README.md

@@ -81,12 +81,28 @@ The program is added step by step (one pull request per lecture step):
 
 | Step | Status |
 | --- | --- |
-| 1. Scrape the Billboard Hot 100 | planned in milestone 3 |
+| 1. Scrape the Billboard Hot 100 | done (below) |
 | 2. YouTube Music authentication | planned in milestone 4 |
 | 3. Create the playlist | planned in milestone 5 |
 | 4. Search and add songs | planned in milestone 6 |
 
-The run command and a screenshot for each step are added with the step.
+### Step 1 - Scrape the Billboard Hot 100
+
+```bash
+python -m musical_time_machine
+```
+
+The program asks for a date in the format `YYYY-MM-DD` and prints the 100 songs of that chart as `rank. title - artist`. Use a date that Bakeboard has, for example `2026-04-18`. `scrape_titles` returns the titles as a Python list; a date in the wrong format or a chart that does not exist ends the program with a clear message.
+
+The chart page on Bakeboard:
+
+![The Bakeboard Hot 100 page for 2026-04-18](docs/wiki/images/step1-bakeboard-page.png)
+
+The program's output for the same date (rendered from the real output of the run, not a photo of a terminal window):
+
+![Output of step 1 for 2026-04-18](docs/wiki/images/step1-terminal-output.png)
+
+The screenshots and the instructions of the next steps are added with each step.
 
 ## 🧪 Tests
 

docs/artifact-registry.md

@@ -17,7 +17,7 @@ document of a type. `Primary File` may contain a glob (e.g.
 | MIL | Milestone / Gateway | docs/milestones/mil-*.md | 008 |
 | GOV | Governance / ARB Workflow | docs/sqa/governance.md | 002 |
 | TM | Traceability Matrix | docs/sqa/traceability-matrix.md | 002 |
-| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 013 |
+| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 014 |
 
 ## Languages
 

docs/sqa/reviews/rc-013-mil-003-code.md

@@ -0,0 +1,61 @@
+# Review of the code of MIL-003
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-013 |
+| CrossReference | [MIL-003], [QC-PY-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-28 | Proposed | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | pending |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-003] (the code of its pull request, `src/` and `tests/`)
+- Checklist used: [QC-PY-001] (`QC-PY-001`)
+- Scope: full review
+- Language and domain: n/a
+- Language reviewer: none
+- Mode: autonomous, not independent (reviewer is `AI as stand-in for S01`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | snake_case modules and functions, PascalCase classes (Song, BakeboardChartSource), UPPER_SNAKE constants. |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names state purpose (parse_chart_date, ChartUnavailableError). |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | ruff format and ruff check report no finding. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | Every function is annotated including -> None; ruff does not flag it and the code was read. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | No bare except; requests errors are translated with raise ... from. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults; no shadowed builtins (the CLI parameter `read`/`write` do not shadow builtins). |
+| 7 | Files, locks and connections are managed with context managers | N-A | No files or connections are opened by the code; requests.get is a one-shot call. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how | Pass | Doxygen comments on all public items; doxygen has 0 warnings. |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | Pass | logging is used for the skipped-row warning; user-facing output goes through the injected writer; nothing secret is logged. |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | N-A | No Design Class Diagram exists; all tasks are technical (BC-001 scope); the layers follow the clean-architecture skill. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | 31 tests, 96 % coverage, no network: a stored page and fake sources; names state the behaviour. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment | Pass | No Any in the source. |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused | Pass | requests and beautifulsoup4 are used by infrastructure; ytmusicapi is used from MIL-004 (declared now by the accepted plan). |
+| 14 | Each piece of knowledge (a business rule, constant, format, validation or query) is defined in one place; code is merged only where it expresses the same knowledge, not where it merely looks alike | Pass | Selectors, messages and the date format are defined once in constants.py; the date is parsed in one function. |
+| 15 | Imports point inward: business-rule modules import no framework, database, UI or delivery-mechanism code, and there are no import cycles | Pass | domain imports nothing; application imports domain; infrastructure imports application and domain; presentation is the composition root. |
+| 16 | SOLID holds: a class or module has one reason to change; new behaviour is added by extension, not by editing a type test in several places; subclasses honour the contract of their base; protocols are narrow; high-level code depends on protocols or abstract types and receives its implementations | Pass | ChartSource is a narrow Protocol; the CLI depends on it, the Bakeboard source is injected. |
+| 17 | Source is laid out in the layers and folders of the clean architecture folder structure (`domain`, `application`, `infrastructure`, `presentation` packages under `src/`, and `unit`, `integration` and `e2e` under `tests/`), in `snake_case`, and imports between the layers point inward | Pass | src layers and tests/unit/<layer> plus tests/integration exist. |
+| 18 | File and folder names are English, contain no space and no character outside letters, digits, `-`, `_` and `.`, and follow the casing of the language for files | Pass | File names are English snake_case. |
+
+## Overall Verdict
+
+Go — every Mandatory criterion passes or does not apply; no blocking finding.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | S01 | - |
+
+---
+
+[MIL-003]: ../../milestones/mil-003-step-1-scrape-billboard.md
+[QC-PY-001]: ../../../framework/qc/code/qc-programming-python.md

