A nuclear test is an experiment conducted to evaluate the performance and effects of nuclear weapons. These tests can involve detonating a nuclear device above ground, underground, or underwater. The primary purpose is to gather data on the weapon's yield, efficiency, and impact on the environment. Countries that possess nuclear weapons, such as the United States, Russia, and North Korea, have conducted various nuclear tests throughout history. These tests are often controversial due to their potential to cause environmental damage and escalate global tensions, leading to international treaties aimed at limiting or banning such activities, like the Comprehensive Nuclear-Test-Ban Treaty.