Applying Unit Tests & Test-Driven Development€¦ · Applying Unit Tests & Test-Driven Development...

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Applying Unit Tests &Test-Driven Development

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@donmcgreal

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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 TestingTest 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 - Traditionalpublic 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...


The Plan...

Unit Testing




Q&A



Start Here


Think

Test

Code

Design

2-10 Minutes

TDD Mantra


RefactorGreen

RedThink

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.


RefactorGreen

RedThink

Test

Code

Design

2-10 Minutes

TDD Mantra


TDD lets you know when...

Y aA i n ’ tG o n n aN e e dI t !


“Only write code to fix a failing test”

So...


Case StudyEmpirical 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...


The Plan...

Unit Testing




Q&A


Unit Testing - Traditionalpublic 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 - BDD Stylepublic 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

VerifyassertEquals(expected, actual);assertFalse(condition);assertTrue(condition);assertNull(object);assertNotNull(object);assertSame(expected, actual);assertNotSame(unexpected, actual);fail();

Teardown



Forget about Tests; Think about Specificationsit’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 Behaviorsworry 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 Plan...

Unit Testing




Q&A


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):booleancredit(amt):boolean

SoaBankJmsBank FakeBank

Dependency Injection

bank





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

ClientApp app = new ClientApp();RemoteLogger log = new FakeLogger();app.setLogging(log); boolean success = app.debit(1000);




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


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:

ClientApp app = new ClientApp();RemoteLogger log = new MockLogger();app.setLogging(log); boolean success = app.debit(1000);




The Plan...

Unit Testing




Q&A


THANK [email protected]

@donmcgreal

linkedin.com/in/donmcgreal



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Questions?

www.synerzip.com Hemant Elhence

[email protected]

www.synerzip.com

www.synerzip.com39 3939

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