Sorry if I am a bit late to the party. I am a student right now and this is one of the issues that's freaking me out about working in the industry. I'm genuinel

Sorry if I am a bit late to the party. I am a student right now and this is one of the issues that's freaking me out about working in the industry. I'm genuinely scared my code is not up to par, have no ideas what security issues I should take care of to start with and also how the hell am I supposed to cover all test cases with TDD? I am alright with following design patterns and ensuring clean documented code but am always under the impression I can do better. If anyone has any insights, would be really grateful, especially when it somes to security.