Rigorous (adjective)

1. Demanding strict attention to rules and procedures.
2. Having a severe or demanding attitude or approach.
3. Carrying out systematic and thorough analysis or investigation.

Origin:

Late middle english (in the sense 'stiff, rigid'): from latin rigorus, from rigor 'stiffness, severity'. the current sense dates from the early 17th century.

Examples:

1. The teacher has a rigorous grading policy.
2. The interview process was rigorous and lasted several hours.
3. The scientist underwent a rigorous experimentation before publishing the results.
4. The new software underwent rigorous testing before being released to the public.
5. The athlete followed a rigorous training regimen to prepare for the competition.