Listener Mike has a Testing Parable

A testing parable:

There once was a plumber who had a magnificent testing machine. It could test all sorts of pipes under pressure. It could test long pipes, short pipes, wide pipes, narrow pipes, PVC pipes, lead pipes... you get the idea. Since the testing machine made it so simple to test pipes, the plumber used it with every pipe that he installed, no matter how short the distance nor how low the pressure. Soon afterward, he was awarded a contract to install the plumbing for a large building. 

He was able to make the plumbing system incredibly simple; there was no need for pressure gauges, shut-off valves, or check valves, for all of his pipes had been tested to be correct and nothing could go wrong. 

When the job was finished and the connection to the main was opened, the plumber was dismayed to discover that the plumbing system failed. Although none of the pipes burst under pressure, there were many large leaks at the joints.