Batteries tend to fail in extreme cold or extreme hot weather. I have also seen many batteries that will start the car but fail testing. Sometimes we will see a vehicle with too small a battery installed. It’s no different than having a weak battery. A weak battery may get you by until you leave the lights on or your starter gets weak too. Then you are stranded.
Inspect your battery when you check your oil. The battery should be clean and the sides of the body should be straight with no bowing. The battery should fit the mounting area closely. If you can see extra space in the battery tray area where the battery sits, it is probably not the correct battery. The battery should also be mounted firmly to the battery tray. A loose battery can damage other components or move out of place and create an alternate path for current flow draining the battery. I have even seen rooster-tails of sparks flying when a loose battery made contact with the body as the car made a turn!!! Look for white powder on the mounting terminals. White powder is corrosion. Corrosion can eat the terminals until they break and loose contact leading to a no start. Corrosion can also drain the battery by creating an electronic path from the positive terminal to any ground source. Most batteries are dated. If your battery is more than five years old you should have it tested.
If you do not see your battery under the hood, it may be in the trunk or under the rear seat. These are no different than underhood mounted batteries. Vehicle manufacturers move the battery for better weight distribution and better handling.
There are two types of battery tests. Carbon pile load testing and electronic load testing. I have seen batteries pass one test and fail the other.