The needs for test automation changes in a microservice architecture compared to a monolith or traditional SOA. Even more so if we combine microservices with continuous delivery. What and how we choose to test has a large impact on how successfull we will be with microservices. If we choose wisely we can take advantage of the architecture to get good test coverage and confidence relative to the effort. This talk gives guidance about effective levels to test at and how to use DDD techniques to guide the effort.

1. EFFECTIVE TESTING IN
MICROSERVICE SYSTEMS
CHRISTIAN HORSDAL
@CHR_HORSDAL
@HORSDAL@MASTODON.NU
C.HORSDAL@GMAIL.COM

2. ABOUT ME
Christian Horsdal Gammelgaard
Independent Consultant
www.horsdal-consult.dk
c.horsdal@gmail.com
@chr_horsdal
@horsdal@mastodon.nu

3. WHAT TO TEST?
Confidence to deploy to production
Maintenance effort
100+ services
Bringing it all up locally is not an option

4. THE 6 CHARACTERISTICS
OF MICROSERVICES
A microservice
1. Is responsible for a single capability.
2. Is individually deployable.
3. Consists of one or more processes.
4. Owns its own data store.
5. A small team can maintain a handful of
microservices.
6. Is replaceable.

5. EXAMPLE: LOYALTY PROGRAM

6. WHAT IS THE SCOPE OF A MICROSERVICE?
The primary driver for
scoping microservices is
business capabilities
A microservice is responsible
for a single business
capability

7. LOYALTY PROGRAM
CAPABILITIES
• Issue cards
• Cancel cards
• Award points
• Raffle
• Track eligibility for special offers
• Special events

8. Loyalty cards
microservice
Loyalty points
microservice
Raffle
microservice
Eligibility
microservice
Special Events
microservice
Loyalty Program Bounded
Context

9. Generic 3rd party
Core
Supporti
ng

10. LEVELS OF TESTS

11. THE TEST PYRAMID
Adapted from
Mike Cohn, Martin Fowler
More effort
Less effort

12. THE TEST PYRAMID
• System level test:
• Test the complete system
• Black box
• Most important use cases

13. THE TEST PYRAMID
• Service level test:
• Test one complete
microservice
• Other microservices are
stubbed
• Grey box
• All important scenarios
• Positive and negative
• Test the business capability
• Contract tests

14. THE TEST PYRAMID
• Unit test:
• Test a unit of behavior
• White box
• Detailed
• Try to avoid mocks

15. SERVICE LEVEL TESTS – BEHAVIOR

16. SERVICE LEVEL TESTS

17. SERVICE LEVEL TESTS
Loyalty Program microservice
Mocked Special Offers
microservice
Send canned event

18. SERVICE LEVEL TESTS
Loyalty Program microservice
Mocked Notifications
microservice
Send command
Send canned response

19. SERVICE LEVEL TESTS
Service level test
scenario
Mocked
notifications
microservice
Loyalty Program
microservice
Send canned event
through real queue
Real HTTP request
Integration test process

20. SERVICE LEVEL TESTS
Mocking other services:
The test process is a .NET app
MVC can run in any .NET app
RabbitMQ subscriptions can run in any .NET app
⇒ Just create endpoints with MVC
⇒ And just use the bus

21. MOCKING OTHER SERVICES
public class NotificationsMock : Controller
{
public static bool ReceivedNotification = false;
[HttpPost("/notify")]
public OkResult Notify()
{
ReceivedNotification = true;
return Ok();
}
}

22. HOSTING MOCKED SERVICES IN TEST PROCESS
public MocksHost(int port)
{
this.hostForMocks =
Host
.CreateDefaultBuilder()
.ConfigureWebHostDefaults(x => x
.Configure(app =>
app
.UseRouting()
.UseEndpoints(opt => opt.MapControllers()))
.UseUrls($"http://localhost:{port}"))
.Build();
new Thread(() => this.hostForMocks.Run()).Start();
}

23. public class RegisterUserAndGetNotification : IDisposable
{
...
public RegisterUserAndGetNotification()
{
this.serviceMock = new MocksHost(mocksPort);
this.loyaltyProgramHost = new HostBuilder()
.ConfigureWebHost(x => x
.UseStartup<Startup>()
.UseTestServer())
.Start();
this.sut = this.loyaltyProgramHost.GetTestClient();
}
[Fact]
public async Task Scenario()
{
await RegisterNewUser();
await PublishSpecialOffer();
AssertNotificationWasSent();
}

24. MICROSOFT.ASPNETCORE.TESTHOST
private async Task RegisterNewUser()
{
var actual = await this.sut.PostAsync(
"/users",
new StringContent(
JsonConvert.SerializeObject(new LoyaltyProgramUser()),
Encoding.UTF8,
"application/json"));
Assert.Equal(HttpStatusCode.Created, actual.StatusCode);
}
private async Task PublishSpecialOffer() {... }
private void AssertNotificationWasSent()
{
Assert.True(NotificationsMock.ReceivedNotification);
}

25. SERVICE LEVEL TESTS – CONTRACTS

26. https://martinfowler.com/bliki/ContractTe

27. SERVICE LEVEL TESTS
Loyalty Program microservice
Mocked Notifications
microservice
Send command
Send canned response

28. SERVICE LEVEL TESTS
Service level test
scenario
Mocked
notifications
microservice
Loyalty Program
microservice
Send canned event
through real queue
Real HTTP request
Integration test process

29. TEST THE CONTRACT
Contract test based on
Mocked Notifications
microservice
Send command
Send real response
Notications
microservice
Assert
real response= canned response

30. MAKE THE IMPLICIT EXPLICIT
Service level test
scenario
Mocked
notifications
microservice
Loyalty Program
microservice
Send canned event
through real queue
Real HTTP request
Integration test process

31. HELPFUL TOOLS
Pact
https://docs.pact.i
o/
mountebank
http://www.mbtest.
org/

32. UNIT TESTS – BUSINESS AS USUAL

33. PRIORITIZING WHAT TO TEST

34. OUTSIDE-
IN TDD
• Write high level test first
• Drive till it hurts
• Shift down
• Repeat
Write test
Write
production
code
Refactor

35. CORE DOMAIN CHART
https://github.com/ddd-crew/core-domain-charts
Loyalty program
Personal shopper AI
Notifications
Authentication

36. Generic 3rd party
Core
Supporti
ng

37. TL;DR: FOCUS ON SERVICE LEVEL TESTS
• Service level test:
• Test one complete
microservice
• Other microservices are
stubbed
• Grey box
• All important scenarios
• Positive and negative
• Test the business capability
• Contract tests

38. ABOUT ME
Christian Horsdal Gammelgaard
Independent Consultant
www.horsdal-consult.dk
c.horsdal@gmail.com
@chr_horsdal