diff --git a/bouncer/phase07_coverage_test.go b/bouncer/phase07_coverage_test.go
new file mode 100644
index 0000000..f005fe6
--- /dev/null
+++ b/bouncer/phase07_coverage_test.go
@@ -0,0 +1,115 @@
+package bouncer
+
+import (
+	"context"
+	"database/sql"
+	"sync"
+	"testing"
+	"time"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+	"github.com/testcontainers/testcontainers-go"
+	"github.com/testcontainers/testcontainers-go/modules/postgres"
+)
+
+func TestMintRefreshBlacklistRoundTrip(t *testing.T) {
+	const secret = "summercms-test-only-hs256-secret"
+	bl := NewMemoryBlacklist()
+	token, jti, err := Mint(secret, "7", "http://example.com/_user/api/v1/login", time.Hour)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sub, err := Verify(token, secret)
+	if err != nil || sub != "7" {
+		t.Fatalf("verify %q %v", sub, err)
+	}
+	next, err := Refresh(secret, token, 2*time.Hour, bl, 0, "http://example.com/_user/api/v1/refresh")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := Verify(next, secret); err != nil {
+		t.Fatal(err)
+	}
+	blocked, err := bl.IsBlacklisted(context.Background(), jti)
+	if err != nil || !blocked {
+		t.Fatalf("old jti blacklisted=%t err=%v", blocked, err)
+	}
+	if _, err := Refresh(secret, token, 2*time.Hour, bl, 0, "http://example.com/_user/api/v1/refresh"); err == nil {
+		t.Fatal("blacklisted token refreshed")
+	}
+}
+
+func TestMemoryBlacklistConcurrent(t *testing.T) {
+	bl := NewMemoryBlacklist()
+	var wg sync.WaitGroup
+	for i := 0; i < 8; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			now := time.Now()
+			if err := bl.Add(context.Background(), "jti", now.Add(time.Hour), now.Add(-time.Second)); err != nil {
+				t.Error(err)
+				return
+			}
+			if _, err := bl.IsBlacklisted(context.Background(), "jti"); err != nil {
+				t.Error(err)
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+func TestPostgresBlacklistConcurrent(t *testing.T) {
+	if testing.Short() {
+		t.Skip("postgres blacklist concurrency needs testcontainers")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+	ctr, err := postgres.Run(ctx, "postgres:16-alpine",
+		postgres.WithDatabase("bl"),
+		postgres.WithUsername("bl"),
+		postgres.WithPassword("bl"),
+		postgres.BasicWaitStrategies(),
+		testcontainers.WithEnv(map[string]string{
+			"POSTGRES_INITDB_ARGS": "--locale-provider=icu --icu-locale=pl-PL --encoding=UTF8",
+		}),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = ctr.Terminate(context.Background()) })
+	dsn, err := ctr.ConnectionString(ctx, "sslmode=disable")
+	if err != nil {
+		t.Fatal(err)
+	}
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = db.Close() })
+	if _, err := db.ExecContext(ctx, `CREATE TABLE jwt_blacklist (
+		jti text PRIMARY KEY,
+		expires_at timestamptz NOT NULL,
+		valid_until timestamptz NOT NULL
+	)`); err != nil {
+		t.Fatal(err)
+	}
+	bl := NewPostgresBlacklist(db, "jwt_blacklist")
+	var wg sync.WaitGroup
+	for i := 0; i < 8; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			now := time.Now()
+			if err := bl.Add(ctx, "shared", now.Add(time.Hour), now.Add(-time.Second)); err != nil {
+				t.Error(err)
+				return
+			}
+			blocked, err := bl.IsBlacklisted(ctx, "shared")
+			if err != nil || !blocked {
+				t.Errorf("blocked=%t err=%v", blocked, err)
+			}
+		}()
+	}
+	wg.Wait()
+}