Isolated Unit Tests and Fine Grained Failures

Posted by Winston Ewert on Programmers See other posts from Programmers or by Winston Ewert
Published on 2014-08-23T17:21:15Z Indexed on 2014/08/23 22:33 UTC
Read the original article Hit count: 323

Filed under:

unit-testing

|

TDD

One of the reasons often given to write unit tests which mock out all dependencies and are thus completely isolated is to ensure that when a bug exists, only the unit tests for that bug will fail. (Obviously, an integration tests may fail as well). That way you can readily determine where the bug is.

But I don't understand why this is a useful property. If my code were undergoing spontaneous failures, I could see why its useful to readily identify the failure point. But if I have a failing test its either because I just wrote the test or because I just modified the code under test. In either case, I already know which unit contains a bug.

What is the useful in ensuring that a test only fails due to bugs in the unit under test? I don't see how it gives me any more precision in identifying the bug than I already had.

© Programmers or respective owner

Related posts about unit-testing

Unit testing best practices for a unit testing newbie

as seen on Programmers - Search for 'Programmers'
In recent years, I have only written small components for people in larger projects or small tools. I have never written a unit test and it always seems like learning how to write them and actually making one takes a lot longer than simply firing up the program and testing for real. I am just about… >>> More
About unit testing a function in the zend framework and unit testing in general

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello people, I am diving into the world of unit testing. And i am sort of lost. I learned today that unit testing is testing if a function works. I wanted to test the following function: public function getEventById($id) { return $this->getResource('Event')->getEventById($id); } So… >>> More
Unit testing a database connection and general questions on database-dependent code and unit testing

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, If I have a method which establishes a database connection, how could this method be tested? Returning a bool in the event of a successful connection is one way, but is that the best way? From a testability method, is it best to have the connection method as one method and the method to get… >>> More
What is the objective of unit testing?

as seen on Programmers - Search for 'Programmers'
I've been working with C# for the last 2 years, and I've never done any unit testing. I just need to know what the objective of unit testing is. What kind of results do we expect from unit testing? Is code quality checked by unit testing? In my view, unit testing is the job of testers; if that is… >>> More
Unit testing newbie team needs to unit test

as seen on Programmers - Search for 'Programmers'
I'm working with a new team that has historically not done ANY unit testing. My goal is for the team to eventually employ TDD (Test Driven Development) as their natural process. But since TDD is such a radical mind shift for a non-unit testing team I thought I would just start off with writing unit… >>> More

Related posts about TDD

TDD - How to start really thinking TDD?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have been reading about Agile, XP methodologies and TDDs. I have been in projects which states it needs to do TDD, but most of the tests are somehow integration tests or during the course of project TDD is forgotten in effort to finish codes faster. So, as far as my case goes, I have written unit… >>> More
Are "TDD Tests" different to Unit Tests?

as seen on Programmers - Search for 'Programmers'
I read this article about TDD and unit testing: http://stephenwalther.com/blog/archive/2009/04/11/tdd-tests-are-not-unit-tests.aspx I think it was an excellent article. The author makes a distinction between what he calls "TDD Tests" and unit testing. They appear to be different tests to him. Previous… >>> More
Doing TDD Silverlight 4 RC using Visual Studio 2010 RC

as seen on Stack Overflow - Search for 'Stack Overflow'
First I am glad to see better TDD support in VS2010. Support for generating code stubs from my tests is ok - not as good as more mature TDD plug-ins but a good start. I am looking for some best Silverlight 4.0 TDD practices. First Question: Anyone have links, recommendations? I know the new Silverlight… >>> More
Applying Test Driven Development to a tightly coupled architecture

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi all, I've recently been studying TDD, attended a conference and have dabbled in few tests and already I'm 100% sold, I absolutely love it TDD. As a result I've raised this with my seniors and they are prepared to give it a chance, so they have tasked me with coming up with a way to implement… >>> More
Integrating JavaScript Unit Tests with Visual Studio

as seen on Stephen Walter - Search for 'Stephen Walter'
Modern ASP.NET web applications take full advantage of client-side JavaScript to provide better interactivity and responsiveness. If you are building an ASP.NET application in the right way, you quickly end up with lots and lots of JavaScript code. When writing server code, you should be writing… >>> More