It’s 2021, so practices like Test Driven Development (TDD) have long found their way into organizations. However, the practices and principles to keep those unit tests maintainable haven’t really changed. Still, Dennis regularly talks to developers that somehow ended up with an incomprehensible unmaintainable set of unit tests that they once believed in, but are now holding them back. So in this session Dennis likes to provide a refresh of those fundamental ideas and talk about why you should practice TDD, revealing intentions, naming conventions, state versus interaction based testing, and how to stay out of the debugger hell with proper mocking and assertion frameworks.

1. Dennis Doomen | @ddoomen | Aviva Solutions | The Continuous Improver

4. (An opinionated definition)

5. …is fast
(< 50ms)

6. …runs
in-memory

7. …can be run in
any order

9. …causes no
collateral
damage

10. …has no static
dependencies

11. …has no I/O-
bound
dependencies

12. …can be run in
parallel

14. UI Automation
HTTP/API Tests
Component /
integration Tests
Unit Tests

15. (in my definition)

16. Design class
responsibilities
Write first unit
test
Generate stubs
Fail for the right
reason
Implement
real deal
Ensure test
succeeds
Identify
alternative
scenarios
Repeat twice
Refactor

18. Test against
observable
behavior

19. Test at the
right scope

20. If it’s not important
for the test, it’s very
important to hide it

21. Crystal-clear
cause and
effect

22. Reads like
a book

23. Copy two
times before
refactoring

24. Use fakes
when you
need to

26. eventMonitor.OccurredEvents.Should().BeEquivalentTo(new[]
{
new
{
EventName = "PropertyChanged",
TimestampUtc = utcNow - 1.Hours(),
Parameters = new object[] { “third”, “first”, 123 }
},
new
{
EventName = "NonConventionalEvent",
TimestampUtc = utcNow,
Parameters = new object[] { "first", 123, "third" }
}
}, o => o.WithStrictOrdering());

28. Command Handlers
Commands
Domain Model
Event Store
Events
App
Read Data
RavenDB
Projectors
Events
HTTP API
Projections
Events

30. Test Fixture
In-Memory
Event Store
Read
Data
RavenDB
Projectors
Events
HTTP API
Projections
Unit Test
HTTP request
Test Data

32. • Choose the appropriate type of
testing
• Care about the boundaries
• Write intention-revealing test
• Avoid DRY.

33. Dennis Doomen | @ddoomen | Aviva Solutions | The Continuous Improver
…then ping me at @ddoomen
…or email me at dennis.doomen@avivasolutions.nl