An Introduction to Unit Test Using NUnit

An Introduction to Unit Test
Using NUnit
Wei Li
08/2007

Test, Test and More Test
• Developer Test
o Unit Test
o Integration Test
o Regression Test

• QA Test
o Integration Test
o Regression Test
o Performance Test
o Stress Test

• Customer/User Test
o Acceptability Test
o 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 Test
Sit In Life Cycle
• Requirement Gathering
• Business System Design
• Technical Design
o Architecture Design
o Technical System Design
• Construction
o Code and Unit Test
• QA Test
• User Test

Unit Test Is Not
• QA test

• Customer/user test

Why Unit Test
• What? Write code to test code?

• Why?

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

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

• 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

• Debugger test

Problems With The Above
Methods
• Is the test well structured?
• Can it be automated?
• 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

• 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 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]
• Used to indicate a tear down method should be ran after each
of the tests are ran

Example: Test2.cs

– [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

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

– [Ignore(“Not ready yet")]

Example: Test4.cs

NUnit Assertion
• It is all unit test cares about

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

• Assertion failure means test failure

NUnit Assertion
• Equality Asserts
• Identity Asserts
• Comparison Asserts
• Type Asserts
• Condition tests
• Utility methods

NUnit Equal Assertion
• Assert.AreEqual(expected, real_value)
• Assert.AreEqual(expected, real_value,
“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”)

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

NUnit Condition Assertion
• Assert.IsTrue()
• Assert.IsFalse()
• Assert.IsNull()
• Assert.IsNotNull()
• Assert.IsEmpty()
• Assert.IsNotEmpty()

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
• 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
• 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

An Introduction to Unit Test Using NUnit

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