Friday, 6 September 2013

Code coverage and Unit tests in VS2012

This post is about a question that people often asks when writing Unit tests and What troubles a developer is:

When should I stop writing Unit tests of something(Let say a simple Function)?

Lets talk about something known as Code coverage feature in visual studio(Premium/Ultimate editions). Most of the people don’t even know how it can help identifying unused code. Code coverage actually do the instrumenting of the assembly with special symbols putting over each statement and then analyse if that is being called when the code was getting executed. In visual studio this feature is added with Test manager. So you can run your unit tests via coverage tool and analyse the report how much production code is being covered by your unit tests.

Lets see how to run tests with coverage in simple steps:

1. In visual studio 2012 (Premium/Ultimate) you’ll find the option Test –> Analyze code coverage. Now there’s an option to run a single test coverage or all tests coverage.


Note: This option will be enabled only when your solution have UnitTests available. For unit tests written with Nunit you will need an Nuget package for Nunit Test Adapter. If you want then you can also download the Nunit VS Extension by searching into the VS Extension online.

2. Now select Run All Tests option and the magic will start. The coverage tool will be automatically launched and will run all Unit tests.

3. Once all the unit tests are done with running. You’ll see a coverage report in Code coverage Results window which will give you coverage in %.


In this report you’ll see in the Covered column the percentage of every function. And if this report says 100% then

Writing Unit tests at the moment.

Though as a standard testing strategy you can stop when coverage is >95%.