["E501"] # assignment data kept verbatim
+
+[tool.mypy]
+strict = true
+mypy_path = "src"

src/higher_lower/__init__.py

@@ -0,0 +1,3 @@
+"""@package higher_lower
+@brief Higher Lower console game: guess which Instagram account has more followers.
+"""

src/higher_lower/__main__.py

@@ -0,0 +1,19 @@
+"""@file __main__.py
+@brief Entry point for `python -m higher_lower`.
+"""
+
+from higher_lower.constants import MSG_GOODBYE
+from higher_lower.game import play_game
+
+
+def main() -> None:
+    """@brief Play a game; leave quietly if the player quits with Ctrl+C or Ctrl+D."""
+    try:
+        play_game()
+    except (EOFError, KeyboardInterrupt):
+        print()
+        print(MSG_GOODBYE)
+
+
+if __name__ == "__main__":
+    main()

src/higher_lower/art.py

@@ -0,0 +1,45 @@
+"""@file art.py
+@brief ASCII art shown by the game, as given by the assignment.
+
+The lines are raw strings so the backslashes in the art survive unchanged.
+They are concatenated line by line, rather than written as one multi-line
+string, so Doxygen does not read the backticks in the art as markup.
+"""
+
+## The game logo.
+logo = (
+    "\n"
+    r"    __  ___       __             "
+    "\n"
+    r"   / / / (_)___ _/ /_  ___  _____"
+    "\n"
+    r"  / /_/ / / __ `/ __ \/ _ \/ ___/"
+    "\n"
+    r" / __  / / /_/ / / / /  __/ /    "
+    "\n"
+    r"/_/ ///_/\__, /_/ /_/\___/_/     "
+    "\n"
+    r"   / /  /____/_      _____  _____"
+    "\n"
+    r"  / /   / __ \ | /| / / _ \/ ___/"
+    "\n"
+    r" / /___/ /_/ / |/ |/ /  __/ /    "
+    "\n"
+    r"/_____/\____/|__/|__/\___/_/     "
+    "\n"
+)
+
+## The "vs" shown between the two accounts.
+vs = (
+    "\n"
+    r" _    __    "
+    "\n"
+    r"| |  / /____"
+    "\n"
+    r"| | / / ___/"
+    "\n"
+    r"| |/ (__  ) "
+    "\n"
+    r"|___/____(_)"
+    "\n"
+)

src/higher_lower/constants.py

@@ -0,0 +1,31 @@
+"""@file constants.py
+@brief Constants shared by the game modules.
+"""
+
+from typing import Final
+
+## Keys of an account dictionary.
+KEY_NAME: Final = "name"
+KEY_FOLLOWER_COUNT: Final = "follower_count"
+KEY_DESCRIPTION: Final = "description"
+KEY_COUNTRY: Final = "country"
+
+## The two choices the player can type, in lower case.
+CHOICE_A = "a"
+CHOICE_B = "b"
+
+## Score at the start of a game.
+START_SCORE = 0
+
+## How an account is described to the player.
+ACCOUNT_TEMPLATE = "{name}, a {description}, from {country}"
+
+## Texts shown to the player.
+MSG_COMPARE_A = "Compare A: {account}."
+MSG_AGAINST_B = "Against B: {account}."
+PROMPT_GUESS = "Who has more followers? Type 'A' or 'B': "
+MSG_INVALID_CHOICE = "Please type 'A' or 'B'."
+MSG_CORRECT = "You're right! Current score: {score}."
+MSG_WRONG = "Sorry, that's wrong. Final score: {score}"
+MSG_WIN = "You went through every account! Final score: {score}"
+MSG_GOODBYE = "Goodbye!"

