I'm aware of automation tools like- Selenium, Appium, Selendroid.
Is there any other tool available in the market which is used for automation testing outside of the selenium group?
By using these, it makes it far easier to:
But for the real answer, QA's knowledge and senses is the most advanced tool we have. The ability to intuitively detect an issue. The 'this just doesn't feel right to me' instinct that we develop that causes us to push deeper.
The most recent developments that I have observed are:
Running tests in the cloud. Companies like Sauce Labs and Browserstack are leaders here. There are many advantages to this, from the number of devices being tested to the number of parallels servers that can be used.
Increasing use of mocking and stubbing of components such as database and other services / micro-services, as noted by Paul Muir (+1) so that tests can run in milliseconds instead of seconds and minutes. A well-stubbed test suite of hundreds of (non-ui) tests should run in 5-10 mins and not just grow to unwieldy over time. This takes work.
Agile. As Agile is now a leading approach, automation specialist needs to develop automation within the agile process. This is a huge topic on its own.
Tools like jmeter for performance testing
Ruby and rspec provide the framework that capybara runs within and they are powerful frameworks in their own right and can be used flexibly in various situations.