feat: derive authoritative ranked tiers

server/domain/tier_test.go

@@ -0,0 +1,56 @@
+package domain
+
+import "testing"
+
+func testTierPolicy(t *testing.T) TierPolicy {
+	t.Helper()
+	policy, err := NewTierPolicy([]TierBand{
+		{Tier: RankTierBronze, MinRating: 0},
+		{Tier: RankTierSilver, MinRating: 1200},
+		{Tier: RankTierGold, MinRating: 1500},
+		{Tier: RankTierPlatinum, MinRating: 1800},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return policy
+}
+
+func TestRankedTierUsesAuthoritativeBandsAndExactBoundaries(t *testing.T) {
+	policy := testTierPolicy(t)
+	for _, test := range []struct {
+		rating float64
+		games  int
+		want   RankTier
+	}{
+		{rating: 2000, games: 0, want: RankTierProvisional},
+		{rating: 1199.99, games: 10, want: RankTierBronze},
+		{rating: 1200, games: 10, want: RankTierSilver},
+		{rating: 1499.99, games: 10, want: RankTierSilver},
+		{rating: 1500, games: 10, want: RankTierGold},
+		{rating: 1800, games: 10, want: RankTierPlatinum},
+	} {
+		got, err := RankedTier(RankedProfile{Rating: Rating{Value: test.rating}, RankedGames: test.games}, policy)
+		if err != nil || got != test.want {
+			t.Errorf("rating %.2f games %d = %s, err=%v; want %s", test.rating, test.games, got, err, test.want)
+		}
+	}
+}
+
+func TestTierPolicyRejectsUnorderedOrUnboundedConfiguration(t *testing.T) {
+	for _, bands := range [][]TierBand{
+		{},
+		{{Tier: RankTierBronze, MinRating: 1}},
+		{{Tier: RankTierBronze, MinRating: 0}, {Tier: RankTierSilver, MinRating: 0}},
+		{{Tier: RankTierBronze, MinRating: 0}, {Tier: RankTierSilver, MinRating: -1}},
+		{{Tier: RankTierBronze, MinRating: 0}, {Tier: RankTier(""), MinRating: 1200}},
+	} {
+		if _, err := NewTierPolicy(bands); err == nil {
+			t.Errorf("invalid tier policy accepted: %+v", bands)
+		}
+	}
+	policy := testTierPolicy(t)
+	if _, err := RankedTier(RankedProfile{Rating: Rating{Value: 1500}, RankedGames: -1}, policy); err == nil {
+		t.Fatal("negative ranked games accepted")
+	}
+}