src/higher_lower/game.py

@@ -0,0 +1,122 @@
+"""@file game.py
+@brief The interactive game: what the player sees, what they type, and the game loop.
+
+Input and output go through callables so tests can script a whole game.
+"""
+
+import random
+from collections.abc import Callable, Sequence
+
+from higher_lower.art import logo, vs
+from higher_lower.constants import (
+    CHOICE_A,
+    CHOICE_B,
+    KEY_FOLLOWER_COUNT,
+    KEY_NAME,
+    MSG_AGAINST_B,
+    MSG_COMPARE_A,
+    MSG_CORRECT,
+    MSG_INVALID_CHOICE,
+    MSG_WIN,
+    MSG_WRONG,
+    PROMPT_GUESS,
+    START_SCORE,
+)
+from higher_lower.game_data import Account, data
+from higher_lower.game_logic import (
+    check_answer,
+    format_data,
+    get_random_account,
+    pick_pair,
+)
+
+InputFunc = Callable[[str], str]
+OutputFunc = Callable[[str], None]
+
+
+def show_round(
+    account_a: Account,
+    account_b: Account,
+    output: OutputFunc = print,
+) -> None:
+    """@brief Show the two accounts the player compares.
+
+    @param account_a The account shown as A.
+    @param account_b The account shown as B.
+    @param output Where the text goes.
+    """
+    output(MSG_COMPARE_A.format(account=format_data(account_a)))
+    output(vs)
+    output(MSG_AGAINST_B.format(account=format_data(account_b)))
+
+
+def ask_choice(input_func: InputFunc = input, output: OutputFunc = print) -> str:
+    """@brief Ask for A or B until the player gives a valid answer.
+
+    @param input_func Reads one line of input, given the prompt.
+    @param output Where the invalid-answer message goes.
+    @return "a" or "b", in lower case.
+    """
+    while True:
+        answer = input_func(PROMPT_GUESS).strip().lower()
+        if answer in (CHOICE_A, CHOICE_B):
+            return answer
+        output(MSG_INVALID_CHOICE)
+
+
+def _pick_next_account(
+    accounts: Sequence[Account],
+    shown_names: set[str],
+    rng: random.Random | None,
+) -> Account | None:
+    """@brief Draw an account that has not been shown in this game.
+
+    @param accounts All accounts of the game.
+    @param shown_names Names of the accounts already shown.
+    @param rng Random generator, or None for the default.
+    @return A new account, or None if every account has been shown.
+    """
+    unused = [account for account in accounts if account[KEY_NAME] not in shown_names]
+    if not unused:
+        return None
+    return get_random_account(unused, rng)
+
+
+def play_game(
+    accounts: Sequence[Account] = data,
+    rng: random.Random | None = None,
+    input_func: InputFunc = input,
+    output: OutputFunc = print,
+) -> int:
+    """@brief Play one game, from the logo to the final score.
+
+    Each account is shown once per game. A right guess adds a point and
+    makes B the next A; a wrong guess, or running out of accounts, ends
+    the game.
+
+    @param accounts The accounts to play with; needs at least two entries.
+    @param rng Random generator; pass a seeded one for a repeatable game.
+    @param input_func Reads one line of input, given the prompt.
+    @param output Where the text goes.
+    @return The final score.
+    """
+    output(logo)
+    score = START_SCORE
+    account_a, account_b = pick_pair(accounts, rng)
+    shown_names = {account_a[KEY_NAME], account_b[KEY_NAME]}
+    while True:
+        show_round(account_a, account_b, output)
+        guess = ask_choice(input_func, output)
+        if not check_answer(
+            guess, account_a[KEY_FOLLOWER_COUNT], account_b[KEY_FOLLOWER_COUNT]
+        ):
+            output(MSG_WRONG.format(score=score))
+            return score
+        score += 1
+        output(MSG_CORRECT.format(score=score))
+        next_account = _pick_next_account(accounts, shown_names, rng)
+        if next_account is None:
+            output(MSG_WIN.format(score=score))
+            return score
+        account_a, account_b = account_b, next_account
+        shown_names.add(next_account[KEY_NAME])

