MIL-003: Step 2 - New flash cards

Review record RC-025 (Go, autonomous mode, not independent).

Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4
Task: MIL-003#5

tests/unit/application/test_open_study_session.py

@@ -0,0 +1,44 @@
+"""Tests of the open_study_session use case."""
+
+from collections.abc import Sequence
+
+import pytest
+
+from flash_card.application.dto.card_dto import CardDto
+from flash_card.application.use_cases.open_study_session import open_study_session
+from flash_card.domain.entities.card import Card
+from flash_card.domain.entities.vocabulary import Vocabulary
+from flash_card.domain.errors.vocabulary_errors import VocabularyNotFoundError
+from flash_card.domain.value_objects.language_pair import LanguagePair
+
+
+class _FakeRepository:
+    def __init__(self, vocabulary: Vocabulary) -> None:
+        self._vocabulary = vocabulary
+
+    def load(self) -> Vocabulary:
+        return self._vocabulary
+
+
+class _MissingRepository:
+    def load(self) -> Vocabulary:
+        raise VocabularyNotFoundError("missing")
+
+
+def _first(cards: Sequence[Card]) -> Card:
+    return cards[0]
+
+
+def test_open_study_session_builds_session_over_all_cards() -> None:
+    cards = (Card("aku", "mig"), Card("kau", "du"))
+    repository = _FakeRepository(Vocabulary(LanguagePair("ms", "da"), cards))
+
+    session = open_study_session(repository, _first)
+
+    assert session.remaining == 2
+    assert session.next_card() == CardDto("aku", "mig", "ms", "da")
+
+
+def test_open_study_session_propagates_repository_error() -> None:
+    with pytest.raises(VocabularyNotFoundError):
+        open_study_session(_MissingRepository(), _first)