When it comes to test automation, I use a very arbitrary method based on experience that 80% of all tests should be automated.

This has worked well in practice, but is based more on "voodo" than science.

Should I instead be performing a mini return on investment analysis for each test to work out which ones I are good automation candidates?

Should I just focus on the buggiest areas of the application?

What are some good method(s) to determine when a test should be automated or not?

Is there a simple criteria that can be applied, or is it truly a black art?

  • There's something to be said for voodoo that works :)
    – corsiKa
    May 26, 2011 at 15:39
  • Question, Bruce... are you talking general "automated testing" or the specific subset of "automated regression testing"? Depending upon what you're doing, there are additional things you'll want to consider for automated regression... (see sqa.stackexchange.com/q/656/453) for a conversation on the difference. May 27, 2011 at 14:01

12 Answers 12


I think its hard to determine what is a "Best Practice" in this field since many aspects of software/hardware under test tend to be customized to the environments they are developed for what works in one environment does not work in another. There are generics, such as highly repetitive tasks that have low return or have standard results which make good candidates for automation. Other aspects of the environment are pretty much subjective, and you know what areas would best be suited to automation either by their stability or the way they work where you know that X input may only result in Y output or set Z though which you can verify one of many results depending on some external factor.

Decided to automate is hard, but I believe we know our environments best and can decide what tasks are:

  • repetitive
  • simplistic
  • free up time for more complex tasks
  • are stable enough
  • provide a good measure of confidence in stability and quality
  • deterministic, will yield pass/fail without false results

Those are usually the criteria I go by.

  • I would add deterministic to your list, as differentiated from "stable enough". I tend to think of "stable" as a feature of the component being tested (rate of churn/change), while "deterministic" to be will it always pass when things are good and fail when there is a problem, without false positives.
    – Tom E
    May 26, 2011 at 20:56
  • Good point, I'll add that to the list.
    – MichaelF
    May 27, 2011 at 11:49

I always think through the ROI to make my decision. I don't do anything formal, I usually just ask myself a few questions. This is generally a quick mental exercise. Things to consider (in order of priority).

  1. What will the impact to the user be if this code fails?
  2. How many users will a failure in this area affect?
  3. How likely is it that this code will fail in the wild?
  4. How often is this code expected to change after release?
  5. How long will it take to automate?
  6. How long does it take to test manually?

Thought of this way, it's usually pretty easy to decide.

  • 1
    +1 : ROI is really the only measure, though some people will weight different "Return" differently and some will weight "Investment" differently. I'd add: How many times will the test be run, as that will impact the answers to your points 5 and 6. If the test is only run once, meh. If it's run many, many times you keep reaping the benefits.
    – Peter K.
    May 28, 2011 at 23:59
  • Of course, it can be hard to quantify ROI.
    – user246
    Jun 20, 2011 at 22:20
  • While ROI seems to be a good measure, I have to object to "3. How likely is it that this code will fail in the wild?" and "4. How often is this code expected to change after release?". Regarding 3.: If you think that you can estimate the likeability of an error, you have already failed. Errors often appear in the most unlikely places. And sometimes these errors are most critical. Regarding 4.: It is not necessarily the code itself that changes, but maybe code that it depends on, so this is not a good criteria, either. Having said that, I think that the ROI can not be determined beforehand. Jul 16, 2014 at 10:36

I'd recommend looking at tedious, highly repetetive tests that need to be repeated on a regular basis. For instance, if you're routinely spending several days on manual regression in a specific area of the application each time you release, it's probably a good candidate for automation.

I don't think there is a "best practice" for what should be automated, because the decision depends a lot on the application under test, the environment, legislative requirements, hardware dependencies, and potential impacts.

In my place of work, for instance, the goal is to automate as much of the transactional testing as we can - because we develop point of sale systems for a niche industry, and need to be able to handle a variety of tax scenarios for customers who face serious financial issues if the calculations are even slightly off (among other things). We focus on transactions over configuration because transactions happen more often in the live environment, and because transactions are far more important to our customers than the setup. If they need to use an awkward workaround to set up, that's not as bad as if they can't sell something.

Of course, the best internal ROI can be achieved by automating the one task everyone in your team utterly detests! (Tax regression.... at least in my world).


I am assuming that the test case can be automated. Also assuming that one already has their sanity test cases / happy path automated.

  • Repetitive / Important - Is this test case going to be tested all the time / most of the time? - This also gives an indication of the importance of the test case.
  • Stability - If the module of the application is not stable enough, the effort in automation is wasted to an extent.
  • Utility TCs - Certain test cases need to be executed frequently to create setup e.g. Testing of multiple modules might require that an order be created each time (TC to create an order).
  • Complexity - If a TC needs complex steps or calculations
  • 1
    • These are good considerations that go into the ROI you will get when automating something. I especially like that you covered Utility items.. this is a case where automation is a test tool to aid manual testing (or other automated testing), it might be getting the system into a known state, or populating with known data etc.. This is a great use for automation beyond the automating of test cases, and is something that should not be neglected when considering where to utilize automation resources. May 30, 2011 at 1:29

    Depends on what you are trying to achieve out of Automating a test:

    1. Is it need based automation? E.g. - you can not run the test/observe the test results accurately in a non-automated manner. It is a very controlled test environment.