src/higher_lower/game_data.py

@@ -0,0 +1,324 @@
+"""@file game_data.py
+@brief The accounts the player compares, as given by the assignment.
+
+The order is kept as in the assignment; the game compares follower counts,
+never list positions.
+"""
+
+from typing import TypedDict
+
+
+class Account(TypedDict):
+    """@brief One account the player can be asked about.
+
+    follower_count is in millions of Instagram followers.
+    """
+
+    name: str
+    follower_count: int
+    description: str
+    country: str
+
+
+data: list[Account] = [
+    {
+        "name": "Instagram",
+        "follower_count": 346,
+        "description": "Social media platform",
+        "country": "United States",
+    },
+    {
+        "name": "Cristiano Ronaldo",
+        "follower_count": 215,
+        "description": "Footballer",
+        "country": "Portugal",
+    },
+    {
+        "name": "Ariana Grande",
+        "follower_count": 183,
+        "description": "Musician and actress",
+        "country": "United States",
+    },
+    {
+        "name": "Dwayne Johnson",
+        "follower_count": 181,
+        "description": "Actor and professional wrestler",
+        "country": "United States",
+    },
+    {
+        "name": "Selena Gomez",
+        "follower_count": 174,
+        "description": "Musician and actress",
+        "country": "United States",
+    },
+    {
+        "name": "Kylie Jenner",
+        "follower_count": 172,
+        "description": "Reality TV personality and businesswoman and Self-Made Billionaire",
+        "country": "United States",
+    },
+    {
+        "name": "Kim Kardashian",
+        "follower_count": 167,
+        "description": "Reality TV personality and businesswoman",
+        "country": "United States",
+    },
+    {
+        "name": "Lionel Messi",
+        "follower_count": 149,
+        "description": "Footballer",
+        "country": "Argentina",
+    },
+    {
+        "name": "Beyoncé",
+        "follower_count": 145,
+        "description": "Musician",
+        "country": "United States",
+    },
+    {
+        "name": "Neymar",
+        "follower_count": 138,
+        "description": "Footballer",
+        "country": "Brasil",
+    },
+    {
+        "name": "National Geographic",
+        "follower_count": 135,
+        "description": "Magazine",
+        "country": "United States",
+    },
+    {
+        "name": "Justin Bieber",
+        "follower_count": 133,
+        "description": "Musician",
+        "country": "Canada",
+    },
+    {
+        "name": "Taylor Swift",
+        "follower_count": 131,
+        "description": "Musician",
+        "country": "United States",
+    },
+    {
+        "name": "Kendall Jenner",
+        "follower_count": 127,
+        "description": "Reality TV personality and Model",
+        "country": "United States",
+    },
+    {
+        "name": "Jennifer Lopez",
+        "follower_count": 119,
+        "description": "Musician and actress",
+        "country": "United States",
+    },
+    {
+        "name": "Nicki Minaj",
+        "follower_count": 113,
+        "description": "Musician",
+        "country": "Trinidad and Tobago",
+    },
+    {
+        "name": "Nike",
+        "follower_count": 109,
+        "description": "Sportswear multinational",
+        "country": "United States",
+    },
+    {
+        "name": "Khloé Kardashian",
+        "follower_count": 108,
+        "description": "Reality TV personality and businesswoman",
+        "country": "United States",
+    },
+    {
+        "name": "Miley Cyrus",
+        "follower_count": 107,
+        "description": "Musician and actress",
+        "country": "United States",
+    },
+    {
+        "name": "Katy Perry",
+        "follower_count": 94,
+        "description": "Musician",
+        "country": "United States",
+    },
+    {
+        "name": "Kourtney Kardashian",
+        "follower_count": 90,
+        "description": "Reality TV personality",
+        "country": "United States",
+    },
+    {
+        "name": "Kevin Hart",
+        "follower_count": 89,
+        "description": "Comedian and actor",
+        "country": "United States",
+    },
+    {
+        "name": "Ellen DeGeneres",
