JUnit Kung Fu: Getting More Out of Your Unit Tests

JUnit Kung Fu
Getting more out of your unit tests

John Ferguson Smart
Principle Consultant
Wakaleo Consulting

So who is this guy, anyway?
John Ferguson Smart
Consultant, Trainer, Mentor, Author, Speaker

So who is this guy, anyway?
John Ferguson Smart
Consultant, Trainer, Mentor, Author,...

Agenda
What will we cover today
Naming your tests
Hamcrest Assertions and Matchers
Parameterized tests and JUnit Theories
JUnit Rules
Parallel Testing
JUnit Categories
Continuous Testing
Mockito

Anatomy of a JUnit 4 test
What’s the big deal with JUnit 4?
import static com.wakaleo.gameoflife.domain.Cell.DEAD_CELL;
import static com.wakaleo.gameoflife.domain.Cell.LIVE_CELL;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import org.junit.Test; No need to extend TestCase

public class WhenYouCreateACell {
Annotation-based
@Test
public void aLiveCellShouldBeRepresentedByAnAsterisk() {
Cell cell = Cell.fromSymbol("*");
assertThat(cell, is(LIVE_CELL));
}
Call the tests anything you want

@Ignore("Pending Implementation")
@Test Annotations for test metadata
public void aDeadCellShouldBeRepresentedByADot() {
Cell cell = Cell.fromSymbol(".");
assertThat(cell, is(DEAD_CELL));
}
...
}

What’s in a name
Name your tests well

"What's in a name? That which we call a rose
By any other name would smell as sweet."
Romeo and Juliet (II, ii, 1-2)

What’s in a name
The 10 5 Commandments of Test Writing
I. Don’t say “test, say “should” instead
II. Don’t test your classes, test their behaviour
III. Test class names are important too
IV. Structure your tests well
V. Tests are deliverables too

What’s in a name
Don’t use the word ‘test’ in your test names

testBankTransfer()

testWithdraw()

testDeposit()

What’s in a name
Do use the word ‘should’ in your test names

testBankTransfer()

testWithdraw()
tranferShouldDeductSumFromSourceAccountBalance()

testDeposit()
transferShouldAddSumLessFeesToDestinationAccountBalance()

depositShouldAddAmountToAccountBalance()

What’s in a name
Your test class names should represent context

When is this behaviour applicable?

What behaviour are we testing?

What’s in a name
Write your tests consistently
‘Given-When-Then’ or ‘Arrange-Act-Assert’ (AAA)
@Test
public void aDeadCellWithOneLiveNeighbourShouldRemainDeadInTheNextGeneration() {
String initialGrid = "...n" +
".*.n" + Prepare the test data (“arrange”)
"...";

String expectedNextGrid = "...n" +
"...n" +
"...n"; Do what you are testing (“act”)
Universe theUniverse = new Universe(seededWith(initialGrid));

theUniverse.createNextGeneration();
String nextGrid = theUniverse.getGrid();
Check the results (“assert”)
assertThat(nextGrid, is(expectedNextGrid));
}

What’s in a name
Tests are deliverables too - respect them as such
Refactor, refactor, refactor!
Clean and readable

Express Yourself with Hamcrest
Why write this...
import static org.junit.Assert.*;
...
assertEquals(10000, calculatedTax, 0);

when you can write this...
import static org.hamcrest.Matchers.*;
...
assertThat(calculatedTax, is(10000));

“Assert that are equal 10000 and calculated tax (more or less)” ?!

Don’t I just mean “assert that calculated tax is 10000”?

With Hamcrest, you can have your cake and eat it!

assertThat(calculatedTax, is(expectedTax));

Readable asserts

String color = "red";
assertThat(color, is("blue"));

Informative errors

String[] colors = new String[] {"red","green","blue"};
String color = "yellow";
assertThat(color, not(isIn(colors)));
Flexible notation

More Hamcrest expressiveness
String color = "red";
assertThat(color, isOneOf("red",”blue”,”green”));

List<String> colors = new ArrayList<String>();
colors.add("red");
colors.add("green");
colors.add("blue");
assertThat(colors, hasItem("blue"));

assertThat(colors, hasItems("red”,”green”));

assertThat(colors, hasItem(anyOf(is("red"), is("green"), is("blue"))));

Home-made Hamcrest Matchers
Customizing and extending Hamcrest
Combine existing matchers
Or make your own!

Customizing Hamcrest matchers
You can build your own by combining existing Matchers...

