How to start with testing a Rails application?
I wouldn't say there is any one best set of testing tools out there; and the community definitely has not decided on any being standard in any way.
I highly recommend The RSpec Book from the Pragmatic Programmers-- about half of the book is on testing with Rails with Cucumber, RSpec, and browser simulators like Selenium. It's a comprehensive overview of the different situations you will find yourself in with Rails and what tools you might want to use in each situation.
Selenium is a framework to automate testing of user interface. Selenium script launches a browser window, goes to a web-page and manipulates page elements.
RSpec and Cucumber are tools for what is called "behavior driven development (BDD)". BDD is a development process where you have description of a separate feature, and some script (can be a Selenium script) that checks this feature. RSpec and Cucumber basically connect these two, so that when you run a test script, you see the list of features written in plain language and their testing status.
Selenium scripts can be written in a number of languages, while Cucumber scripts use Ruby. Documentation is OK for all of them, some knowledge of programming language is required though.
Starting links:
There are many tools for testing rails and other webapps from many different aspects. But if you are new to testing I highly recommend you start with learning Rails own testing framework before start using other tools.
Learning, and later mastering, one testing framework makes it easier in the future to understand pros/cons with other framework and make them work in unison.
You could start with testing the following things:
- Unit Testing your Models
- Functional Tests for Your Controllers
- Learning about Fixtures and how to load test data
I have seen many failed testing efforts, but I never saw them fail because they choose the wrong tool/framework. They fail because they don't know how to master the tools they use, and learn enough about the basics about testing.
Read more about Rails testing here.
http://guides.rubyonrails.org/testing.html
Manual Exploratory 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.
Read more about mixing Automated and Manual Testing in another of my answers here:
What test methods do you use for developing websites?