Clean Test Code

David Völkel, @davidvoelkel
Clean Test Code
Agile Testing Days 11.11.2014

2
@davidvoelkel
Dev & Consultant
Software Craftsman
Test-Driven Development
Software Design
@softwerkskammer

Dirty Test Code
technical debt
velocity decrease
costs
latency
agile

Clean Tests
4 attributes reliable readable redundancy-free focused Conclusion Q&A

xUnit- Patterns
BDD
Functional tests
setup
arrange
given
Input rows
execute
act
when
“Fixture“
verify
assert
then
Output rows
[teardown]
[annihilate]
Test Phases
Input
Output

Reliable
Mind complexity, so avoid
•boolean assertions
assertTrue(age >= 18);
assertThat(age, greaterThan(17))

Reliable
Mind complexity, so avoid
•boolean assertions
•conditionals & complex loops
boolean containsName = false;
for (String name: names) {
if (name.equals("David")) {
containsName = true;
}
}
assertTrue(containsName);
assertThat(names, hasItem("David"));

Readable
Read >> write
Executable specifications
Living documentation

Abstraction
avoid irrelevant details

Test Method Body
Gerard Meszaros:
„When it is not important for something to be seen in the test method, it is important that it not be seen in the test method! “

“In the order form the user should be able to finish the order process by pressing the cancel button”

@Test public void cancelProcess_inOrderForm() {
server.runningProcesses(0);
ProcessStatus process = server.startProcess(Process.ORDER);
processInstanceId = process.getInstanceId();
server.expectUserForm(processInstanceId, ORDER_FORM);
Form form = new Form();
form.setOrderDate("01.01.2015");
form.setStandardDelivery(false);
String taskId = server.taskIdFor(processInstanceId);
controller.submit(form,
Mockito.mock(BindingResult.class), null,
taskId, null, CANCEL);
}

ProcessStatus process = server.startProcess(Process.ORDER);
}
„Testscript“
“Incidental Details”

ProcessStatus process = server.stareProcess(Process.ORDER);
}
FORM
CANCEL
Signal-Noise-Ratio?
Single Level of Abstraction?

inForm(ORDER_FORM);
submitFormWithButton(CANCEL);
noProcessRunning();
}

Test class names
public class AnOrderProcess {
OrderProcess process;
@Before public void createOrderProcess() {
process = new OrderProcess();
}
object under test

}
@Test public void inOrderForm_cancel() {
process.setState(ORDER_FORM);
process.submit(CANCEL_BUTTON);
assertThat("process canceled", process.isCanceled(), equalTo(true));
}
Test method names
object under test

}
}
Test method names
object under test
setup

}
}
Test method names
setup
execute

}
}
Test method names
setup
execute
verify

Audience?
test maintainer
search test failure cause
business

Communicate
comprehensively
OuT + setup + execute + verify
Distribute: Class, method name, verify

Hierarchical tests
}
public class InOrderForm {
@Before public void inOrderForm() {
}
@Test public void whenCanceled_processIsStopped() {
assertThat("process stopped", process.isStopped(), equalTo(true));
}
@Test public void whenBought_orderIsConfirmed() {
process.submit(BUY_NOW_BUTTON);
assertThat("state", process.getState(), equalTo(ORDER_CONFIRMED));
}
}
…
extract common
setup

OuT
Hierarchical tests
setup
execute
verify

Helper methods
Object Mother
Test Data Builder
aCustomer("David");
CustomerTest.aCustomer("David");
CustomerMother.aCustomer("David");
CustomerMother.aCustomer("David", „Völkel");
CustomerMother.aCustomer(null, „Völkel", null, null, null, null, birthday);
aCustomer().withLastName("Völkel")
.withBirthDay(birthDay)
.build();
Common test data

void assertMoneyEquals(Money expected, Money actual) {
assertEquals("currency", expected.getCurrency(),actual.getCurrency());
assertEquals("amount", expected.getAmount(), actual.getAmount());
}
Matcher<Money> equalTo(Money money) {
return allOf(
property(money, Money::getCurrency, "currency"),
property(money, Money::getAmount, "amount"));
}
Custom asserts via helper methods
Composed Hamcrest Matchers
Common verify

"Single Concept per Test"
"One Execute per Test"
"One Assert per Test"
Focused

State vs. testability
Focused

„Listen to your tests!“
Hard-to-test Code

Clean Tests
1.reliable
2.readable
3.redundancy-free
4.focussed

Resources
Books
„Clean Code“, Robert C. Martin
„xUnit Test Patterns“, Gerard Meszaros
„Effective Unittesting“, Lasse Koskela
„Growing Object Oriented Software“, Steve Freeman, Nat Pryce
„Specification by Example”, Gojko Adzic
Videos
Episodes 20-22 http://cleancoders.com/,
Robert C. Martin

David Völkel
codecentric AG
Twitter: @davidvoelkel
david.voelkel@codecentric.de
www.codecentric.de
blog.codecentric.de
Q&A
35

Creative Commons ShareAlike 4.0
The images used are public domain and can be found on Wikipedia.
License
36

Clean Test Code

More Related Content

What's hot

Viewers also liked

Similar to Clean Test Code

More from David Völkel

Recently uploaded

Clean Test Code