I’ve been doing that thing called DevOps for about 17 years – you know – before it had a name…
In fact it was when I first joined Jade Software that I realised that Ops and DEV had a common interest in making systems go. In 2002 I started working with our toolset team designing our in-house written toolsets to deploy JADE databases/systems automatically and reliably. Little did I know I would be repeating that methodology around .NET written systems in 2010 and then repeating it again with deploying SQL Server code in 2014…
The major breakthrough for the JADE applications and database was unit testing.
When we started developing in .NET (over a JADE database at the time) it made sense to do unit tests – in fact I don’t know of many good .NET developers who don’t do unit testing.
It was when I started speaking to audiences that I realised that not many people do unit tests for their databases. Why??
Well it appears I was talking to the wrong crowd…. sort of.
Code first developers who design databases using Entity Framework are used to writing unit tests so most times they are testing code that will change the underlying database.
So that led me to ask the question: “Are DBAs doing Unit tests?”
They are not.
Firstly – what is a unit test?
The primary goal of unit testing is to take the smallest piece of testable software in the application, isolate it from the remainder of the code, and determine whether it behaves exactly as you expect.
This testing is done as part of the development process, and a unit test will check that the code being tested meets a specification, while a library of unit tests together will check the functions expected of the application. By automating the process , which allows the library of unit tests to be run frequently, and repeatedly, it allows us to find bugs earlier, and in smaller units of code, which are far more easier to debug.
Unit tests should be self contained enough that you are isolated in what you are testing so that you know whether have a correctly performing test. Too often we think of databases as massive stores of data and generally we only test for performance. However – with unit tests we are looking at far smaller sets of data, we want tests that are fast and we are testing the functionality/quality of the code rather than the execution speed.
The upshot is that once we embrace unit testing we can then start to utilise regression testing which can allow us to refactor our database code just as easily (if not more confidently) as developers do for application code.
So if hiring a .NET developer who doesn’t do unit tests is unthinkable – why would we accept this as the norm for the people who are writing the stored procedures etc that touch/influence and ultimately own our most precious resource – our data…?
Because it is too hard?
I find tuning indexes and queries hard – writing a unit test to prove that my code won’t kill PROD seems way easier. Also if I find a bug in my code when I’m writing the code at 3pm – it’s way easier to fix it then than at 3am when an online banking system has crashed/burned or is now corrupt…. I’m sorry but saying unit testing is too hard is a cop out.
Because it is too slow?
Refer the example above – way easier to write a little bit of a unit test and prove that my change is going to work when it will only trash my DEV instance. Fixing it then is far quicker than when 1,000s of users are affect – because there are less people calling my phone/emailing me when I fix it in my DEV instance..
Because it is too new?
Not at all – SQL Server Data Tools (SSDT) has provided database developers the ability to do unit testing since 2012. https://blogs.msdn.microsoft.com/ssdt/2012/12/07/getting-started-with-sql-server-database-unit-testing-in-ssdt/
In fact there is an old article at SQLServer Central that is from 2009!! http://www.sqlservercentral.com/articles/Editorial/68586/
Because it involves learning a new language?
You don’t have to – tSQLt and SQLTest by Redgate both allow unit tests to be written in TSQL – which most DBAs thrive on. Even SSDT allow you to write unit tests in TSQL.
I have used SSDT a far bit so if you are a database developer then I highly recommend you read “Creating and Running a SQL Server Unit Test” https://msdn.microsoft.com/en-us/library/jj851212(v=vs.103).aspx
If you are a DBA then I highly recommend you look at tSQLt.org – the official website has lots of useful information. There is a slight learning curve – but after 15 minutes reading and trying it out – it is very simple to use. It allows you to isolate your testing to a particular schema and makes use of fake tables – equivalent of mocking –which allows us to take copy of the table as it is and test against it.
There is a great pluralsight course here: http://pluralsight.com/training/Courses/TableOfContents/unit-testing-t-sql-tsqlt
David Green is the author of the above Pluralsight course and has written a fair bit about tSQLt – http://d-a-green.blogspot.co.uk/search/label/tSQLt
Greg Lucas has also written a lot about tSQLt http://datacentricity.net/tag/tsqlt/
His article on http://datacentricity.net/2011/12/advanced-database-unit-testing-with-tsqlt-testing-cross-database-tables is particularly helpful.
Of course there are some other great utilities and I mentioned one earlier:
SQLTest by Redgate – which is an absolutely awesome tool for DBAs – mainly as it plugs straight into SQL Server Management Studio (SSMS).
It uses the tSQLt framework and incorporates SQLCop SQL Test which will help you enforce best practices for database development and run static analysis tests.
Best part is if you are on a DevOps for Database journey then you can fold those tests into your Continuous Integration processes to really bring up the quality of your database code. You need to start looking at unit tests – today.