What is software testing and why it is used?

Software testing is used to  error detection.

Testing software is operating the software under controlled conditions.

1.       Verification

2.      Validation

3.      Error Detection

1.      Verification:

Are we building the system right?

Verification is the checking or testing of items, including software, for conformance and consistency by evaluating the results against pre-specified requirements.

Example : Login to Gmail account.

2.      Validation:

Are we building the right system?

That is the process of checking that what has been specified is what the user actually wanted. 

The validation will be done when the verification is down .It may not occur in every process.

3.      Error Detection:

Testing should intentionally attempt to make things go wrong to determine if things happen when they shouldn’t or things don’t happen when they should.