What is the difference between smoke testing, critical path, and regression testing?

Smoke Testing: Checking the basic, critically important functions of the system after build or deployment to ensure its fundamental operability. Performed quickly and determines whether further detailed testing is possible.

Critical Path Testing: End-to-end scenario testing representing the most important and frequently used business processes. Conducted to verify the integrity and functionality of user flow processes.

Regression Testing: Testing to confirm that new code changes (fixes, new features) have not broken existing system functionality and have not introduced new defects in previously working parts. Performed after each change or build.

Characteristic	Smoke Testing	Critical Path Testing	Regression Testing
Purpose	Checking basic operability after build.	Checking end-to-end business processes.	Ensuring no negative impact of changes on the system.
Scope	Small, main functionalities.	Main, frequently used user flows.	Extensive, covering all previously working parts.
When performed	After each build/deployment.	At various testing stages, including after major releases.	After each code change, bug fix, new feature.
Speed	Fast.	Depends on the complexity of the path.	Can be lengthy (often automated).
Detail	Low, superficial.	High for the selected path.	High.
Main focus	Stability and readiness for further testing.	Correctness of key scenario execution.	Absence of introduced defects.