Struggling to Create Maintainable Unit Tests?

Protocol => Mocks

Data => Builders

Roadmap

• Define Maintainable Unit Test

• Create a Shared Vocabulary

• Examples

• When to Use Mocks

DefineMaintainable

Unit Test

10% of Unit Tests Break

If you really have a lot of unit tests, the amount of investment you'll have to makein maintaining those unit tests, keeping them up-to-date and keeping them passing, starts to become disproportional to the amount of benefit that you get out of them.

— Joel Spolsky

Maintainable Unit Tests

The benefits of unit tests outweigh the costs as a codebase evolves.

SharedVocabulary

Mocks

Builders

xUnit Test Patterns

Mocks

Builders

Mock Object

A mock object is a simulated object that mimics the behaviour of a real object in controlled ways.

Test Data Builder

• Builder Pattern

• build() method

• Default values

• Chainable configuration methods

Shared Vocabulary

• 4–Phase Test

• System Under Test

• Depended–On Component

• Mock Objects

• Test Data Builders

Examples

Domain Model

public void should_recognize_pediatric_patient(){ // setup Patient sut = aPatient().age(17).build();

// exercise and verify assertTrue(sut.isPediatric()); assertTrue(!sut.isAdult());}

public void should_recognize_pediatric_patient(){ // setup Patient sut = aPatient().age(17).build();

// exercise and verify assertTrue(sut.isPediatric()); assertTrue(!sut.isAdult());}

public void should_recognize_pediatric_patient(){ // setup Patient sut = aPatient().age(17).build();

// exercise and verify assertTrue(sut.isPediatric()); assertTrue(!sut.isAdult());}

aPatient().dob(april(1, 1992)).build();

Add Patient to Care Team

• Patient must be registered at the same Facility as the Care Team.

• Patient must meet the Care Team Membership Criteria (appropriate Age Category and Diagnosis).

public class CareTeamMembershipService implements ICareTeamMembershipService{ private CareTeamMembershipDao careTeamMembershipDao;

public void addMember(Patient patient, CareTeam careTeam) { if (!patient.isRegisteredAt(careTeam.getFacility())) { throw new CareTeamAdminException(); } if (!patient.meets(careTeam.getMembershipCriteria())) { throw new CareTeamAdminException(); } careTeamMembershipDao.create( patient.getId(), careTeam.getId()); }

}

private final CareTeamMembershipDao careTeamMembershipDao = context.mock(CareTeamMembershipDao.class); private final ICareTeamMembershipService sut = createCareTeamMembershipService();

public void should_permit_add_for_appropriate_care_team(){ // setup final Facility jacobi = aFacility().build(); final Patient patient = aPatient().at(jacobi).age(18) .with(Diagnosis.DIABETES).build(); final CareTeam careTeam = anAdultCareTeam().at(jacobi) .with(Diagnosis.DIABETES).build(); // verify context.checking(new Expectations() {{ one(careTeamMembershipDao).create( patient.getId(), careTeam.getId()); }}); // exercise sut.addMember(patient, careTeam);}

private final CareTeamMembershipDao careTeamMembershipDao = context.mock(CareTeamMembershipDao.class); private final ICareTeamMembershipService sut = createCareTeamMembershipService();

// verify@Test(expected=CareTeamAdminException.class)public void should_disallow_add_adult_to_pediatric_care_team(){ // setup final Facility jacobi = aFacility().build(); final Patient patient = aPatient().at(jacobi).age(18) .with(Diagnosis.DIABETES).build(); final CareTeam careTeam = aPediatricCareTeam().at(jacobi) .with(Diagnosis.DIABETES).build(); // exercise sut.addMember(patient, careTeam);}

Examples

• Test vs Production API

• Builders as shared test asset

• Mocks and Builders as Firewalls

When to Use Mocks

Mocks

Builders

Protocol

Data

Protocol => Mocks

Data => Builders

Now What?

• Read xUnit Test Patterns

• Read Nat Pryce’s Builder posts

• Distinguish Protocol vs Data

• Try using Mocks with Builders

Contact

Jason Cheong-Kee-Youj.chunky@gmail.com

Alistair McKinnella.mckinnell@computer.org

Resources

xUnit Test Patternshttp://xunitpatterns.com/

jMockhttp://www.jmock.org/

Test Data Buildershttp://nat.truemesh.com/archives/000714.html

Credits

Obstacle Racehttp://www.flickr.com/photos/foxypar4/1004464889/

Einstein Blackboard Writing Generatorhttp://generator.kitt.net/2006/12/einstein-blackboard-writing-generator.html

Holy Grailhttp://www.flickr.com/photos/spiritual_marketplace/2207966935/