an introduction to unit test using nunit

An Introduction to Unit Test Using NUnitUsing NUnit

Wei Li

08/2007

Test, Test and More Test

• Developer Testo Unit Testo Integration Testo Regression Test

• QA Test• QA Testo Integration Testo Regression Testo Performance Testo Stress Test

• Customer/User Testo Acceptability Testo Useability Test

What Is Unit Test

• Self checking or validation to ensure your code works as expected

• Developer’s test

• Part of the construction cycle

Where Does Unit TestSit In Life Cycle

• Requirement Gathering

• Business System Design

• Technical Design

o Architecture Designo

o Technical System Design

• Construction

oCode and Unit Test• QA Test

• User Test

Unit Test Is Not

• QA test

• Customer/user test• Customer/user test

Why Unit Test

• What? Write code to test code?

• Why?• Why?

Instant Feedback

• Unit test provides the earliest opportunity to identify and fix a defect

• The earlier a defect is caught, the less • The earlier a defect is caught, the less expensive it is to fix it

• Done before integration

• Like a dedicated QA/user sits next to you and test your code immediately

Help Design And Write Better Code

• If your code is hard to be unit tested, how can it be easily used, maintained and extended?extended?

Regression Checker

• When new release of the external dependency comes, you can quickly run the unit tests to make certain the new release won’t break your system

• Automatic change detector – When changes are made to the code, automated unit

tests ensure that the change does not break something somewhere

Good Way To Work On Legacy Code

• Write unit test to get started with legacy code

Good Way To Learn New Language and New API

• Write unit test cases to learn and try new API

• Your unit test cases become reusable knowledge base

Good For Reporting a Defect

• Write a test case to report a defect or bug in a system

• When something fails, writing a unit test for that failure guarantees that it's fixed for once and for all.

Save Time In Long Term

• Unit test is reusable and repeatable

• Unit test can be automated• Unit test can be automated

• Write once run forever

There Is More Than One Way To Do It

• Main() method with lots of print out

• GUI “push that button” test• GUI “push that button” test

• Debugger test

Problems With The Above Methods

• Is the test well structured?

• Can it be automated?

• Is the test repeatable?• Is the test repeatable?

• Does it need human interaction?

• Is it easy to be maintained ?

• How to present test results?

Stop Debugger Test

• Debugger time is not recyclable

• Debugger session is not reusable by others• Debugger session is not reusable by others

• Not a regression testing tool

• Mental assertion is error-prone and boring

Enter NUnit

• A unit test framework written in C#

• It uses attributes to identify unit test fixtures

• It uses assertions for verification• It uses assertions for verification

• It can be used to test any .NET code, not just C#

• It provides a console and GUI interface

• It can be integrated into VS.NET

How Does NUnit Test Code Look Like?

• Show me the code

NUnit Attributes

• Custom attribute injects more information to your class at compilation time

• NUnit uses it to mark and identify unit test fixture

NUnit Required Attributes

– [TestFixture]• Used to indicate that a class contains test methods

– [Test]• Used to indicate that a method within a test fixture

should be run by the Test Runner application

Example: Test1.cs

NUnit Optional Attributes

– [SetUp] • Used to indicate a setup method should be ran before each of

the tests

– [TearDown] – [TearDown] • Used to indicate a tear down method should be ran after each

of the tests are ran

Example: Test2.cs

NUnit Optional Attributes

– [TestFixtureSetUp]• Used to indicate a setup method that will be ran once; before

all other tests. This is the first method that is called before the tests are started.

– [TestFixtureTearDown]• Used to indicate a tear down method that will be ran once;

after all other tests have run. This is the last method that is called after all the tests have finished.

Example: Test3.cs

NUnit Optional Attributes

– [ExpectedException(typeof(Exception))] • When you want an exception to be thrown• Will only pass if exception type was thrown

– [Ignore(“Not ready yet")]– [Ignore(“Not ready yet")]

Example: Test4.cs

NUnit Assertion

• It is all unit test cares about

• NUnit provides a full set of assertions ready • NUnit provides a full set of assertions ready to be used

• Assertion failure means test failure

NUnit Assertion

• Equality Asserts

• Identity Asserts

• Comparison Asserts• Comparison Asserts

• Type Asserts

• Condition tests

• Utility methods

NUnit Equal Assertion

• Assert.AreEqual(expected, real_value)

• Assert.AreEqual(expected, real_value, “a message”)“a message”)

• Assert.AreNotEqual(expected, real_value)

• Assert.AreNotEqual(expected, real_value, “a message”)

NUnit Identity Assertion

• Assert.AreSame(expected, real_value)

• Assert.AreSame (expected, real_value, “a message”)“a message”)

• Assert.AreNotSame (expected, real_value)

• Assert.AreNotSame (expected, real_value, “a message”)

NUnit Condition Assertion

• Assert.IsTrue()

• Assert.IsFalse()

• Assert.IsNull()• Assert.IsNull()

• Assert.IsNotNull()

• Assert.IsEmpty()

• Assert.IsNotEmpty()

Examples

Show me the code

Test Driven/Test First Development

• Write a unit test case for a new functionality

• Run the unit test and it will fail

• Write just enough code to make the test pass• Write just enough code to make the test pass

• Run the unit test again and it passes

• Refactory the code to make it better

• Repeat the unit test

• Repeat the cycle

Continuous Integration

• Get the latest version of the project from source control system

• Build/compile the code• Run all unit test cases• Run all unit test cases• Publish the build and test results• Notify the development team for any failure• Repeat the process periodically, for example, once

every hour

Continuous Integration

• Demo: using NAnt to build solution, run test cases, generate test result reports

Questions?

Happy Testing!