test: add tests for mergeEpisodes capping and cache validation

internal/episodes/service/service_test.go

@@ -9,13 +9,13 @@ import (
 
 func TestMergeEpisodesUsesUnionAndSynthesizesProviderOnlyEntries(t *testing.T) {
 	episodes := mergeEpisodes([]jikan.Episode{
-		{MalID: 1, Title: "Start"},
+		{MalID: 101, Episode: "1", Title: "Start"},
-		{MalID: 2, Title: "Second", Filler: true},
+		{MalID: 102, Episode: "2", Title: "Second", Filler: true},
-		{MalID: 5, Title: "Future", Recap: true},
+		{MalID: 105, Episode: "5", Title: "Future", Recap: true},
 	}, domain.EpisodeAvailability{
 		Sub: []int{1, 2, 3, 6},
 		Dub: []int{1, 2, 3},
-	})
+	}, 0)
 
 	if len(episodes) != 5 {
 		t.Fatalf("len(episodes) = %d, want 5", len(episodes))
@@ -28,6 +28,64 @@ func TestMergeEpisodesUsesUnionAndSynthesizesProviderOnlyEntries(t *testing.T) {
 	assertEpisode(t, episodes[4], 6, "Episode 6", true, false, true, false, false)
 }
 
+func TestMergeEpisodesIgnoresInvalidJikanEpisodeNumbers(t *testing.T) {
+	episodes := mergeEpisodes([]jikan.Episode{
+		{MalID: 201, Episode: "", Title: "Missing"},
+		{MalID: 202, Episode: "Preview", Title: "Preview"},
+		{MalID: 203, Episode: "0", Title: "Zero"},
+	}, domain.EpisodeAvailability{}, 0)
+
+	if len(episodes) != 3 {
+		t.Fatalf("len(episodes) = %d, want 3", len(episodes))
+	}
+
+	assertEpisode(t, episodes[0], 1, "Missing", false, false, false, false, false)
+	assertEpisode(t, episodes[1], 2, "Preview", false, false, false, false, false)
+	assertEpisode(t, episodes[2], 3, "Zero", false, false, false, false, false)
+}
+
+func TestMergeEpisodesCapsMalformedJikanListsToDeclaredEpisodeCount(t *testing.T) {
+	episodes := mergeEpisodes([]jikan.Episode{
+		{MalID: 301, Episode: "", Title: "Rimuru's Busy Life"},
+		{MalID: 302, Episode: "", Title: "Trade with the Animal Kingdom"},
+		{MalID: 303, Episode: "", Title: "Paradise, Once More"},
+		{MalID: 304, Episode: "", Title: "The Scheming Kingdom of Falmuth"},
+		{MalID: 305, Episode: "", Title: "Prelude to the Disaster"},
+		{MalID: 306, Episode: "", Title: "The Beauty Makes Her Move"},
+		{MalID: 307, Episode: "", Title: "Despair"},
+		{MalID: 308, Episode: "", Title: "Hope"},
+		{MalID: 309, Episode: "", Title: "Putting Everything on the Line"},
+		{MalID: 310, Episode: "", Title: "Megiddo"},
+		{MalID: 311, Episode: "", Title: "Birth of a Demon Lord"},
+		{MalID: 312, Episode: "", Title: "The One Unleashed"},
+		{MalID: 313, Episode: "", Title: "The Visitors"},
+	}, domain.EpisodeAvailability{
+		Sub: []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13},
+		Dub: []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13},
+	}, 12)
+
+	if len(episodes) != 12 {
+		t.Fatalf("len(episodes) = %d, want 12", len(episodes))
+	}
+
+	assertEpisode(t, episodes[0], 1, "Rimuru's Busy Life", true, true, false, false, false)
+	assertEpisode(t, episodes[11], 12, "The One Unleashed", true, true, false, false, false)
+}
+
+func TestIsCanonicalEpisodePayloadValidRejectsOverflowingCachedPayload(t *testing.T) {
+	payload := domain.CanonicalEpisodeList{
+		Episodes: []domain.CanonicalEpisode{
+			{Number: 1, Title: "Episode 1"},
+			{Number: 2, Title: "Episode 2"},
+			{Number: 13, Title: "Episode 13"},
+		},
+	}
+
+	if isCanonicalEpisodePayloadValid(payload, 12) {
+		t.Fatal("expected cached payload to be rejected")
+	}
+}
+
 func TestNextBroadcastAfterUsesJikanTimezone(t *testing.T) {
 	anime := domain.Anime{Anime: jikan.Anime{MalID: 1}}
 	anime.Broadcast.Day = "Saturdays"