A step toward what? Nuclear weapons, the test ban, and a world without nuclear testing

Historically, nuclear-explosive testing was not required to develop simple, reliable, gun-type nuclear weapons with highly enriched uranium as the chain-reacting material. Testing may now not be required to build basic implosion weapons using plutonium. This suggests that, even if no state had ever conducted a nuclear test, a nuclear-armed world could still have emerged, but probably without thermonuclear weapons. The examples of the United States, Russia, the United Kingdom, France, and Pakistan suggest that, despite the twenty-year-old Comprehensive Nuclear-Test-Ban Treaty (CTBT), nuclear-weapon states with very different testing legacies expect to continue developing, and in some cases deploying, new nuclear weapons. The entry into force of the CTBT might not significantly constrain nuclear-weapons development for any state, and a worthwhile goal now may be to focus on other agreements to restrict nuclear weapon activities, in particular an agreement to ban nuclear weapons.