What is Cookie?
Cookie is small information stored in text file on user’s
hard drive by web server. This information is later used by web browser to
retrieve information from that machine. Generally cookie contains personalized
user data or information that is used to communicate between different web
pages.
Why Cookies are used?
Cookies are nothing but the user’s identity and used to
track where the user navigated throughout the web site pages. The communication
between web browser and web server is stateless.
For example if you are accessing domain
http://www.example.com/1.html then web browser will simply query to example.com
web server for the page 1.html. Next time if you type page as
http://www.example.com/2.html then new request is send to example.com web
server for sending 2.html page and web server don’t know anything about to whom
the previous page 1.html served.
What if you want the previous history of this user
communication with the web server? You need to maintain the user state and
interaction between web browser and web server somewhere. This is where cookie
comes into picture. Cookies serve the purpose of maintaining the user
interactions with web server.
How cookies work?
The HTTP protocol used to exchange information files on the
web is used to maintain the cookies. There are two types of HTTP protocol.
Stateless HTTP and Stateful HTTP protocol. Stateless HTTP protocol does not
keep any record of previously accessed web page history. While Stateful HTTP
protocol do keep some history of previous web browser and web server
interactions and this protocol is used by cookies to maintain the user
interactions.
Whenever user visits the site or page that is using cookie,
small code inside that HTML page (Generally a call to some language script to
write the cookie like cookies in JAVAScript, PHP, Perl) writes a text file on
users machine called cookie.
Here is one example of the code that is used to write cookie
and can be placed inside any HTML page:
Set-Cookie: NAME=VALUE; expires=DATE; path=PATH;
domain=DOMAIN_NAME;
When user visits the same page or domain later time this
cookie is read from disk and used to identify the second visit of the same user
on that domain. Expiration time is set while writing the cookie. This time is
decided by the application that is going to use the cookie.
Generally two types
of cookies are written on user machine.
1) Session cookies: This cookie is active till the browser
that invoked the cookie is open. When we close the browser this session cookie
gets deleted. Some time session of say 20 minutes can be set to expire the
cookie.
2) Persistent cookies: The cookies that are written
permanently on user machine and lasts for months or years.
Where cookies are stored?
When any web page application writes cookie it get saved in
a text file on user hard disk drive. The path where the cookies get stored
depends on the browser. Different browsers store cookie in different paths.
E.g. Internet explorer store cookies on path “C:\Documents and Settings\Default
User\Cookies”
Here the “Default User” can be replaced by the current user
you logged in as. Like “Administrator”, or user name like “Vijay” etc.
The cookie path can be easily found by navigating through
the browser options. In Mozilla Firefox browser you can even see the cookies in
browser options itself. Open the Mozila browser, click on
Tools->Options->Privacy and then “Show cookies” button.
How cookies are stored?
Lets take example of cookie written by rediff.com on Mozilla
Firefox browser:
On Mozilla Firefox browser when you open the page rediff.com
or login to your rediffmail account, a cookie will get written on your Hard
disk. To view this cookie simply click on “Show cookies” button mentioned on
above path. Click on Rediff.com site under this cookie list. You can see
different cookies written by rediff domain with different names.
Site: Rediff.com
Cookie name: RMID
Name: RMID (Name
of the cookie)
Content:
1d11c8ec44bf49e0… (Encrypted content)
Domain:
.rediff.com
Path: / (Any path
after the domain name)
Send For: Any
type of connection
Expires:
Thursday, December 31, 2020 11:59:59 PM
Applications where
cookies can be used:
1) To implement
shopping cart:
Cookies are used for maintaining online ordering system.
Cookies remember what user wants to buy. What if user adds some products in
their shopping cart and if due to some reason user don’t want to buy those
products this time and closes the browser window? When next time same user
visits the purchase page he can see all the products he added in shopping cart
in his last visit.
2) Personalized
sites:
When user visits certain pages they are asked which pages
they don’t want to visit or display. User options are get stored in cookie and
till the user is online, those pages are not shown to him.
3) User tracking:
To track number of unique visitors online at particular
time.
4) Marketing:
Some companies use cookies to display advertisements on user
machines. Cookies control these advertisements. When and which advertisement
should be shown? What is the interest of the user? Which keywords he searches
on the site? All these things can be maintained using cookies.
