My first ever talk to the London branch of the ACCU about unit testing SQL code with an xUnit style unit testing framework.

1. xUnit Style Database Unit Testing
ACCU London – 20th
January 2011
Chris Oldwood
gort@cix.co.uk

2. Presentation Outline
• Database Development Process
• The xUnit Testing Model
• Test First Development
• Continuous Integration/Toolchain
• Pub

3. Legacy Database Development
• Shared development environment
• Only integration/system/stress tests
• No automated testing
• Only real data not test data
• Referential Integrity – all or nothing
• No automated build & deployment

4. Ideal Development Process
• Isolation
• Scaffolding
• Automation

5. Example Testable Behaviours
• Default constraint
• Trigger to cascade a delete
• Refactoring to a surrogate key

6. NUnit Test Model
[TestFixture]
public class ThingTests
{
[Test]
public void Thing_DoesStuff_WhenAskedTo()
{
var input = ...;
var expected = ...;
var result = ...;
Assert.That(result, Is.EqualTo(expected));
}
}

7. NUnit Test Runner
• Tests packaged into assemblies
• Uses reflection to locate tests
• In-memory to minimise residual effects
• Output to UI/console

8. SQL Test Model
create procedure test.Thing_DoesStuff_WhenAskedTo
as
declare @input varchar(100)
set @input = ...
declare @expected varchar(100)
set @expected = ...
declare @result varchar(100)
select @result = ...
exec test.AssertEqualString @expected, @result
go

9. SQL Test Runner
• Tests packaged into scripts (batches)
• Uses system tables to locate tests
• Uses transactions to minimise residual
effects
• Output to UI/console

10. SQL Asserts
• Value comparisons (string, datetime, …)
• Table/result set row count
• Table/result set contents
• Error handling (constraint violations)

11. Setup & Teardown
• Per-Fixture (static data)
• Per-Test (specific data)
• Use helper procedures

12. Default Constraint Test
create procedure test.AddingTask_SetsSubmitTime
as
declare @taskid int
declare @submitTime datetime
set @taskid = 1
insert into Task values(@taskid, ...)
select @submitTime = t.SubmitTime
from Task t
where t.TaskId = @taskid
exec test.AssertDateTimeNotNull @submitTime
go

13. Trigger Test
create procedure DeletingUser_DeletesUserSettings
as
...
set @userid = 1
insert into AppUser values(@userid, ...)
insert into AppUserSettings values(@userid, ...)
delete from AppUser where UserId = @userid
select @rows = count(*)
from AppUserSettings
where UserId = @userid
exec test.AssertRowCountEqual @rows, 0
go

14. Unique Key Test
create procedure AddingDuplicateCustomer_RaisesError
as
...
insert into Customer values(‘duplicate’, ...)
begin try
insert into Customer values(‘duplicate’, ...)
end try
begin catch
set @threw = 1
end catch
exec test.ErrorRaised @threw
go

15. Automation
• Enables easy regression testing
• Enables Continuous Integration
• Performance can be variable

16. Test First Development
• Start with a requirement
• Write a failing test
• Write production code
• Test via the public interface

17. The Public Interface
• Stored procedures
• Views
• Tables?

18. Implementation Details
• Primary keys
• Foreign keys
• Indexes
• Triggers
• Check constraints
• Default constraints

19. Deployment Testing
Build version N+1
then run unit tests
Build version N
then patch to N+1
then run unit tests
==

20. Buy or Build?
• Batch file, SQL scripts & SQLCMD
• TSQLUnit & PL/Unit
• Visual Studio
• SQL Server/Oracle Express

21. “The Oldwood Thing”
http://chrisoldwood.blogspot.com
Chris Oldwood
gort@cix.co.uk