Web application testing in simple terms is checking your web application for potential bugs before its made live or before code is moved into the production environment.
During this stage issues such as that of web application security, the functioning of the site, its access to handicapped as well as regular users and its ability to handle traffic is checked.

Web Application Testing Checklist:
1) Functionality Testing
2) Usability testing
3) Interface testing
4) Compatibility testing
5) Performance testing
6) Security testing
7) Database Testing
8) Crowd Testing


1) Functionality Testing:
Functionality Testing : This is used to check of your product is as per the specifications you intended for it as well as the functional requirements you charted out for it in your developmental documentation.Testing Activities Included:
Test all links in your webpages are working correctly and make sure there are no broken links. Links to be checked will include -
Outgoing links
Internal links
Anchor Links
MailTo Links

2) Usability Testing:

Test for navigation:
Navigation means how the user surfs the web pages, different controls like buttons, boxes or how user using the links on the pages to surf different pages.
Usability testing includes:
Web site should be easy to use. Instructions should be provided clearly. Check if the provided instructions are correct means whether they satisfy purpose.
Main menu should be provided on each page. It should be consistent.

3) Interface Testing:
The main interfaces are:
Web server and application server interface
Application server and Database server interface.

Check if all the interactions between these servers are executed properly. Errors are handled properly. If database or web server returns any error message for any query by application server then application server should catch and display these error messages appropriately to users. Check what happens if user interrupts any transaction in-between? Check what happens if connection to web server is reset in between?

4) Compatibility Testing:
Compatibility of your web site is very important testing aspect. See which compatibility test to be executed:
Browser compatibility
Operating system compatibility
Mobile browsing
Printing options

5) Performance testing:
Web application should sustain to heavy load. Web performance testing should include:
Web Load Testing
Web Stress Testing

6) Security Testing:

Following are some test cases for web security testing:

• Test by pasting internal url directly into browser address bar without login. Internal pages should not open.
• If you are logged in using username and password and browsing internal pages then try changing url options directly. I.e. If you are checking some publisher site statistics with publisher site ID= 123. Try directly changing the url site ID parameter to different site ID which is not related to logged in user. Access should denied for this user to view others stats.
• Try some invalid inputs in input fields like login username, password, input text boxes. Check the system reaction on all invalid inputs.
• Web directories or files should not be accessible directly unless given download option.
• Test the CAPTCHA for automates scripts logins.
• Test if SSL is used for security measures. If used proper message should get displayed when user switch from non-secure http:// pages to secure https:// pages and vice versa.
• All transactions, error messages, security breach attempts should get logged in log files somewhere on web server.

7) Database Testing:
Database is one critical component of your web application and stress must be laid to test it thoroughly. Testing activities will include-

• Test if any errors are shown while executing queries
• Data Integrity is maintained while creating , updating or deleting data in database.
• Check response time of queries and fine tune them if necessary.
• Test data retrieved from your database is shown accurately in your web application

8)Crowd Testing:
You will select a large number of people (crowd) to execute tests which otherwise would have been executed a select group of people in the company. Crowdsourced testing is an interesting and upcoming concept and helps unravel many a unnoticed defects.

Article Source: http://www.softwaretestinghelp.com/web-application-testing/
Article source: http://www.guru99.com/web-application-testing.html