internal/recommendation/candidate_tags_integration_test.go

@@ -399,23 +399,57 @@ func TestSuggestArtists_UntaggedCandidateSurvivesAlongsideTagged(t *testing.T) {
 	seedCandidateTag(t, pool, "match", "shoegaze", 1.0)
 	// "loud" is deliberately left with NO cached tags at all.
 
-	out, err := SuggestArtists(context.Background(), pool, user.ID, 30, 12, 1.0)
+	// Compared against the same request with the term disabled, rather than
+	// against a literal. The pool score is signal-weighted by the seed query
+	// (ln(1+signal) x similarity), so hardcoding a number here would assert
+	// against the seeding maths — a different layer — and break whenever that
+	// changes. The property under test is only that the blend leaves an
+	// untagged candidate alone.
+	blended, err := SuggestArtists(context.Background(), pool, user.ID, 30, 12, 1.0)
 	if err != nil {
-		t.Fatalf("SuggestArtists: %v", err)
+		t.Fatalf("SuggestArtists(blended): %v", err)
 	}
-	if len(out) != 2 {
-		t.Fatalf("len = %d, want 2 — the untagged candidate must still appear", len(out))
+	baseline, err := SuggestArtists(context.Background(), pool, user.ID, 30, 12, 0)
+	if err != nil {
+		t.Fatalf("SuggestArtists(baseline): %v", err)
 	}
-	var loud *ArtistSuggestion
-	for i := range out {
-		if out[i].MBID == "loud" {
-			loud = &out[i]
+	if len(blended) != 2 {
+		t.Fatalf("len = %d, want 2 — the untagged candidate must still appear", len(blended))
+	}
+
+	scoreOf := func(out []ArtistSuggestion, mbid string) (float64, bool) {
+		for _, s := range out {
+			if s.MBID == mbid {
+				return s.Score, true
 			}
 		}
-	if loud == nil {
-		t.Fatal("untagged candidate vanished from the deck")
+		return 0, false
 	}
-	if loud.Score != 0.9 {
-		t.Errorf("untagged score = %v, want 0.9 unchanged", loud.Score)
+	want, ok := scoreOf(baseline, "loud")
+	if !ok {
+		t.Fatal("untagged candidate missing from the baseline deck")
+	}
+	got, ok := scoreOf(blended, "loud")
+	if !ok {
+		t.Fatal("untagged candidate vanished once the tag term was enabled")
+	}
+	if got != want {
+		t.Errorf("untagged score = %v, want %v (identical to the term-disabled run)", got, want)
+	}
+	// Sanity: the tagged candidate DID move, so the comparison above is
+	// meaningful rather than both runs being trivially identical.
+	if tagged, _ := scoreOf(blended, "match"); tagged == mustScore(t, baseline, "match") {
+		t.Error("the tagged candidate's score did not change — the term did nothing")
 	}
 }
+
+func mustScore(t *testing.T, out []ArtistSuggestion, mbid string) float64 {
+	t.Helper()
+	for _, s := range out {
+		if s.MBID == mbid {
+			return s.Score
+		}
+	}
+	t.Fatalf("no candidate %q in %v", mbid, out)
+	return 0
+}