My question so general, but I think the answer will be specific.
All I want to know is:
Is there a way or steps or mechanism to test the application (web application) in a professional way?
Many times when I finish developing and try my application, testing it with dummy data several times, and when I think every thing is okay and I think I have covered all possible scenarios, I find I forgot important issues, or others tell me they found problems in my application.
How do I overcome this problem, and save my time?
Good links:
As a proffesional tester my suggestion is that you should have a healthy mix of automated and manual testing.
AUTOMATED TESTING
Unit Testing
Use NUnit to test your classes, functions and interaction between them.
http://www.nunit.org/index.php
Automated Functional Testing
If it’s possible you should automate a lot of the functional testing. Some frame works have functional testing built into them. Otherwise you have to use a tool for it. If you are developing web sites/applications you might want to look at Selenium.
http://www.peterkrantz.com/2005/selenium-for-aspnet/
Continuous Integration
Use CI to make sure all your automated tests run every time someone in your team makes a commit to the project.
http://martinfowler.com/articles/continuousIntegration.html
MANUAL TESTING
As much as I love automated testing it is, IMHO, not a substitute for manual testing. The main reason being that an automated can only do what it is told and only verify what it has been informed to view as pass/fail. A human can use it’s intelligence to find faults and raise questions that appear while testing something else.
ET is a very low cost and effective way to find defects in a project. It take advantage of the intelligence of a human being and a teaches the testers/developers more about the project than any other testing technique i know of. Doing an ET session aimed at every feature deployed in the test environment is not only an effective way to find problems fast, but also a good way to learn and fun!
http://www.satisfice.com/articles/et-article.pdf