+        "follower_count": 87,
+        "description": "Comedian",
+        "country": "United States",
+    },
+    {
+        "name": "Real Madrid CF",
+        "follower_count": 86,
+        "description": "Football club",
+        "country": "Spain",
+    },
+    {
+        "name": "FC Barcelona",
+        "follower_count": 85,
+        "description": "Football club",
+        "country": "Spain",
+    },
+    {
+        "name": "Rihanna",
+        "follower_count": 81,
+        "description": "Musician and businesswoman",
+        "country": "Barbados",
+    },
+    {
+        "name": "Demi Lovato",
+        "follower_count": 80,
+        "description": "Musician and actress",
+        "country": "United States",
+    },
+    {
+        "name": "Victoria's Secret",
+        "follower_count": 69,
+        "description": "Lingerie brand",
+        "country": "United States",
+    },
+    {
+        "name": "Zendaya",
+        "follower_count": 68,
+        "description": "Actress and musician",
+        "country": "United States",
+    },
+    {
+        "name": "Shakira",
+        "follower_count": 66,
+        "description": "Musician",
+        "country": "Colombia",
+    },
+    {
+        "name": "Drake",
+        "follower_count": 65,
+        "description": "Musician",
+        "country": "Canada",
+    },
+    {
+        "name": "Chris Brown",
+        "follower_count": 64,
+        "description": "Musician",
+        "country": "United States",
+    },
+    {
+        "name": "LeBron James",
+        "follower_count": 63,
+        "description": "Basketball player",
+        "country": "United States",
+    },
+    {
+        "name": "Vin Diesel",
+        "follower_count": 62,
+        "description": "Actor",
+        "country": "United States",
+    },
+    {
+        "name": "Cardi B",
+        "follower_count": 67,
+        "description": "Musician",
+        "country": "United States",
+    },
+    {
+        "name": "David Beckham",
+        "follower_count": 82,
+        "description": "Footballer",
+        "country": "United Kingdom",
+    },
+    {
+        "name": "Billie Eilish",
+        "follower_count": 61,
+        "description": "Musician",
+        "country": "United States",
+    },
+    {
+        "name": "Justin Timberlake",
+        "follower_count": 59,
+        "description": "Musician and actor",
+        "country": "United States",
+    },
+    {
+        "name": "UEFA Champions League",
+        "follower_count": 58,
+        "description": "Club football competition",
+        "country": "Europe",
+    },
+    {
+        "name": "NASA",
+        "follower_count": 56,
+        "description": "Space agency",
+        "country": "United States",
+    },
+    {
+        "name": "Emma Watson",
+        "follower_count": 56,
+        "description": "Actress",
+        "country": "United Kingdom",
+    },
+    {
+        "name": "Shawn Mendes",
+        "follower_count": 57,
+        "description": "Musician",
+        "country": "Canada",
+    },
+    {
+        "name": "Virat Kohli",
+        "follower_count": 55,
+        "description": "Cricketer",
+        "country": "India",
+    },
+    {
+        "name": "Gigi Hadid",
+        "follower_count": 54,
+        "description": "Model",
+        "country": "United States",
+    },
+    {
+        "name": "Priyanka Chopra Jonas",
+        "follower_count": 53,
+        "description": "Actress and musician",
+        "country": "India",
+    },
+    {
+        "name": "9GAG",
+        "follower_count": 52,
+        "description": "Social media platform",
+        "country": "China",
+    },
+    {
+        "name": "Ronaldinho",
+        "follower_count": 51,
+        "description": "Footballer",
+        "country": "Brasil",
+    },
+    {
+        "name": "Maluma",
+        "follower_count": 50,
+        "description": "Musician",
+        "country": "Colombia",
+    },
+    {
+        "name": "Camila Cabello",
+        "follower_count": 49,
+        "description": "Musician",
+        "country": "Cuba",
+    },
+    {
+        "name": "NBA",
+        "follower_count": 47,
+        "description": "Club Basketball Competition",
+        "country": "United States",
+    },
+]

