In parallel run of software testing
In parallel run of software testing Only physical system runs.
In software testing, verifying compatibility of the newly developed system with the old system is done through "parallel testing." In parallel testing, tester runs two different versions of software concurrently with same input. ... It ensures that the new system is capable enough to run the software efficiently.
Parallel testing means testing multiple applications or subcomponents of one application concurrently to reduce the test time. Parallel tests consist of two or more parts (projects or project suites) that check different parts or functional characteristics of an application.
TestNG provides multiple ways to execute tests in separate threads. In testng.xml, if we set 'parallel' attribute on the tag to 'tests', testNG will run all the '@Test' methods in tag in the same thread, but each tag will be in a separate thread. This helps us to run test methods / classes / tests in parallel.