A method of leak testing a flexible expandable bag having at least one port and at least one flexible wall, the method comprising: (a) filling the flexible bag with gas flowing through the at least one port such that the flexible bag expands, wherein filling the flexible bag includes measuring a flow rate of the gas into the flexible bag while maintaining a constant pressure of the gas in the flexible bag； (b) measuring displacement of the flexible wall； and, (c) determining whether a leak is present.