src/higher_lower/game_logic.py

@@ -0,0 +1,78 @@
+"""@file game_logic.py
+@brief Pure game functions: draw accounts, describe them, check guesses.
+"""
+
+import random
+from collections.abc import Sequence
+
+from higher_lower.constants import (
+    ACCOUNT_TEMPLATE,
+    CHOICE_A,
+    CHOICE_B,
+    KEY_COUNTRY,
+    KEY_DESCRIPTION,
+    KEY_NAME,
+)
+from higher_lower.game_data import Account, data
+
+_DEFAULT_RNG = random.Random()
+
+
+def get_random_account(
+    accounts: Sequence[Account] = data,
+    rng: random.Random | None = None,
+) -> Account:
+    """@brief Return one random account.
+
+    @param accounts The accounts to draw from.
+    @param rng Random generator; pass a seeded one to make the draw repeatable.
+    @return A random entry of accounts.
+    """
+    return (rng or _DEFAULT_RNG).choice(accounts)
+
+
+def pick_pair(
+    accounts: Sequence[Account] = data,
+    rng: random.Random | None = None,
+) -> tuple[Account, Account]:
+    """@brief Return two different random accounts.
+
+    @param accounts The accounts to draw from; needs at least two entries.
+    @param rng Random generator; pass a seeded one to make the draw repeatable.
+    @return The accounts A and B, never the same entry.
+    @throws ValueError If accounts has fewer than two entries.
+    """
+    first, second = (rng or _DEFAULT_RNG).sample(accounts, 2)
+    return first, second
+
+
+def format_data(account: Account) -> str:
+    """@brief Describe an account for the player.
+
+    @param account The account to describe.
+    @return Text such as "Nike, a Sportswear multinational, from United States".
+    """
+    return ACCOUNT_TEMPLATE.format(
+        name=account[KEY_NAME],
+        description=account[KEY_DESCRIPTION],
+        country=account[KEY_COUNTRY],
+    )
+
+
+def check_answer(guess: str, a_followers: int, b_followers: int) -> bool:
+    """@brief Tell whether the guess names the account with more followers.
+
+    Equal follower counts make either choice correct.
+
+    @param guess "a" or "b", in any case.
+    @param a_followers Follower count of account A.
+    @param b_followers Follower count of account B.
+    @return True if the guess is right.
+    @throws ValueError If guess is neither "a" nor "b".
+    """
+    choice = guess.lower()
+    if choice == CHOICE_A:
+        return a_followers >= b_followers
+    if choice == CHOICE_B:
+        return b_followers >= a_followers
+    raise ValueError(f"guess must be {CHOICE_A!r} or {CHOICE_B!r}, got {guess!r}")

