Introduction To UnitTesting & JUnit

Introduction to
UNIT TESTING & JUNIT
By:
DHEERAJ SHANDILYA
LinkedIn Id: http://in.linkedin.com/pub/dheeraj-shandilya/3a/77/5a2
Mindfire Solutions, India

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Introduction to Unit Testing
What, why and how to do Unit Testing
Framework that will help
Introduction & History of Junit
Reference & Questions
We are going to discuss
Lets play with basic codes
Annotations and assertions in Junit

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What is Unit Testing?
A Unit is the smallest possible part of application/system under test.
Testing is a process of checking/evaluating an attribute/characteristics
/capability of a program/object/method/application/..... and determine
that actual behavior meets with expected behavior.
Unit Testing is a process of writing test for specific part of code/system.
Unit testing help us reduce the number of bugs, time spent on debugging,
create a stable and reliable application.

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What is Unit Testing?
Static Analysis
Static unit testing offers the minimum path coverage
It helps in checking structural properties of code
Here we check syntax, unreachable codes,
undeclared/uninitialized variable, parameter type mismatch...
Dynamic Analysis
Dynamic unit testing detects control and data flow problems
It helps in checking the behavior of unit source code on test
data
Here we will check classes, methods, boundary condition,
logic errors...

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1. If a unit is not working, it affects performance of complete system
For example
Consider any system say bike, car, mobile, human being anything.
Suppose mobile screen (lcd/led) is not working then you will not
be able to see menu over screen. Hence you can not work/operate.
Why to do Unit Testing?

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2.There is strength in unity but not in unit.
It means with unit testing we can detect defect and fix bugs easily.
For example
Police interrogate suspects individually to get some more clues.
If different component/unit of a system works fine, then there are
More possibility that system (combining all component) will also
work fine

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Easy to detect defect and debug

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Benefits of Unit Testing?
> It Saves time on debugging. Hence effort and money too.
> It prepares the base for further testing like integration, functional
Testing...
> It enhances performance and provide obstacle free control.
> It ensures repeatability of desired behavior
> Unit Testing makes it easier to change and refactor code.
> Unit Testing inspires confidence.
> Unit Testing reduces the level of bugs in production code.
> We will get instant feedback
> It brings modularity in design

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How to do Unit Testing
We have to write tests to check that the functionality of a unit,
often a class(or function/methods in the class) meet its
requirement.
Tests are written as the unit is developed.
So this testing is done by software engineer while development
The idea is that every time you make a change to the unit you
rerun the tests and see if your change has broken anything.
There are many tools and framework that will help us in unit
testing.

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For different technology we can use different unit testing
framework. For example
Java: JUnit, TestNG...
C: Ctest, Cunit, Opmock ...
Python: Unittest, Py.test, Nose...
Visual Basic(VB6.0): vbunit, vbaunit, TinyUnit...
PHP: PHPunit, SnapTest ...
We can see complete list here
http://en.wikipedia.org/wiki/List_of_unit_testing_frameworks
Tools & Framework

Introduction to Junit
JUnit: It is a framework for performing unit testing of Java programs.
It is used to write repeatable tests. For this we need Eclipse IDE. .
Eclipse contains a base workspace and an extensible plug-in system for
customizing the environment. It is used to develop application in various
languages...
JUnit is linked as a JAR at compile-time.
The framework resides under package junit.framework for JUnit 3.8 and
earlier, and under package org.junit for JUnit 4 and later.

History of Junit
1994
Sunit came
into existence
1997
Initiation
of Junit
2000
Junit Officially
Released
2002
Eclipse came
into existence

@Test
public void method()
The @Test annotation identifies a method as a test method.
@Test (expected = Exception.class)
Fails, if the method does not throw the named exception.
@Test (timeout=time in millisec)
Fails, if the method/test timed out after specified time
@Ignore
Ignores the test method.
This is useful when the underlying code has been changed and the test case
has not yet been adapted. Or if the execution time of this test is too long to
be included.
Annotations in Junit

@Before
This method is executed before each test. It is used to prepare the test environment
(e.g. read input data, initialize the class).
@After
This method is executed after each test. It is used to cleanup the test environment
(e.g. delete temporary data, restore defaults). It can also save memory by cleaning
up expensive memory structures.

@BeforeClass
public static void method()
This method is executed once, before the start of all tests.
It is used to perform time intensive activities, for example to connect to a database.
Methods annotated with this annotation need to be defined as static to work with JUnit.
@AfterClass
public static void method()
This method is executed once, after all tests have been finished.
It is used to perform clean-up activities, for example to disconnect from a database.
Methods annotated with this annotation need to be defined as static to work with JUnit.

.
There are several Juint Assertion methods .
These are static methods defined in
org.junit.Assert class
An assertion is a statement of expected
outcome. In other words, it is the expected
result of your test.
Assert Method

Assert Method
Most common of them are
> Fail() - Fails test
> assertNotNull(0) /assertNull(0) - assert if object is (not) null
> assertFalse(b) /assertTrue(b) - asserts if b is false /true
> assertEquals(a, b) - Compares two objects using equals() method
> assertArrayEquals(a, b) - compares two arrays

Lets do some basic testing in Eclipse IDE

Best Practices In Unit Testing
Isolate test from other environment, classes, tests.
Self Descriptive
> Name of variable, classes, methods......
Avoid conditional logics(if else...), nested loops
Use various assertion method provided by framework.
> Assertion message should tell the problem. One can include business logics,
Separate the test based on type and business module

http://junit.sourceforge.net/javadoc/org/junit/Assert.html
Http://www.pluralsight.com
Http://www.youtube.com
Http://en.wikipedia.org/
Http://junit.org
Http://www.google.co.in
Credit goes to ...

Introduction To UnitTesting & JUnit

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