Adopting TDD - by Don McGreal

© Improving Enterprises, Inc.
Applying Unit Tests &
Test-Driven Development
Don.McGreal@ImprovingEnterprises.com
@donmcgreal
linkedin.com/in/donmcgreal

The Plan...
Unit Testing
Test Driven Development
Behavior Driven Development
Getting the most from your tests
Q&A

“I don’t want to touch that! It’ll
take forever, and I don’t know
what else will break if I do.
I’ll just rewrite it.”
Familiar?

Unit Testing
Test the code quality
“Alarm System”
Regression testing
Reduce number of defects
Fix defects quicker
Confidence in the code
“Virtuous Cycle”
More Test
More Change
More Quality
More Confidence
CODE

Unit Testing
What is a Unit?
What is a Test?
Smallest testable part of an application
Validation that the code is working properly

Unit Testing - Traditional
public class MyClassTest {
[Test]
public void TestMethod1() {
MyClass instance = new MyClass();

instance.Method1();

Assert.AreEqual("expected", instance.Value);
}

[Test]
public void TestMethod2() {
MyClass instance = new MyClass();

Result result = instance.Method2();

Assert.IsNotNull(result);
Assert.AreEqual("expected", result.Value);
}
}
Exercise
Verify
Setup AreEqual(expected, actual);
AreNotEqual(expected, actual);
Greater(expected, actual);
Less(expected, actual);
IsFalse(condition);
IsTrue(condition);
IsNull(object);
IsNotNull(object);
IsEmpty(object);
AreSame(expected, actual);
AreNotSame(expected, actual);
Pass();
Fail();
Teardown

Unit Testing Example
Let’s try it...

Test Driven Development
Start
Here

Think
Test
Code
Design
2-10 Minutes
TDD Mantra

Refactor
Green
Red
Think
Test
Code
Design
2-10 Minutes
TDD Mantra

Step 0: Think
(take as long as you need*)
*Jim Shore

Step 1: Write a test.

Step 2: Make the test pass.
(Just barely)

Step 3: Refactor.

TDD lets you know when...
Y a
A i n ’ t
G o n n a
N e e d
I t !

“Only write code to fix a failing test”
So...

Case Study
Empirical studies compared 4 projects, at Microsoft and IBM, that
used TDD with similar projects that did not use TDD.
The findings were similar to other case studies:
Defect
density
decreased
40%–90%
Development time
increased by 15–35%
(though teams agreed
that this was offset by
reduced maintenance
http://www.infoq.com/news/2009/03/TDD-Improves-Quality

TDD Example
Let’s try it...

Unit Testing - BDD Style
public class WhenSystemIsInParticularState {
private MyClass instance;
[SetUp]
public void Init() {
instance = new MyClass();
}
[Test]
public void ShouldDoThisAndThat() {
instance.Method1();

Assert.AreEqual("expected", instance.Value);
}

[Test]
public void ShouldDoThatAndThis() {
Result result = instance.Method2();

Assert.IsNotNull(result);
Assert.AreEqual("expected", result.Value);
}
}
Setup
Exercise
Verify
assertEquals(expected, actual);
assertFalse(condition);
assertTrue(condition);
assertNull(object);
assertNotNull(object);
assertSame(expected, actual);
assertNotSame(unexpected, actual);
fail();
Teardown

Behavior Driven Development
Forget about Tests; Think about Specifications
it’s easy to come up with reasons not to test, but writing
specs can become an integral part of development
Forget about Units; Think about Behaviors
worry more about how a developer will interact with the
code, and not what methods a class has

BDD
BDD Frameworks for Java & .Net
• JBehave
• easyb (Groovy)
• NSpec
• nbehave
• others...

BDD Example
Let’s try it...

The Problem
 External dependencies affect
 Performance
 Portability
 Stability
... of your tests.
Application
Remote
Application
Data
This is an opportunity and a driving force to design more
modular, more testable and more re-usable code.

Integration Tests
 Testing external connections to
other systems and databases
are acceptable, but not as part
of the general test suite.
 These are called
Integration Tests
Application
Remote
Application
Data

The Solution
ClientApp RemoteBank
debit(amt):boolean
credit(amt):boolean
SoaBankJmsBank FakeBank
 Dependency Injection
bank
debit(amt):boolean
credit(amt):boolean
debit(amt):boolean
credit(amt):boolean
debit(amt):boolean
credit(amt):boolean

XUnit Patterns
 Test Doubles:
• dummies
• stubs
• fakes
• mocks

Dummy Object
 Null, "Ignored String", new Object()
public class ItemBehavior {
@Test
public void shouldCheckIfInventoryIsLow() {
Item item = new Item("name", 0.0, 10);
item.setQuantity(20);
assertFalse(item.isLowInventory());
item.setQuantity(2);
assertTrue(item.isLowInventory());
}
@Test
public void shouldStoreItemInformation() {
Item item = new Item("iPhone", 400.00, 10);
assertEquals("iPhone", item.getName());
assertEquals(400.00, item.getPrice());
assertEquals(10, item.getQuantity());
}
}

Test Stub
 Replace a real object with a test-specific object that
feeds the desired inputs into the system under test.
http://xunitpatterns.com/Test%20Stub.html
ClientApp app = new ClientApp();
RemoteBank bank = new FakeBank();
app.setBank(bank);
boolean success = app.debit(1000);

Fake Object
 Replace a component that the SUT depends on with a
much lighter-weight implementation.
http://xunitpatterns.com/Fake%20Object.html
RemoteLogger log = new FakeLogger();
app.setLogging(log);

Mock Object
http://xunitpatterns.com/Mock%20Object.html
 Replace an object the SUT depends on with a test-
specific object that verifies it is being used correctly
by the SUT.

Mock Object
http://xunitpatterns.com/Mock%20Object.html
public class MockLogger implements RemoteLogger{
public void logMessage(Date actualDate, String actualUser,
String actualActionCode, Object actualDetail) {
actualNumberCalls++;
Assert.assertEquals("date", expectedDate, actualDate);
Assert.assertEquals("user", expectedUser, actualUser);
Assert.assertEquals("action code", expectedActionCode, actualActionCode);
Assert.assertEquals("detail", expectedDetail, actualDetail);
}
}
 A Mock Logger object:
RemoteLogger log = new MockLogger();
app.setLogging(log);

THANK YOU!
Don.McGreal@ImprovingEnterprises.com
@donmcgreal
linkedin.com/in/donmcgreal

www.synerzip.com38
Questions?
www.synerzip.com
Hemant Elhence
hemant@synerzip.com
469.322.0349
www.synerzip.com

www.synerzip.com39 3939
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Adopting TDD - by Don McGreal

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