      Here the question of "when" does not arise. You just have to take a call whether to automate a test or not.

    2. Is the time based automation? E.g. - regression tests. Generally these are the ideal candidates for automation and that usually takes place when the functionality has 'matured', when you have a safe level of confidence in the stability of future (including a risk analysis of visible changes).

      For such candidates, firstly, automation is easier to develop ,tests are more reliable(false failures are less probable) and you can concentrate on "new" functionalities to test.


    Buggiest first is not always a good choice, you might want to leave the buggiest areas to experienced exploratory testers. I usually start by sorting the tests by their expected complexity level. Then I further sort by groups of related tests, and for each group define what is the needed infrastructure. In many cases your ROI will be better by implementing a lot of simple tests rather than few complicated tests so I begin by doing a group of related simple tests and their related infrastructure. I will usually choose a group that has more in common with others.


    I am afraid of using word "best practice" but I suggest to automate tests from the very beginning, at least not to wait till application UI is available to you. I begin with Selenium test as soon as I have application mock available to me. Only part I would be missing on are application objects and I fill these place holders once I have app UI available to me.

    This approach works well when you are not hard coding app objects in test itself and externalizing application navigation using Page Object.

    Apropos of, what to automate: If you have large application and least resources available (which is very practical) for automation then first pick up your User Acceptance Tests and also the scenarios which have resulted in defects.

    But if you have umpteen resources (which I highly doubt) then sea is the limit...


    I would suggest that things that take the longest time to test manually would be best candidates for automation. This then frees up more time for you to perform exploratory testing (which is where you are most likely to find the horrible defects).


    What is the business time-frame and mind-set for ROI ?


    • Startup business. User growth is everything. Limited device and browser testing is ok.

    • Growth Company. User acquisition is everything. Important to test and support many devices.

    • Revenue based, cost cutting company. Reduction in cost of manual testing when replaced by automated testing is attractive.

    Other factors:

    • revenue / profit
    • cost of automation
    • devices supported
    • product complexity
    • cost of manual testing
    • number of cases to test
    • history of failure ('fragility')
    • development style, e.g. Agile, TDD, BDD, etc.
    • cost of automation slowing down short-term development
    • cost of failure, e.g. nuclear power plant vs code linting tool
    • importance, e.g. national health care system vs local chess club
    • ability to fix later, e.g. voyager space probe vs local computer script
    • bullet lists that get longer with each bullet point until the last is really long

    Given how many factors there are, ROI will end up being part, but not all, of the final calculation.


    Test case selection should be in such a way that automating it should add value to the project in terms of cost, time saving etc.

    Following are the points I keep in mind to select tests for automation:

    • Test case executed with different set of data

    • Test case executed with different browser

    • Test case executed with different environment

    • Test case executed with complex business logic

    • Test case executed with different set of users

    • Test case Involves large amount of data

    • Test case has any dependency

    • Test case need to execute number of times


    When to Automate

    • Functionality of Feature is Tested & Stable
    • In Case of Frequent Builds, Regression Testing of this feature would reduce test execution time
    • You have required skill / time available to automate & maintain. You have a Automation Framework in place (configurable, Rerunnable ,Data Driven, Continious Integration, Scheduling)

    When Not to Automate

    • Feature is not stable
    • Feature is changed in every build. A/B testing experiments are done on the feature
    • No time / resource available for automation
    • Project is in sustenace mode / End of Life. There is no tangible ROI from Automation

    Also, Please check article Automation Testing versus Manual Testing Guidelines


    I referred this article long back. Article provides good clarity on Automation guidelines


    Test Automation Make Sense

    • When there are many repetitive tests
    • When there are frequent regression testing iterations
    • When you need to simulate large number of users who are using the application resources
    • When AUT is having comparatively stable UI
    • When you have large set of BVT cases

    Want to select Automation Tool for Your Project? Automation testing success largely depends on the selection of right testing tools. It takes lot of time to evaluate relevant automation tools available in the market. But this is a must one time exercise that will Here are the criteria you need to consider before selecting any testing tool:

    1. Do you have necessary skilled resource to allocate for automation tasks?

    2. What is your budget?

    3. Does the tool satisfy your testing needs? Is it suitable for the project environment and technology you are using? Does it support all tools and objects used in the code? Sometime you may get stuck for small tests due to inabilities of the tool to identify the objects used in the application.

    • Like your answer to a different question, your comments are relevant, but you really need to indicate your relationship to Indiumsoft.
      – Kate Paulk
      Jan 12, 2015 at 12:10

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