docs/sqa/traceability-matrix.md

@@ -27,7 +27,7 @@ Tracks backward and forward links between artifact instances so that the traceab
 | [GOV-001] | GOV | en | it | [BC-001], [SA-001] | [TM-001] | [RC-004] |
 | [MIL-001] | MIL | en | it | [BC-001], [PP-001] | [MIL-002] | [RC-005] |
 | [MIL-002] | MIL | en | it | [MIL-001] | [MIL-003] | [RC-006], [RC-012] |
-| [MIL-003] | MIL | en | it | [MIL-002] | [MIL-004] | [RC-007] |
+| [MIL-003] | MIL | en | it | [MIL-002] | [MIL-004] | [RC-007], [RC-013] |
 | [MIL-004] | MIL | en | it | [MIL-003] | [MIL-005] | [RC-008] |
 | [MIL-005] | MIL | en | it | [MIL-004] | [MIL-006] | [RC-009] |
 | [MIL-006] | MIL | en | it | [MIL-005] | [MIL-007] | [RC-010] |
@@ -82,3 +82,4 @@ Tracks backward and forward links between artifact instances so that the traceab
 [RC-011]: ./reviews/rc-011-mil-007.md
 [01e016e]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/046-scraping-the-billboard/commit/01e016e15dd93cface4f4ae9e9e99919e0aace2b
 [RC-012]: ./reviews/rc-012-mil-002-code.md
+[RC-013]: ./reviews/rc-013-mil-003-code.md

pyproject.toml

@@ -19,6 +19,9 @@ dev = [
     "ruff>=0.17",
 ]
 
+[project.scripts]
+musical-time-machine = "musical_time_machine.presentation.cli:main"
+
 [tool.setuptools.packages.find]
 where = ["src"]
 

src/musical_time_machine/__main__.py

@@ -0,0 +1,7 @@
+"""@file
+@brief Entry point for `python -m musical_time_machine`.
+"""
+
+from musical_time_machine.presentation.cli import main
+
+raise SystemExit(main())

src/musical_time_machine/application/ports.py

@@ -0,0 +1,20 @@
+"""@file
+@brief Ports the use cases need from the outside world.
+"""
+
+from datetime import date
+from typing import Protocol
+
+from musical_time_machine.domain.song import Song
+
+
+class ChartSource(Protocol):
+    """@brief Supplies the songs of one chart."""
+
+    def songs_for(self, chart_date: date) -> list[Song]:
+        """@brief Get the songs of the chart of a date.
+
+        @param chart_date Date of the chart.
+        @return The songs in chart order.
+        """
+        ...

src/musical_time_machine/application/use_cases.py

@@ -0,0 +1,28 @@
+"""@file
+@brief Use cases of the Musical Time Machine.
+"""
+
+from datetime import date
+
+from musical_time_machine.application.ports import ChartSource
+from musical_time_machine.domain.song import Song
+
+
+def scrape_songs(chart_date: date, source: ChartSource) -> list[Song]:
+    """@brief Get the songs of the chart of a date.
+
+    @param chart_date Date of the chart.
+    @param source Where the chart comes from.
+    @return The songs in chart order.
+    """
+    return source.songs_for(chart_date)
+
+
+def scrape_titles(chart_date: date, source: ChartSource) -> list[str]:
+    """@brief Get the song titles of the chart of a date.
+
+    @param chart_date Date of the chart.
+    @param source Where the chart comes from.
+    @return The titles in chart order.
+    """
+    return [song.title for song in scrape_songs(chart_date, source)]

src/musical_time_machine/constants.py

@@ -45,6 +45,33 @@ SELECTOR_TITLE: Final[str] = "h3.chart-entry__title"
 SELECTOR_ARTIST: Final[str] = "span.chart-entry__artist"
 ## @}
 