tests/test_game.py

@@ -0,0 +1,161 @@
+"""@file test_game.py
+@brief Tests for the game loop, run with scripted input and no real console.
+"""
+
+import io
+import random
+from collections.abc import Callable, Iterable, Sequence
+
+import pytest
+
+from higher_lower import __main__ as entry_point
+from higher_lower.art import logo
+from higher_lower.game import ask_choice, play_game, show_round
+from higher_lower.game_data import Account
+
+ACCOUNTS: list[Account] = [
+    {
+        "name": "First",
+        "follower_count": 30,
+        "description": "Test one",
+        "country": "Denmark",
+    },
+    {
+        "name": "Second",
+        "follower_count": 20,
+        "description": "Test two",
+        "country": "Norway",
+    },
+    {
+        "name": "Third",
+        "follower_count": 10,
+        "description": "Test three",
+        "country": "Sweden",
+    },
+]
+
+
+class FirstRng(random.Random):
+    """@brief Random generator that takes the first entries, so a game is fixed."""
+
+    def sample(  # type: ignore[override]
+        self, population: Sequence[Account], k: int, **kwargs: object
+    ) -> list[Account]:
+        """@brief Return the first k entries."""
+        return list(population)[:k]
+
+    def choice(self, seq: Sequence[Account]) -> Account:  # type: ignore[override]
+        """@brief Return the first entry."""
+        return seq[0]
+
+
+def scripted(answers: Iterable[str]) -> Callable[[str], str]:
+    """@brief Make an input function that gives the answers one by one.
+
+    @param answers The answers to give.
+    @return A function with the signature of input().
+    """
+    iterator = iter(answers)
+    return lambda _prompt: next(iterator)
+
+
+def run_game(answers: Iterable[str]) -> tuple[int, str]:
+    """@brief Play a fixed game and return the score and everything shown.
+
+    @param answers The answers the player gives.
+    @return The final score and the output joined with newlines.
+    """
+    lines: list[str] = []
+    score = play_game(ACCOUNTS, FirstRng(), scripted(answers), lines.append)
+    return score, "\n".join(lines)
+
+
+def test_show_round_shows_both_accounts() -> None:
+    """@brief Both accounts are described, with the vs art between them."""
+    lines: list[str] = []
+    show_round(ACCOUNTS[0], ACCOUNTS[1], lines.append)
+    assert lines[0] == "Compare A: First, a Test one, from Denmark."
+    assert lines[2] == "Against B: Second, a Test two, from Norway."
+
+
+@pytest.mark.parametrize("typed", ["a", "A", " a "])
+def test_ask_choice_accepts_a(typed: str) -> None:
+    """@brief A is accepted in any case and with spaces around it."""
+    assert ask_choice(scripted([typed]), lambda _line: None) == "a"
+
+
+def test_ask_choice_asks_again_after_an_invalid_answer() -> None:
+    """@brief Invalid answers are rejected and the player is asked again."""
+    lines: list[str] = []
+    assert ask_choice(scripted(["x", "", "b"]), lines.append) == "b"
+    assert len(lines) == 2
+
+
+def test_correct_streak_adds_a_point_per_round() -> None:
+    """@brief Each right guess adds one to the score and B becomes the next A."""
+    score, shown = run_game(["a", "a"])
+    assert score == 2
+    assert "Current score: 1." in shown
+    assert "Compare A: Second" in shown
+
+
+def test_wrong_first_guess_ends_the_game_with_zero() -> None:
+    """@brief A wrong guess ends the game and shows the final score."""
+    score, shown = run_game(["b"])
+    assert score == 0
+    assert "Sorry, that's wrong. Final score: 0" in shown
+
+
+def test_wrong_guess_after_a_point_keeps_the_score() -> None:
+    """@brief The final score is the number of right guesses."""
+    score, shown = run_game(["a", "b"])
+    assert score == 1
+    assert "Final score: 1" in shown
+
+
+def test_invalid_input_does_not_change_the_round() -> None:
+    """@brief An invalid answer is re-asked without ending the game or scoring."""
+    score, shown = run_game(["x", "a", "a"])
+    assert score == 2
+    assert shown.count("Compare A: First") == 1
+
+
+def test_game_ends_with_a_win_when_the_accounts_run_out() -> None:
+    """@brief Using every account ends the game instead of failing."""
+    score, shown = run_game(["a", "a"])
+    assert score == 2
+    assert "You went through every account!" in shown
+
+
+def test_game_starts_with_the_logo() -> None:
+    """@brief The logo is shown first."""
+    _score, shown = run_game(["b"])
+    assert shown.startswith(logo)
+
+
+def test_full_game_with_the_assignment_data_ends() -> None:
+    """@brief A game with the real data set ends with a final score."""
+    lines: list[str] = []
+    score = play_game(
+        rng=random.Random(5), input_func=lambda _prompt: "a", output=lines.append
+    )
+    assert score >= 0
+    assert "Final score" in lines[-1]
+
+
+def test_main_plays_a_game(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
+    """@brief main() runs a game on the console."""
+    monkeypatch.setattr("sys.stdin", io.StringIO("a\n" * 100))
+    entry_point.main()
+    assert "Final score" in capsys.readouterr().out
+
+
+def test_main_leaves_quietly_on_end_of_input(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
+    """@brief Ctrl+D ends the game with a goodbye, not a traceback."""
+    monkeypatch.setattr("sys.stdin", io.StringIO(""))
+    entry_point.main()
+    assert "Goodbye!" in capsys.readouterr().out

tests/test_game_data.py

@@ -0,0 +1,46 @@
+"""@file test_game_data.py
+@brief Tests for the assignment data set and art.
+"""
+
+from higher_lower.art import logo, vs
+from higher_lower.constants import (
+    KEY_COUNTRY,
+    KEY_DESCRIPTION,
+    KEY_FOLLOWER_COUNT,
+    KEY_NAME,
+)
+from higher_lower.game_data import data
+
+EXPECTED_KEYS = {KEY_NAME, KEY_FOLLOWER_COUNT, KEY_DESCRIPTION, KEY_COUNTRY}
+
+
+def test_data_has_fifty_accounts() -> None:
+    """@brief The assignment data set has 50 entries."""
+    assert len(data) == 50
+
+
+def test_every_account_has_the_required_keys() -> None:
+    """@brief Every entry has exactly the four assignment keys."""
+    assert all(set(account) == EXPECTED_KEYS for account in data)
+
+
+def test_follower_counts_are_positive_integers() -> None:
+    """@brief Follower counts are positive integers."""
+    assert all(
+        isinstance(account[KEY_FOLLOWER_COUNT], int) and account[KEY_FOLLOWER_COUNT] > 0
+        for account in data
+    )
+
+
+def test_account_names_are_unique() -> None:
+    """@brief No account appears twice."""
+    names = [account[KEY_NAME] for account in data]
+    assert len(names) == len(set(names))
+
+
+def test_art_is_available() -> None:
+    """@brief The logo and the vs art keep their shape, including backslashes."""
+    assert len(logo.splitlines()) == 10
+    assert "\\" in logo
+    assert len(vs.splitlines()) == 6
+    assert "|___/____(_)" in vs

