On Slow Vs Fast, Co$tly Vs Cheap and stating the not so obvious
Automation testing is a must for agile teams that want to continuously deliver business value. Does test automation give value to agile teams? Automation testing gives value if it satisfies (at least) two important principles:
1) Provide fast feedback to developers (SPEED)
2) Be less expensive than manual regression testing over the application lifetime(CO$T)
SPEED is extremely important. Time is money. People don’t like waiting for something to happen while losing money, developers are no exception. Knowing that we will soon know if our code change worked or not, helps us re-factor that old piece of code that was unmanageable. If you will only know tomorrow that you have broken something, it might be very difficult to fix it because maybe 10 other people have pushed their changes after you and who knows who broke what? Imagine if it took you 1 day to compile your code, would you make that small optimization change? Be honest…
Fast tests give teams great benefit because they tell us straight away “well done!” you’re on the right path, or “hang on you made a mistake, fix it before it’s too late!”.
There are no two ways about it, slow tests are BAD. Developers hate running them because it is a pain, you either wait for them to complete and tell you how you did or you ignore them and go ahead with other changes. Both approaches are bad, while you wait for feedback you are losing money by not being able to code (time=money), if you make other changes you risk burying the “thing” you just broke under more broken code and guess what? You lose money!
CO$T is quite a big issue, isn’t it?
How do you like tests that are brittle and break as soon as something changes in the application user interface? VERY CO$TLY.
How about tests that take ages to run because are highly coupled and necessitate of the full End to End (E2E from now on) test environment to complete? SLOW & CO$TLY!
Slow because they rely on so many systems, as a consequence they keep on breaking but 80% of the times it’s a false positive because some System_XYZ that the test is using somewhere to provide some data was down or Database_ABC was accessed at the same time by another user that messed up the test data. Damn! Rerun the suite again, TOMORROW you will know if it passes, maybe, hopefully, unless something else is broken :-( SLOW, CO$TLY and worse than everything they become a hindrance to developers because they not only give no value but are counterproductive by wasting their time.
An automation strategy based on E2E tests run through the User Interface that follow the full application workflow has FAILURE written all over. Why? Because E2E UI driven automated tests are SLOW and CO$TLY. Developers hate them and when they catch the odd bug they might not even investigate and follow-up correctly because “…ah sure, it must have been something in the environment, like in the last 35 failures, damn test harness!”. They slowly become noise in the background and after a while nobody cares about them, they are abandoned and the automation effort deemed a failure.
But, hang on, we can avoid this.
Don’t write slow, highly coupled, UI driven, brittle, costly E2E automated tests, do yourself a favour, just don’t.
Yes but we need them, how do we show we verify the acceptance criteria?
Each individual system in a complex architecture can be built to adhere to acceptance criteria, individually. Let’s focus on each system and target our efforts there first. Let’s also automate integration points but let’s not forget about what we are testing when doing integration: we are testing the interfaces only, not the functionality of the other system we integrate to!
On Slow Vs Fast, Co$tly Vs Cheap and stating the not so obvious
Let me introduce you to Augusto’s 4 golden rules of Fast and Cheap automation testing. (yeah, that’d be me)
First – identify the application under test and focus: write a lot of tests that run against an individual system, they are much faster than coupled tests, they are also much cheaper because they won’t bother you with false positives. Remember, each system on its own can satisfy business acceptance criteria, it might take some time to formulate the acceptance tests describing business value but it is indeed possible. The business logic to be tested resides in the individual systems; test it where it is, not through another system.
Second – go under the hood:, unless you are testing specifically the user interface, write tests that are run against a system by using a service layer rather than the user interface itself. They are much faster and extremely more maintainable (not affected by UI changes). Go under the hood! Focus on the logic to be tested not the steps that are required to get to a certain state. Use mocks and stubs, invest in building such support tools tailored to your needs, they pay off oh yes they do.
Third – when integrating, focus on interfaces, write integration tests between pairs of systems; focus on testing the interfaces between the systems only, do not duplicate the testing you have already done on the individual systems. There is nothing worse than trying to test the business logic in SystemB by using SystemA, don’t do it! Test SystemB business logic in SystemB with fast tests as part of golden rule #1. Integrate SystemA and SystemB to verify that the communication between the 2 systems is not broken, test only that the communication works, do not test the functionality of either of the systems at this stage (you have already done it in rule#1).
Fourth – use your brain and do not duplicate slow process: if you can’t help it and you want to write E2E tests, limit drastically their breadth to cover the happiest paths you can think of, make sure you run them in a dedicated environment to avoid test data corruption and involuntary resource contention. Automating E2E testing in complex systems is a bad idea; use exploratory testing on new features instead.
Mike Cohen a few years back came up with a test automation pyramid that describes how the automation effort should be distributed. Unit tests represent the majority of tests, immediately after there are tests run through a Service layer and at the top we have only a few E2E tests run through the User Interface. I love Mike Cohen’s pyramid, thanks Mike!
To recap, I have illustrated my rambling in a “Dummy Test Automation Strategy For A Simple Multi System Architecture”. I am interested in your feedback, good or bad, please go for it, tell me what you think!