Create a dedicated Matcher for the Stakeholder class

List stakeholders = stakeholderManager.findByName("Health");
Matcher<Stakeholder> calledHealthCorp = hasProperty("name", is("Health Corp"));
assertThat(stakeholders, hasItem(calledHealthCorp));

Use matcher directly with hasItem()

“The stakeholders list has (at least) one item with
the name property set to “Health Corp””

Writing your own matchers in three easy steps!
public class WhenIUseMyCustomHamcrestMatchers {
@Test
public void thehasSizeMatcherShouldMatchACollectionWithExpectedSize() {
List<String> items = new ArrayList<String>();
items.add("java");
assertThat(items, hasSize(1));
}
}
We want something like this...

I want a matcher that checks the size of a collection

public class HasSizeMatcher extends TypeSafeMatcher<Collection<? extends Object>> {
private Matcher<Integer> matcher;
Extend the TypeSafeMatcher class
public HasSizeMatcher(Matcher<Integer> matcher) {
this.matcher = matcher; Provide expected values in
} the constructor

public boolean matchesSafely(Collection<? extends Object> collection) {
return matcher.matches(collection.size());
} Do the actual matching
public void describeTo(Description description) {
description.appendText("a collection with a size that is");
matcher.describeTo(description);
} Describe our expectations
}

So let’s write this Matcher!

import java.util.Collection;
import org.hamcrest.Factory;
import org.hamcrest.Matcher;

public class MyMatchers { Use a factory class to store your matchers

@Factory
public static Matcher<Collection<? extends Object>> hasSize(Matcher<Integer> matcher){
return new HasSizeMatcher(matcher);
}
}

All my custom matchers go in a special Factory class

import static com.wakaleo.gameoflife.hamcrest.MyMatchers.hasSize;
import static org.hamcrest.MatcherAssert.assertThat;

public class WhenIUseMyCustomHamcrestMatchers {

@Test
public void thehasSizeMatcherShouldMatchACollectionWithExpectedSize() {
items.add("java");
assertThat(items, hasSize(1));
}
}

Hamcrest-style error messages

But wait! There’s more!
@Test
public void weCanUseCustomMatchersWithOtherMatchers() {
items.add("java");
assertThat(items, allOf(hasSize(1), hasItem("java")));
}
Combining matchers

@Test
public void weCanUseCustomMatchersWithOtherMatchers() {
items.add("java");
items.add("groovy");
assertThat(items, hasSize(greaterThan(1)));
}
Nested matchers

Data-Driven Unit Tests
Using Parameterized Tests

Parameterized tests - for data-driven testing
Take a large set of test data, including an expected result
Deﬁne a test that uses the test data
Verify calculated result against expected result
{2, 0, 0}
{2, 1, 2}
{2, 2, 4}
{2, 3, 6}
{2, 4, 8}
x=a*b
{2, 5, 10}
Test
{2, 6, 12}
{2, 7, 14}
... Verify
Data

Parameterized tests
Example: Calculating income tax

Parameterized tests with JUnit 4.8.1 Income Expected Tax
$0.00 $0.00
What you need: $10,000.00 $1,250.00
Some test data $14,000.00 $1,750.00
$14,001.00 $1,750.21
A test class with matching ﬁelds $45,000.00 $8,260.00
$48,000.00 $8,890.00
And some tests $48,001.00 $8,890.33
$65,238.00 $14,578.54
And an annotation $70,000.00 $16,150.00
public class TaxCalculatorDataTest {
@RunWith(Parameterized.class) $70,001.00 $16,150.38
public classdouble income;
private TaxCalculatorDataTest {
$80,000.00 $19,950.00
private double expectedTax;
income;
private double expectedTax; $100,000.00 $27,550.00
public TaxCalculatorDataTest(double income, double expectedTax) {
super();
this.income = income;
public TaxCalculatorDataTest(double income, double expectedTax) {
this.expectedTax = expectedTax;
super();
} this.expectedTax = expectedTax;
} } this.expectedTax = expectedTax;
}
@Test
public void shouldCalculateCorrectTax() {...}
@Test
} public void shouldCalculateCorrectTax() {...}
}

This is a parameterized test
How it works Income Expected Tax
@RunWith(Parameterized.class) $0.00 $0.00
public class TaxCalculatorDataTest { The @Parameters annotation $10,000.00 $1,250.00
private double income;
private double expectedTax;
indicates the test data $14,000.00 $1,750.00
@Parameters $14,001.00 $1,750.21
public static Collection<Object[]> data() { $45,000.00 $8,260.00
return Arrays.asList(new Object[][] {
{ 0.00, 0.00 }, $48,000.00 $8,890.00
{ 10000.00, 1250.00 }, { 14000.00, 1750.00 }, $48,001.00 $8,890.33
{ 14001.00, 1750.21 }, { 45000.00, 8260.00 },
{ 48000.00, 8890.00 }, { 48001.00, 8890.33 }, $65,238.00 $14,578.54
{ 65238.00, 14578.54 }, { 70000.00, 16150.00 },
$70,000.00 $16,150.00
{ 70001.00, 16150.38 }, { 80000.00, 19950.00 },
{ 100000.00, 27550.00 }, }); $70,001.00 $16,150.38
}
$80,000.00 $19,950.00
public TaxCalculatorDataTest(double income, double expectedTax) { $100,000.00 $27,550.00
super();
this.expectedTax = expectedTax; The constructor takes the
} fields from the test data
@Test
public void shouldCalculateCorrectTax() {
TaxCalculator calculator = new TaxCalculator(); The unit tests use data
double calculatedTax = calculator.calculateTax(income);
assertThat(calculatedTax, is(expectedTax)); from these fields.
}
}