+## @name Command line
+## @{
+
+## @brief Prompt asking for the chart date.
+DATE_PROMPT: Final[str] = (
+    "Which year do you want to travel to? Type the date in this format YYYY-MM-DD: "
+)
+
+## @brief Message for a date that is not YYYY-MM-DD; format with the entered text.
+INVALID_DATE_MESSAGE: Final[str] = "'{text}' is not a valid date; use the format YYYY-MM-DD."
+
+## @brief Message when the chart page cannot be fetched; format with the cause.
+CHART_UNAVAILABLE_MESSAGE: Final[str] = "The chart could not be fetched: {reason}"
+
+## @brief Message when the page holds no songs; format with the chart date.
+CHART_PARSE_MESSAGE: Final[str] = "No songs were found on the chart page for {date}."
+
+## @brief Line format of the printed song list.
+SONG_LINE_TEMPLATE: Final[str] = "{position}. {title} - {artist}"
+
+## @brief Process exit code on success.
+EXIT_OK: Final[int] = 0
+
+## @brief Process exit code when a domain error stopped the run.
+EXIT_FAILURE: Final[int] = 1
+## @}
+
 ## @name YouTube Music
 ## @{
 

src/musical_time_machine/domain/chart_date.py

@@ -0,0 +1,26 @@
+"""@file
+@brief Validation of the chart date.
+"""
+
+from datetime import date, datetime
+
+from musical_time_machine.constants import DATE_FORMAT, INVALID_DATE_MESSAGE
+from musical_time_machine.domain.errors import InvalidChartDateError
+
+
+def parse_chart_date(text: str) -> date:
+    """@brief Turn YYYY-MM-DD text into a date.
+
+    @param text The text the user entered.
+    @return The calendar date.
+    @throws InvalidChartDateError when the text is not a real date in that format.
+    """
+    cleaned = text.strip()
+    try:
+        parsed = datetime.strptime(cleaned, DATE_FORMAT).date()
+    except ValueError as error:
+        raise InvalidChartDateError(INVALID_DATE_MESSAGE.format(text=cleaned)) from error
+    if parsed.strftime(DATE_FORMAT) != cleaned:
+        # strptime accepts "2026-4-8"; the contract is the zero-padded form.
+        raise InvalidChartDateError(INVALID_DATE_MESSAGE.format(text=cleaned))
+    return parsed

src/musical_time_machine/domain/errors.py

@@ -0,0 +1,19 @@
+"""@file
+@brief Errors raised by the business rules of the Musical Time Machine.
+"""
+
+
+class MusicalTimeMachineError(Exception):
+    """@brief Base class of every domain error."""
+
+
+class InvalidChartDateError(MusicalTimeMachineError):
+    """@brief The entered text is not a valid YYYY-MM-DD date."""
+
+
+class ChartUnavailableError(MusicalTimeMachineError):
+    """@brief The chart page could not be fetched (missing page or HTTP error)."""
+
+
+class ChartParseError(MusicalTimeMachineError):
+    """@brief The chart page holds no songs."""

src/musical_time_machine/domain/song.py

@@ -0,0 +1,17 @@
+"""@file
+@brief The Song value object.
+"""
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True, slots=True)
+class Song:
+    """@brief One chart entry.
+
+    @param title Song title.
+    @param artist Performing artist.
+    """
+
+    title: str
+    artist: str

