Scenarios in which to use automated testing - when to use automated versus manual testing

In a previous post (What is Automated Testing), I had talked about what is automated testing, and what are the benefits of automated testings. In this post, I will explain about some of the scenarios in which the use of automated testing is more likely (and beneficial). This is also part of the discussion about where to use manual testing versus where to use automated testing.
- There is a tremendous benefit to using automated software where the work is repetitive and follow a certain pre-defined set of cases. Consider the case where a team is working on a set of features for a new version of the product. The team needs to also ensure that earlier released features continue to work and are not impacted by any changes in code in other parts of the application. This can be done through the process of automating the test cases for these features, so that the testing happens automatically every time a new build is released.
- When a large number of test cases have to be carried out in a fixed time frame, then these can be done through automation. Automation will typically execute a large number of test cases in a much shorter time frame than manual testing.
- Allows load testing. When you need to simulate situations where there are a large number of users load testing the system, automation can help to a great deal in such cases. For applications that are seeking to evaluate their performance under stress conditions, automation is necessary.
- Testing with a large number of different inputs. Suppose there is a software that takes inputs from the user, and produces an output. In such cases, the testing for the input cases would need to consider a range of different inputs, including acceptable values and a range of unacceptable values. These are done far better through automation testing, since doing this manually involves a lot of effort.
- Automated testing can be tweaked to do a number of tests that would be difficult for people otherwise. For example, during the course of a normal product development cycle, thousands of files can be touched, and it is impossible to test all the changes on a regular basis, especially for stuff such as security errors (and there can be many types of checks that the development team would want to do)
And there can be more benefits, would love to hear more from people who use automated testing ..