test(api): end-to-end contextual ranking test for /api/radio

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/api/radio_test.go

@@ -6,6 +6,8 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"testing"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/recommendation"
 )
 
 func callRadio(h *handlers, user interface{}, query string) *httptest.ResponseRecorder {
@@ -128,3 +130,74 @@ func TestHandleRadio_LimitClampedToMax(t *testing.T) {
 		t.Errorf("len = %d, want 6", len(resp.Tracks))
 	}
 }
+
+func TestHandleRadio_ContextualMatch_BoostsRankingOverControl(t *testing.T) {
+	h, pool := testHandlers(t)
+	truncateLibrary(t, pool)
+	user := seedUser(t, pool, "alice", "x", false)
+
+	// Two artists in distinct genres, so we can construct a "rock vibe" session
+	// and a contextual match.
+	rockArtist := seedArtist(t, pool, "RockArtist")
+	rockAlbum := seedAlbum(t, pool, rockArtist.ID, "RockAlbum", 2020)
+	jazzArtist := seedArtist(t, pool, "JazzArtist")
+	jazzAlbum := seedAlbum(t, pool, jazzArtist.ID, "JazzAlbum", 2020)
+
+	// Seed track is unrelated to both (don't want it to dominate scoring).
+	popArtist := seedArtist(t, pool, "PopArtist")
+	popAlbum := seedAlbum(t, pool, popArtist.ID, "PopAlbum", 2020)
+	seed := seedTrack(t, pool, popAlbum.ID, popArtist.ID, "Seed", 1, 100_000)
+
+	// Target: a rock track. Control: a jazz track. Both will be scored.
+	target := seedTrackWithGenre(t, pool, rockAlbum.ID, rockArtist.ID, "Target", 1, 100_000, "rock")
+	control := seedTrackWithGenre(t, pool, jazzAlbum.ID, jazzArtist.ID, "Control", 1, 100_000, "jazz")
+	_ = control // present in DB; we look it up by title in the response
+
+	// Build the user's "rock vibe" current context: insert an open play_session
+	// with a play_event whose session_vector_at_play matches the rock vibe.
+	rockVec := recommendation.SessionVector{
+		Artists: []string{rockArtist.ID.String()},
+		Tags:    map[string]int{"rock": 3},
+	}
+	rockVecJSON, err := json.Marshal(rockVec)
+	if err != nil {
+		t.Fatalf("marshal rockVec: %v", err)
+	}
+	insertOpenSessionWithVector(t, pool, user.ID, rockArtist.ID, rockVecJSON)
+
+	// Insert a contextual_like on the target track whose stored vector matches
+	// the rock vibe. Direct DB insert — we want full control over the vector
+	// for this test.
+	if _, err := pool.Exec(context.Background(),
+		`INSERT INTO contextual_likes (user_id, track_id, session_vector) VALUES ($1, $2, $3)`,
+		user.ID, target.ID, rockVecJSON); err != nil {
+		t.Fatalf("insert contextual_like: %v", err)
+	}
+
+	// Request radio. The deterministic RNG (rng=0.5 → jitter contribution = 0)
+	// means rankings are reproducible for this test.
+	w := callRadio(h, user, "seed_track="+uuidToString(seed.ID))
+	if w.Code != http.StatusOK {
+		t.Fatalf("status = %d body=%s", w.Code, w.Body.String())
+	}
+	var resp RadioResponse
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+
+	targetIdx, controlIdx := -1, -1
+	for i, tr := range resp.Tracks {
+		if tr.Title == "Target" {
+			targetIdx = i
+		}
+		if tr.Title == "Control" {
+			controlIdx = i
+		}
+	}
+	if targetIdx == -1 || controlIdx == -1 {
+		t.Fatalf("target=%d control=%d, expected both present (resp.Tracks=%v)", targetIdx, controlIdx, resp.Tracks)
+	}
+	if targetIdx >= controlIdx {
+		t.Errorf("target ranked at %d, control at %d: contextual match should put target above control", targetIdx, controlIdx)
+	}
+}