src/musical_time_machine/infrastructure/bakeboard.py

@@ -0,0 +1,88 @@
+"""@file
+@brief Bakeboard Hot 100 clone as a chart source.
+"""
+
+import logging
+from collections.abc import Callable
+from datetime import date
+
+import requests
+from bs4 import BeautifulSoup
+
+from musical_time_machine.constants import (
+    BASE_URL,
+    CHART_PARSE_MESSAGE,
+    CHART_UNAVAILABLE_MESSAGE,
+    DATE_FORMAT,
+    REQUEST_HEADERS,
+    REQUEST_TIMEOUT_SECONDS,
+    SELECTOR_ARTIST,
+    SELECTOR_ROW,
+    SELECTOR_TITLE,
+)
+from musical_time_machine.domain.errors import ChartParseError, ChartUnavailableError
+from musical_time_machine.domain.song import Song
+
+_logger = logging.getLogger(__name__)
+
+
+def parse_chart(html: str) -> list[Song]:
+    """@brief Extract the songs from a chart page.
+
+    @param html The page markup.
+    @return The songs in page order.
+    @throws ChartParseError when the page holds no songs.
+    """
+    soup = BeautifulSoup(html, "html.parser")
+    songs: list[Song] = []
+    for row in soup.select(SELECTOR_ROW):
+        title = row.select_one(SELECTOR_TITLE)
+        artist = row.select_one(SELECTOR_ARTIST)
+        if title is None or artist is None:
+            _logger.warning("Skipping a chart row without title or artist")
+            continue
+        songs.append(Song(title=title.get_text(strip=True), artist=artist.get_text(strip=True)))
+    if not songs:
+        raise ChartParseError("No songs found on the chart page")
+    return songs
+
+
+def fetch_page(url: str) -> str:
+    """@brief Download a page over HTTP.
+
+    @param url Address of the page.
+    @return The page markup.
+    @throws requests.RequestException when the request fails or answers with an HTTP error.
+    """
+    response = requests.get(url, headers=REQUEST_HEADERS, timeout=REQUEST_TIMEOUT_SECONDS)
+    response.raise_for_status()
+    return response.text
+
+
+class BakeboardChartSource:
+    """@brief ChartSource that scrapes the Bakeboard site."""
+
+    def __init__(self, fetch: Callable[[str], str] = fetch_page) -> None:
+        """@brief Create the source.
+
+        @param fetch Function that downloads a URL; replaced in tests.
+        """
+        self._fetch = fetch
+
+    def songs_for(self, chart_date: date) -> list[Song]:
+        """@brief Get the songs of the chart of a date.
+
+        @param chart_date Date of the chart.
+        @return The songs in chart order.
+        @throws ChartUnavailableError when the page cannot be fetched.
+        @throws ChartParseError when the page holds no songs.
+        """
+        stamp = chart_date.strftime(DATE_FORMAT)
+        try:
+            html = self._fetch(f"{BASE_URL}{stamp}/")
+        except requests.RequestException as error:
+            raise ChartUnavailableError(CHART_UNAVAILABLE_MESSAGE.format(reason=error)) from error
+        try:
+            return parse_chart(html)
+        except ChartParseError as error:
+            raise ChartParseError(CHART_PARSE_MESSAGE.format(date=stamp)) from error

src/musical_time_machine/presentation/cli.py

@@ -0,0 +1,40 @@
+"""@file
+@brief Command line entry point and composition root.
+"""
+
+from collections.abc import Callable
+
+from musical_time_machine.application.ports import ChartSource
+from musical_time_machine.application.use_cases import scrape_songs
+from musical_time_machine.constants import DATE_PROMPT, EXIT_FAILURE, EXIT_OK, SONG_LINE_TEMPLATE
+from musical_time_machine.domain.chart_date import parse_chart_date
+from musical_time_machine.domain.errors import MusicalTimeMachineError
+from musical_time_machine.infrastructure.bakeboard import BakeboardChartSource
+
+
+def main(
+    argv: list[str] | None = None,
+    *,
+    source: ChartSource | None = None,
+    read: Callable[[str], str] = input,
+    write: Callable[[str], None] = print,
+) -> int:
+    """@brief Ask for a date and print the songs of that chart.
+
+    @param argv Command line arguments; unused, kept for the entry point contract.
+    @param source Chart source; the Bakeboard site when omitted.
+    @param read Function that prompts and returns the user's answer.
+    @param write Function that shows one line to the user.
+    @return Process exit code: 0 on success, 1 when a domain error stopped the run.
+    """
+    del argv
+    chart_source = source if source is not None else BakeboardChartSource()
+    try:
+        chart_date = parse_chart_date(read(DATE_PROMPT))
+        songs = scrape_songs(chart_date, chart_source)
+    except MusicalTimeMachineError as error:
+        write(str(error))
+        return EXIT_FAILURE
+    for position, song in enumerate(songs, start=1):
+        write(SONG_LINE_TEMPLATE.format(position=position, title=song.title, artist=song.artist))
+    return EXIT_OK

tests/conftest.py

@@ -0,0 +1,33 @@
+"""@file
+@brief Shared fixtures: the stored Bakeboard page and a fake chart source.
+"""
+
+from datetime import date
+from pathlib import Path
+
+import pytest
+
+from musical_time_machine.domain.song import Song
+
+FIXTURE_PAGE = Path(__file__).parent / "fixtures" / "bakeboard-2026-04-18.html"
+
+
+@pytest.fixture
+def chart_html() -> str:
+    """@brief The stored 2026-04-18 chart page."""
+    return FIXTURE_PAGE.read_text(encoding="utf-8")
+
+
+class FakeChartSource:
+    """@brief ChartSource returning fixed songs, or raising a given error."""
+
+    def __init__(self, songs: list[Song] | None = None, error: Exception | None = None) -> None:
+        self._songs = songs or []
+        self._error = error
+        self.requested: list[date] = []
+
+    def songs_for(self, chart_date: date) -> list[Song]:
+        self.requested.append(chart_date)
+        if self._error is not None:
+            raise self._error
+        return self._songs

