Transcript JUnit, - Rochester Java User`s Group

Java Unit
Mark Mosher
[email protected]
Rochester Java Users Group
April 12, 2016
EMBEDDED REAL-TIME, INC.
http://www.emrt.com
Agenda
Unit Testing Principles
 Benefits of Unit Testing
 Java Unit History and Philosophy
 The JUnit Framework
 Testing Your Classes
 Deployment Guidelines
 Summary
Q & A

April 12, 2016
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Unit Testing Principles
Who? Developers, testing their own code
 When? During implementation.
 What? White box testing of “modules” classes in our case.
 How? Test normal and boundary inputs
against expected results.
 Why? A great way to test an API.

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Quantitative Benefits
Objective: Pass/Fail.
 Repeatable: Retest after a change to
verify no unintended side effects.
 Measurable: Can count the number of
tests that pass/fail.
 Bounded: Narrow focus simplifies finding
and fixing defects.
 Cheaper: Find and fix defects early

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Qualitative Benefits
Assessment-oriented: Writing the unit test
forces us to deal with design issues cohesion, coupling.
 Confidence-building: Know what works.
Also easier to change when it’s easy to
retest.

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Java Unit History
Roots in eXtreme Programming
 Kent Beck: Smalltalk Test Framework
 Erich Gamma: Design Patterns
 Wrote JUnit on plane to OOPSLA ‘97
 Description appeared in July 1998 Java
Report.
 Available on XP web site.
 Other frameworks (C++, Python, VB…)

April 12, 2016
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Assumptions & Goals
Assumption: If a feature lacks an
automated test, it doesn’t work.
 Goal #1: Make it easy for developers to
write tests.
 Goal #2: Make it easy to create tests that
retain their value over time.
 Goal #3: Make it easy to leverage existing
tests to create new ones.

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The Java Unit Framework
Test
 TestCase
 TestResult
 TestSuite
 Assertions
 TestRunner

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junit.framework.Test
Public interface
 Defines one method: run(testResult)
 Component in Composite Pattern
 Implemented by TestCase (Leaf in
Composite pattern)
 Implemented by TestSuite (applies
Composite, maintains a collection of tests)

April 12, 2016
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junit.framework.TestCase
Applies the Command pattern - create an
object and give a method “execute” - run.
 Implements the run() Template method.
 Defines abstract setUp, runTest and
tearDown methods.
 This is the main class to extend for your
unit tests.

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junit.framework.TestResult
Applies the Collecting Parameter pattern collects the results of running tests.
 Counts number of tests run.
 Counts failures - thrown
AssertionFailedExceptions.
 Counts errors - All other Throwables.

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junit.framework.TestSuite
Defines addTest(Test) method.
 Along with TestCase, implements the Test
interface (run method). Allows suites of
test suites.
 Adds convenience constructor public static
Test suite() uses reflection to find the
testing methods.

April 12, 2016
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Assertions
Provided by TestCase.
 Define pass/fail criteria - a must!
 assert(boolean)
 assert(String,boolean)
 assertEquals(Object,Object)
 assertEquals(String,Object,Object)
 fail()
 fail(String)

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junit.*ui.TestRunner

Three versions
– java.textui.TestRunner
– java.ui.TestRunner
– java.swingui.TestRunner
GUI (ui or swingui) good for developing
single tests.
 Text (textui) faster for suites.

April 12, 2016
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Testing Your Classes

What to test
– Utility or Home object. Important or hard to
test any other way.
– Create test class, e.g. TestInteger to test the
Integer class.
– Have the test class extend
junit.framework.TestCase.
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Testing Your Classes, 2
Create one or more zero parameter
methods that start with “test”, e.g.
testInteger() and/or testParse().
 Junit will use reflection to execute these
automatically for you.
 Example IntegerTest...

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Deployment Guidelines
Have senior developer create and debug
the first unit test.
 Keep all unit tests in source control.
 Parallel test package branch, e.g.
test.lang.IntegerTest
 Create AllTests suite for each package,
then combine suites.
 Example test suite...

April 12, 2016
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Summary
Developer’s test tool - 100% Java
 Builds confidence in code base
 Eases refactoring risks & worry
 Quantitative results
 Qualitative benefits
 Free!

April 12, 2016
EMBEDDED REAL-TIME, INC.
http://www.emrt.com
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Where to find

Version 3.2 available at
www.xprogramming.com/software.htm
Source code
 Jar file
 Documentation & tutorials
 Javadoc

April 12, 2016
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