5) User sessions:
Cookies can track user sessions to particular domain using
user ID and password.
Drawbacks of cookies:
1) Even writing Cookie is a great way to maintain user
interaction, if user has set browser options to warn before writing any cookie
or disabled the cookies completely then site containing cookie will be
completely disabled and can not perform any operation resulting in loss of site
traffic.
2) Too many Cookies:
If you are writing too many cookies on every page navigation
and if user has turned on option to warn before writing cookie, this could turn
away user from your site.
3) Security issues:
Some times users personal information is stored in cookies
and if someone hack the cookie then hacker can get access to your personal
information. Even corrupted cookies can be read by different domains and lead
to security issues.
4) Sensitive
information:
Some sites may write and store your sensitive information in
cookies, which should not be allowed due to privacy concerns.
This should be enough to know what cookies are. If you want
more cookie info see Cookie Central page.
Some Major Test cases for web application cookie testing:
The first obvious test case is to test if your application
is writing cookies properly on disk. You can use the Cookie Tester application
also if you don’t have any web application to test but you want to understand
the cookie concept for testing.
Test cases:
1) As a Cookie privacy policy make sure from your design
documents that no personal or sensitive data is stored in the cookie.
2) If you have no option than saving sensitive data in
cookie make sure data stored in cookie is stored in encrypted format.
3) Make sure that there is no overuse of cookies on your
site under test. Overuse of cookies will annoy users if browser is prompting
for cookies more often and this could result in loss of site traffic and
eventually loss of business.
4) Disable the cookies from your browser settings: If you
are using cookies on your site, your sites major functionality will not work by
disabling the cookies. Then try to access the web site under test. Navigate
through the site. See if appropriate messages are displayed to user like “For
smooth functioning of this site make sure that cookies are enabled on your
browser”. There should not be any page crash due to disabling the cookies.
(Please make sure that you close all browsers, delete all previously written
cookies before performing this test)
5) Accepts/Reject some cookies: The best way to check web
site functionality is, not to accept all cookies. If you are writing 10 cookies
in your web application then randomly accept some cookies say accept 5 and
reject 5 cookies. For executing this test case you can set browser options to
prompt whenever cookie is being written to disk. On this prompt window you can
either accept or reject cookie. Try to access major functionality of web site.
See if pages are getting crashed or data is getting corrupted.
6) Delete cookie: Allow site to write the cookies and then
close all browsers and manually delete all cookies for web site under test.
Access the web pages and check the behavior of the pages.
7) Corrupt the cookies: Corrupting cookie is easy. You know where
cookies are stored. Manually edit the cookie in notepad and change the
parameters to some vague values. Like alter the cookie content, Name of the
cookie or expiry date of the cookie and see the site functionality. In some
cases corrupted cookies allow to read the data inside it for any other domain.
This should not happen in case of your web site cookies. Note that the cookies
written by one domain say rediff.com can’t be accessed by other domain say
yahoo.com unless and until the cookies are corrupted and someone trying to hack
the cookie data.
8 ) Checking the deletion of cookies from your web
application page: Some times cookie written by domain say rediff.com may be
deleted by same domain but by different page under that domain. This is the
general case if you are testing some ‘action tracking’ web portal. Action
tracking or purchase tracking pixel is placed on the action web page and when
any action or purchase occurs by user the cookie written on disk get deleted to
avoid multiple action logging from same cookie. Check if reaching to your
action or purchase page deletes the cookie properly and no more invalid actions
or purchase get logged from same user.
9) Cookie Testing on Multiple browsers: This is the
important case to check if your web application page is writing the cookies
properly on different browsers as intended and site works properly using these
cookies. You can test your web application on Major used browsers like Internet
explorer (Various versions), Mozilla Firefox, Netscape, Opera etc.
10) If your web application is using cookies to maintain the
logging state of any user then log in to your web application using some
username and password. In many cases you can see the logged in user ID
parameter directly in browser address bar. Change this parameter to different
value say if previous user ID is 100 then make it 101 and press enter. The
proper access message should be displayed to user and user should not be able
to see other users account.
These are some Major test cases to be considered while
testing website cookies. You can write multiple test cases from these test
cases by performing various combinations. If you have some different
application scenario, you can mention your test cases in comments below.
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