Transcript Unit testing Java program

Unit testing Java programs
Using JUnit 4
“If it isn't tested, it doesn’t work”
Unit testing Java programs
1
Testing
• Larman – a disciplin in UP
but very little in practice
• UPEDU
– description
Unit testing Java programs
2
The Unified Software Development
Process: Test procedure (V-model)
Start
Delivery
Requirement Specification
Program Design
Module Design
Accept Test
Integration Test
Module Test
Module Coding
Testing in XP – Module code Test
• Testing is an important discipline in XP (Extreme
Programming)
• XP idea: Create the test before the code to be
tested
– Writing the test makes you thing about detailed
design
• Test is an executable requirements
– Writing (and running) test will be a positive
experience.
– We know when a class is done
• When all tests run
Unit testing Java programs
4
Requirements for tests
• Tests must be executable
• A test must clearly show whether it
executed successfully or not
– The not-so-successful part of the test must
not be buried in a pile of test reports.
Unit testing Java programs
5
Which methods should be tested
• Test a method if you are not 100% sure
that the method is correct.
• Methods that usually does not need
testing
– Simple get and set methods
• However, you might call get and set methods in
testing other (more complex) methods
– Simple toString methods
Unit testing Java programs
6
The Unified Software Development
Process: Example testcase
Test
Step
Input/Action
Expected Output
Result
1
Create an account or look up an existing
one.
Use the apposite link to create a billing
event.
A billing event is created.
The account balance change
reflects the presence of the
new billing event
Account
balance: an
amount is not
shown in a
proper way.
Se
screen
shot
Test
Case 1.
Test cases - Example
• A property value of int between 2 and 9
Test
Case
Test value
expected
1
1 (before boundary)
rejected
2
2 (the boundary)
accepted
3
3 (after boundary)
accepted
4
8 (before boundary)
accepted
5
9 (the boundary)
accepted
6
10 (after boundary)
rejected
7
5 (some value in middle)
accepted
8
-3 (a negative number)
rejected
Unit testing Java programs
result
8
Do the exercise
Unit testing Java programs
9
Individual test cases
How to in JUnit
• Annotate the test method with
@org.junit.Test
– No need to extends any classes or use
special method names
• Unlike JUnit 3
• Generally you would like one test class pr.
Java class
– The unit to test is a class.
Unit testing Java programs
10
Fixtures: Before and After
• Sometimes you have 2 or more tests that must
run on the same data.
– To ease this JUnit introduces the concept of a “fixture”.
• You can annotate 2 methods in your test class
from
– @org.junit.Before
• Executed before each individual test
• Used to initialize test data
• Used quite often
– @org.junit.After
• Executed after each individual test
• Used to clean up after the test
– Examples: Close database or socket connections
• Not used very often
Unit testing Java programs
11
How to test exceptions
• JUnit 3: Testing an expected exception
try {
method();
fail(“Exception expected”);
}
catch (ExpectedException ex) { /* ignore */ }
• JUnit 4: Testing an expected exception
– Use an annotation
• @Test (expected = SomeException.class) public void
testMetod() { … }
• If testMethod() does not throw SomeException the test fails.
Unit testing Java programs
12
NetBeans assistance
• JUnit is a plugin to NetBeans
– And many other IDE’s
• NetBeans can assist you in making TestCases
for individual Java class and in assembling the
test cases into test suites.
– Right click the class you want to test
– Tools → JUnit tests
• Choose JUnit 4 (not JUnit 3)
– JUnit generates empty tests for each public /
protected method in a Java class.
– Fill you the empty tests and run the test.
• Like you run an ordinary program
Unit testing Java programs
13
References
Beck & Gamma JUnit Cookbook,
http://junit.sourceforge.net/doc/cookbook/cookbook.htm
Kent Beck & Erich Gamma invented JUnit
Martin Fowler Refactoring, Addison Wesley 2000
Chapter 4 Building Tests, page 89-102
Extreme Programming, Code the Unit Test First
http://www.extremeprogramming.org/rules/testfirst.html
Testing is an important discipline in XP (eXtreme Programming),
which is another Kent Bech invention.
Alex Garrett JUnit antipatterns
http://www-128.ibm.com/developerworks/opensource/library/os-junit
Unit testing Java programs
14