feat(lobby): start round with selected category

lobby/tests.py

@@ -2,7 +2,7 @@ from django.contrib.auth import get_user_model
 from django.test import TestCase
 from django.urls import reverse
 
-from fupogfakta.models import GameSession, Player
+from fupogfakta.models import Category, GameSession, Player, Question, RoundConfig
 
 User = get_user_model()
 
@@ -81,3 +81,82 @@ class LobbyFlowTests(TestCase):
         payload = response.json()
         self.assertEqual(payload["session"]["players_count"], 2)
         self.assertEqual([p["nickname"] for p in payload["players"]], ["Bo", "Mia"])
+
+
+class StartRoundTests(TestCase):
+    def setUp(self):
+        self.host = User.objects.create_user(username="host", password="secret123")
+        self.other_user = User.objects.create_user(username="other", password="secret123")
+        self.session = GameSession.objects.create(host=self.host, code="ABCD23")
+        self.category = Category.objects.create(name="Historie", slug="historie", is_active=True)
+        Question.objects.create(
+            category=self.category,
+            prompt="Hvilket år faldt muren?",
+            correct_answer="1989",
+            is_active=True,
+        )
+
+    def test_host_can_start_round_with_selected_category(self):
+        self.client.login(username="host", password="secret123")
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": self.category.slug},
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 201)
+        body = response.json()
+        self.assertEqual(body["session"]["status"], GameSession.Status.LIE)
+        self.assertEqual(body["round"]["number"], 1)
+        self.assertEqual(body["round"]["category"]["slug"], self.category.slug)
+
+        self.session.refresh_from_db()
+        self.assertEqual(self.session.status, GameSession.Status.LIE)
+        round_config = RoundConfig.objects.get(session=self.session, number=1)
+        self.assertEqual(round_config.category, self.category)
+
+    def test_start_round_requires_host(self):
+        self.client.login(username="other", password="secret123")
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": self.category.slug},
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 403)
+        self.assertEqual(response.json()["error"], "Only host can start round")
+
+    def test_start_round_requires_existing_active_category_with_questions(self):
+        self.client.login(username="host", password="secret123")
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": "ukendt"},
+            content_type="application/json",
+        )
+        self.assertEqual(response.status_code, 404)
+
+        empty_category = Category.objects.create(name="Sport", slug="sport", is_active=True)
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": empty_category.slug},
+            content_type="application/json",
+        )
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json()["error"], "Category has no active questions")
+
+    def test_start_round_rejects_non_lobby_session(self):
+        self.client.login(username="host", password="secret123")
+        self.session.status = GameSession.Status.GUESS
+        self.session.save(update_fields=["status"])
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": self.category.slug},
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json()["error"], "Round can only be started from lobby")