Writing a good unit test

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Writing a good unit test

If you are one of those affected, spare few minutes and consider these reasons for NOT writing unit tests: Return on investment of unit tests is an order s of magnitude lower than that of end-to-end tests.

If you write a single end-to-end test the execution of the test will probably cover a substantial part of the codebase: If you write a single unit test, you cover just a small piece of the codebase: If you are painting a house, you want to start with a biggest brush at hand and spare the tiny brush for the end to deal with fine details.

If you begin your QA work with unit tests, you are essentially trying to paint entire house using the finest chinese calligraphy brush.

End-to-end tests test the critical path. Unit test do not. End-to-end tests typically simulate real-world usage scenarios. Thus, after running end-to-end test you have reasonable level of confidence that the product is going to work for the actual user. If all you have are unit tests, you are pretty sure that all the individual gears inside the project work as expected.

However, you have no idea whether the project as a whole works or not. Yes, unit tests are rigorous and make sure that the component will work even in corner cases.

However, user wants the product to work in common cases in the first place. On the other hand, if the product fails in exotic cases that happen rarely or never at all, the defect can be tolerated and possibly fixed later on. Unit tests ossify the internal architecture.

Imagine you have three components, A, B and C. You have written extensive unit test suite to test them. Later on you decide to refactor the architecture so that functionality of B will be split among A and C.

Test-driven development - Wikipedia

All the unit tests are suddenly rendered useless. Some test code may be reused but all in all the entire test suite has to be rewritten. This way the unit test suite makes the product resistent to internal change.

A programmer with limited time to allocate on tasks will consider the refactoring, then consider the cost of rewriting the test suite and place to whole endeavour into the "not worth it" mental slot.

I have seen a nice definition of "architecture" somewhere. It said that architecture is that what makes software able to change.

If we embrace this point of view, unit tests can be considered to be a strictly an anti-architecture device. Consider a protocol decoder. The protocol says "9th byte in the packet is called TLL". The implementation does this: You can create a fake packet that has value as 9th byte and then check that the decoder extracts TTL of What works though is interoperability testing: Take two implementations of the same protocol and check whether they speak each to another.

And once again, we end up with end-to-end tests instead of unit tests. Some stuff has no rigorous acceptance criteria.As an outspoken and opinionated guy, David Heinemeier Hansson (a.k.a.

DHH), creator of Rails, is no stranger to a little bit of rutadeltambor.com frequently sets off interesting debates on Twitter from his @dhh account.


The latest is, perhaps, the most involved yet and . Dec 15,  · This post will show you how to pass load test context parameters to a unit test.

writing a good unit test

This may be useful if you have some variables that you want to be able to change for each running of a load test. My simple example will show you how to create a load test plug-in which will. rutadeltambor.com (GSO) is a free, public website providing information and resources necessary to help meet the educational needs of students.

How to use this test: First, if you're unsure of what a Mary Sue is, please read this page. Answer all questions for which the answer is 'yes' or 'technically yes' unless the item mentioned is so commonplace in the universe you are writing for that it doesn't really make your character remarkable or.

Vigorous writing is concise.

writing a good unit test

A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. Pearson Prentice Hall and our other respected imprints provide educational materials, technologies, assessments and related services across the secondary curriculum.

Unit Test Basics in Visual Studio - Visual Studio | Microsoft Docs