When developing a website, I often need to test scenarios like this:
When user A logs in, she should see X button while user B can not
And doing this kind of testing requires me to do a lot of log in and log out with different test accounts, which is by no means convenient.
I wonder if there are any tool that can help me do this?
My suggestion would be to use two (or more, if needed) different browsers. They have their own sessions, therefore you can be logged in with both users at the same time.
As example, you can use Internet Explorer for one, and Mozilla Firefox for other user.
Pretty simple!
Apache JMeter is very good at this type of thing: http://jakarta.apache.org/jmeter/