defer db.mu.Unlock()
	return len(db.freeConn)
}

func (db *DB) numOpenConns() int {
	db.mu.Lock()
	defer db.mu.Unlock()
	return db.numOpen
}

// clearAllConns closes all connections in db.
func (db *DB) clearAllConns(t *testing.T) {
	db.SetMaxIdleConns(0)

	if g, w := db.numFreeConns(), 0; g != w {
		t.Errorf("free conns = %d; want %d", g, w)
	}

	if n := db.numDepsPoll(t, 0); n > 0 {