tests/integration/test_bakeboard_chart_source.py

@@ -0,0 +1,48 @@
+"""@file
+@brief Integration tests of BakeboardChartSource with an injected fetch (no network).
+"""
+
+from datetime import date
+
+import pytest
+import requests
+
+from musical_time_machine.constants import BASE_URL, CHART_SIZE
+from musical_time_machine.domain.errors import ChartParseError, ChartUnavailableError
+from musical_time_machine.infrastructure.bakeboard import BakeboardChartSource
+
+
+def test_songs_for_requests_dated_url_and_parses_fixture(chart_html: str) -> None:
+    urls: list[str] = []
+
+    def fetch(url: str) -> str:
+        urls.append(url)
+        return chart_html
+
+    songs = BakeboardChartSource(fetch).songs_for(date(2026, 4, 18))
+
+    assert urls == [f"{BASE_URL}2026-04-18/"]
+    assert len(songs) == CHART_SIZE
+
+
+def test_songs_for_maps_connection_error_to_chart_unavailable() -> None:
+    def fetch(url: str) -> str:
+        raise requests.ConnectionError("offline")
+
+    with pytest.raises(ChartUnavailableError):
+        BakeboardChartSource(fetch).songs_for(date(2026, 4, 18))
+
+
+def test_songs_for_raises_parse_error_for_empty_page_naming_the_date() -> None:
+    source = BakeboardChartSource(lambda url: "<html></html>")
+
+    with pytest.raises(ChartParseError, match="2026-04-18"):
+        source.songs_for(date(2026, 4, 18))
+
+
+def test_songs_for_maps_http_error_to_chart_unavailable() -> None:
+    def fetch(url: str) -> str:
+        raise requests.HTTPError("404 Not Found")
+
+    with pytest.raises(ChartUnavailableError, match="404"):
+        BakeboardChartSource(fetch).songs_for(date(2026, 4, 18))

tests/unit/application/test_use_cases.py

@@ -0,0 +1,32 @@
+"""@file
+@brief Tests of the scrape use cases with a fake chart source.
+"""
+
+from datetime import date
+
+import pytest
+from conftest import FakeChartSource
+
+from musical_time_machine.application.use_cases import scrape_songs, scrape_titles
+from musical_time_machine.domain.errors import ChartUnavailableError
+from musical_time_machine.domain.song import Song
+
+SONGS = [Song("One", "A"), Song("Two", "B")]
+
+
+def test_scrape_songs_returns_source_songs_for_the_date() -> None:
+    source = FakeChartSource(SONGS)
+
+    assert scrape_songs(date(2026, 4, 18), source) == SONGS
+    assert source.requested == [date(2026, 4, 18)]
+
+
+def test_scrape_titles_returns_titles_in_order() -> None:
+    assert scrape_titles(date(2026, 4, 18), FakeChartSource(SONGS)) == ["One", "Two"]
+
+
+def test_scrape_titles_propagates_source_error() -> None:
+    source = FakeChartSource(error=ChartUnavailableError("down"))
+
+    with pytest.raises(ChartUnavailableError):
+        scrape_titles(date(2026, 4, 18), source)

tests/unit/domain/test_chart_date.py

@@ -0,0 +1,38 @@
+"""@file
+@brief Tests of the chart date validation.
+"""
+
+from datetime import date
+
+import pytest
+
+from musical_time_machine.domain.chart_date import parse_chart_date
+from musical_time_machine.domain.errors import InvalidChartDateError
+
+
+def test_parse_chart_date_returns_date_for_valid_text() -> None:
+    assert parse_chart_date("2026-04-18") == date(2026, 4, 18)
+
+
+def test_parse_chart_date_accepts_leap_day_and_surrounding_whitespace() -> None:
+    assert parse_chart_date(" 2024-02-29\n") == date(2024, 2, 29)
+
+
+@pytest.mark.parametrize(
+    "text",
+    ["18-04-2026", "2026/04/18", "2026-4-8", "yesterday", "", "   "],
+)
+def test_parse_chart_date_rejects_bad_format(text: str) -> None:
+    with pytest.raises(InvalidChartDateError):
+        parse_chart_date(text)
+
+
+@pytest.mark.parametrize("text", ["2026-02-30", "2025-02-29", "2026-13-01"])
+def test_parse_chart_date_rejects_impossible_date(text: str) -> None:
+    with pytest.raises(InvalidChartDateError):
+        parse_chart_date(text)
+
+
+def test_parse_chart_date_message_names_the_input_and_format() -> None:
+    with pytest.raises(InvalidChartDateError, match=r"'nope'.*YYYY-MM-DD"):
+        parse_chart_date("nope")

