If you are doing supply line piping for new construction, and you soldered copper pipes for hot water, is it enough to test the joints with cold water before you close the wall up or back fill the floor?

In my case, I have finished soldering the cold side and hot side. The water heater hasn't been installed yet so I have no means to test with hot water. So I went to the laundry room where I have a cold valve and a hot valve, and connected the two with a washing machine hose, turned both valves OPEN. This will send the cold water into the hot water lines. No leak.

Is this enough of leak test? Or there may be concerns that when real hot water passes through these lines, the higher temperature may stress the weak joints more?

that is not a concern..

in new construction you would put an air test on it.

Even in hydronic heating, water temps are 190*, way below the melting point of solder, for domestic HW temps are more likely 140* or less. If it doesn't leak cold water it won't leak hot.

Don, I wasn't worried about the solder's melting point, I was thinking along the line of perhaps a "marginal" joint where the solder didn't tin 100% of the interior surfaces, and don't leak with cold water, may possibly leak with hot water when the solder & metal expands and contracts with the hot water flowing through?

Probably not a problem. Just being extra cautious.

Go to You Tube and look for videos that show how to solder. It begins by cleaning the inside of the fitting and the outside of the tubing. Then applying flux on those cleaned surfaces. Then and most critically, apply heat on the tube next to the fitting so it heats up inside the fitting. Here you have to be careful not to over heat as you move the flame back and forth from the tubing to the fitting until you will see smoke from the solder which is a sign that the joint is getting hot enough. The test if it is hot enough is to apply solder and watch it suck into the joint by capillary attraction or action. You should fill it until the joint is full then remove the solder. Make sure you heated all around the joint to be sure that it is tinned as was mentioned above on both surfaces. The video will show you but I recommend watching a few videos and don't over heat because it burns up the flux and prevents a good joint. Remember, you can't solder as long as water is inside the pipe and you must have a valve open so pressure does not build up inside the tubing. Pressure and steam are not your friends. Good luck.

PlumberLoren, thanks for the advice. I have soldered many joints in my DIY projects over the years I just wanted to make sure I stress test this one before I bury and pour concrete over it because its a big deal to access it once its covered.