tests/test_game_logic.py

@@ -0,0 +1,88 @@
+"""@file test_game_logic.py
+@brief Tests for the pure game functions.
+"""
+
+import random
+
+import pytest
+
+from higher_lower.constants import KEY_NAME
+from higher_lower.game_data import Account, data
+from higher_lower.game_logic import (
+    check_answer,
+    format_data,
+    get_random_account,
+    pick_pair,
+)
+
+
+def test_get_random_account_returns_an_entry_of_the_data() -> None:
+    """@brief The drawn account comes from the data set."""
+    assert get_random_account(rng=random.Random(1)) in data
+
+
+def test_get_random_account_is_repeatable_with_a_seed() -> None:
+    """@brief The same seed draws the same account."""
+    assert get_random_account(rng=random.Random(7)) == get_random_account(
+        rng=random.Random(7)
+    )
+
+
+def test_pick_pair_never_returns_the_same_account() -> None:
+    """@brief A and B are always different entries."""
+    rng = random.Random(0)
+    for _ in range(200):
+        first, second = pick_pair(rng=rng)
+        assert first[KEY_NAME] != second[KEY_NAME]
+
+
+def test_pick_pair_with_two_accounts_returns_both() -> None:
+    """@brief With only two accounts, the pair holds both of them."""
+    two = data[:2]
+    first, second = pick_pair(two, random.Random(3))
+    assert {first[KEY_NAME], second[KEY_NAME]} == {a[KEY_NAME] for a in two}
+
+
+def test_pick_pair_with_one_account_raises() -> None:
+    """@brief A pair cannot be drawn from a single account."""
+    with pytest.raises(ValueError):
+        pick_pair(data[:1])
+
+
+def test_format_data_describes_the_account() -> None:
+    """@brief The description holds name, description and country."""
+    account: Account = {
+        "name": "Nike",
+        "follower_count": 109,
+        "description": "Sportswear multinational",
+        "country": "United States",
+    }
+    assert (
+        format_data(account) == "Nike, a Sportswear multinational, from United States"
+    )
+
+
+@pytest.mark.parametrize(
+    ("guess", "a_followers", "b_followers", "expected"),
+    [
+        ("a", 200, 100, True),
+        ("a", 100, 200, False),
+        ("b", 100, 200, True),
+        ("b", 200, 100, False),
+        ("A", 200, 100, True),
+        ("B", 100, 200, True),
+        ("a", 100, 100, True),
+        ("b", 100, 100, True),
+    ],
+)
+def test_check_answer(
+    guess: str, a_followers: int, b_followers: int, expected: bool
+) -> None:
+    """@brief The answer is right for the higher account, and for either on a tie."""
+    assert check_answer(guess, a_followers, b_followers) is expected
+
+
+def test_check_answer_rejects_an_unknown_choice() -> None:
+    """@brief A guess other than a or b is an error."""
+    with pytest.raises(ValueError):
+        check_answer("c", 1, 2)

tests/test_smoke.py

@@ -0,0 +1,16 @@
+"""@file test_smoke.py
+@brief Smoke test: the package and its entry point can be imported.
+"""
+
+import higher_lower
+from higher_lower import __main__ as entry_point
+
+
+def test_package_imports() -> None:
+    """@brief The package imports without side effects."""
+    assert higher_lower.__doc__
+
+
+def test_entry_point_is_callable() -> None:
+    """@brief The entry point exists; importing it does not start a game."""
+    assert callable(entry_point.main)