A system and associated method for asynchronous code testing in an Integrated Development Environment (IDE). The IDE has components of a source code editor, an impact analyzer, a test case launcher, a graphical user interface (GUI), and a database. All components run concurrently for asynchronous and real-time code editing. Upon modification of a code block of an input code, a test case is automatically generated and a launching priority is calculated based on the relationship between the modified code block and each code block affected by the modification. Generated test cases are automatically run by the test case launcher or manually selected by the user to produce a test run result.