tests/unit/infrastructure/test_bakeboard_parser.py

@@ -0,0 +1,45 @@
+"""@file
+@brief Tests of the Bakeboard page parser.
+"""
+
+import pytest
+
+from musical_time_machine.constants import CHART_SIZE
+from musical_time_machine.domain.errors import ChartParseError
+from musical_time_machine.infrastructure.bakeboard import parse_chart
+
+
+def test_parse_chart_returns_one_hundred_songs_from_fixture(chart_html: str) -> None:
+    songs = parse_chart(chart_html)
+
+    assert len(songs) == CHART_SIZE
+    assert all(song.title and song.artist for song in songs)
+
+
+def test_parse_chart_strips_whitespace_and_keeps_order(chart_html: str) -> None:
+    first = parse_chart(chart_html)[0]
+
+    assert first.title == "Choosin' Texas"
+    assert first.artist == "Ella Langley"
+
+
+def test_parse_chart_raises_for_page_without_songs() -> None:
+    with pytest.raises(ChartParseError):
+        parse_chart("<html><body><p>nothing</p></body></html>")
+
+
+def test_parse_chart_raises_for_empty_text() -> None:
+    with pytest.raises(ChartParseError):
+        parse_chart("")
+
+
+def test_parse_chart_skips_row_without_artist() -> None:
+    html = (
+        '<div class="chart-entry"><h3 class="chart-entry__title">Lonely</h3></div>'
+        '<div class="chart-entry"><h3 class="chart-entry__title"> A </h3>'
+        '<span class="chart-entry__artist"> B </span></div>'
+    )
+
+    songs = parse_chart(html)
+
+    assert [(s.title, s.artist) for s in songs] == [("A", "B")]

tests/unit/presentation/test_cli.py

@@ -0,0 +1,59 @@
+"""@file
+@brief Tests of the command line with a fake source and injected input and output.
+"""
+
+from conftest import FakeChartSource
+
+from musical_time_machine.constants import CHART_SIZE, DATE_PROMPT
+from musical_time_machine.domain.errors import ChartParseError, ChartUnavailableError
+from musical_time_machine.domain.song import Song
+from musical_time_machine.presentation.cli import main
+
+
+def _run(answer: str, source: FakeChartSource) -> tuple[int, list[str], list[str]]:
+    prompts: list[str] = []
+    lines: list[str] = []
+
+    def read(prompt: str) -> str:
+        prompts.append(prompt)
+        return answer
+
+    code = main([], source=source, read=read, write=lines.append)
+    return code, lines, prompts
+
+
+def test_main_prints_numbered_songs_and_returns_zero() -> None:
+    songs = [Song(f"Title {n}", f"Artist {n}") for n in range(1, CHART_SIZE + 1)]
+
+    code, lines, prompts = _run("2026-04-18", FakeChartSource(songs))
+
+    assert code == 0
+    assert prompts == [DATE_PROMPT]
+    assert len(lines) == CHART_SIZE
+    assert lines[0] == "1. Title 1 - Artist 1"
+    assert lines[-1] == "100. Title 100 - Artist 100"
+
+
+def test_main_returns_one_with_message_for_invalid_date() -> None:
+    source = FakeChartSource([Song("x", "y")])
+
+    code, lines, _ = _run("18/04/2026", source)
+
+    assert code == 1
+    assert len(lines) == 1
+    assert "YYYY-MM-DD" in lines[0]
+    assert source.requested == []
+
+
+def test_main_returns_one_when_chart_unavailable() -> None:
+    code, lines, _ = _run("2026-04-18", FakeChartSource(error=ChartUnavailableError("404")))
+
+    assert code == 1
+    assert lines == ["404"]
+
+
+def test_main_returns_one_when_chart_has_no_songs() -> None:
+    code, lines, _ = _run("2026-04-18", FakeChartSource(error=ChartParseError("empty")))
+
+    assert code == 1
+    assert lines == ["empty"]