Parameterized Tests in Eclipse Income Expected Tax
$0.00 $0.00
Run the test only once $10,000.00 $1,250.00

Eclipse displays a result for each data set $14,000.00
$14,001.00
$1,750.00
$1,750.21
$45,000.00 $8,260.00
$48,000.00 $8,890.00
$48,001.00 $8,890.33
$65,238.00 $14,578.54
$70,000.00 $16,150.00
$70,001.00 $16,150.38
$80,000.00 $19,950.00
$100,000.00 $27,550.00

Example: using an Excel Spreadsheet

@Parameters
public static Collection spreadsheetData() throws IOException {
InputStream spreadsheet = new FileInputStream("src/test/resources/aTimesB.xls");
return new SpreadsheetData(spreadsheet).getData();
}

Example: testing Selenium 2 Page Objects
A Page Object class

public class ExportCertificateSubmissionFormPage extends WebPage {

@FindBy(name="HD_EN") WebElement importerName;
@FindBy(name="HD_EA") WebElement importerAddress;
@FindBy(name="HD_ER") WebElement importerRepresentative;
...
public String getImporterName() {
return importerName.getValue();
}

public void setImporterName(String value) {
enter(value, into(importerName));
}
...
}


Testing the fields using a parameterized test

@Parameters
public static Collection<Object[]> data() {
return Arrays.asList(new Object[][] {
{ "importerName", "an-importer-name" },
{ "importerAddress", "an-importer-address" },
{ "importerRepresentative", "a-importer-representative" },
...
});
}


Setting up the test data
private String field;
private String inputValue;

public ReadingAndWritingFieldsWhenRaisingACertificate(String field,
String inputValue) {
this.field = field;
this.inputValue = inputValue;
}


Test reading and writing to/from the field

@Test
public void userShouldBeAbleToWriteToAnInputFieldAndThenReadTheValue() {
setFieldValueUsing(setterFor(field));

String retrievedValue = getFieldValueUsing(getterFor(field));

assertThat(retrievedValue, is(inputValue));
} (Reflection magic goes here)

JUnit Rules
Using Existing and Custom JUnit Rules
Customize and control how JUnit behaves

JUnit Rules
The Temporary Folder Rule
public class LoadDynamicPropertiesTest {
Create a temporary folder
@Rule
public TemporaryFolder folder = new TemporaryFolder();

private File properties;

@Before Prepare some test data
public void createTestData() throws IOException {
properties = folder.newFile("messages.properties");
BufferedWriter out = new BufferedWriter(new FileWriter(properties));
// Set up the temporary file
out.close();
}
Use this folder in the tests

@Test
public void shouldLoadFromPropertiesFile() throws IOException {
DynamicMessagesBundle bundle = new DynamicMessagesBundle();
bundle.load(properties);
// Do stuff with the temporary file
}
}
The folder will be deleted afterwards

JUnit Rules
The ErrorCollector Rule
Report on multiple error conditions in a single test
public class ErrorCollectorTest {

@Rule
public ErrorCollector collector = new ErrorCollector();

@Test Two things went wrong here
public void testSomething() {
collector.addError(new Throwable("first thing went wrong"));
collector.addError(new Throwable("second thing went wrong"));
String result = doStuff();
collector.checkThat(result, not(containsString("Oh no, not again")));
}

Check using Hamcrest matchers
private String doStuff() {
return "Oh no, not again";
}
}

JUnit Rules
The ErrorCollector Rule
Report on multiple error conditions in a single test
public class ErrorCollectorTest {

@Rule All three error messages are reported
public ErrorCollector collector = new ErrorCollector();

@Test
collector.addError(new Throwable("first thing went wrong"));
collector.addError(new Throwable("second thing went wrong"));
String result = doStuff();
collector.checkThat(result, not(containsString("Oh no, not again")));
}

private String doStuff() {
return "Oh no, not again";
}
}

JUnit Rules
The Timeout Rule
Deﬁne a timeout for all tests
public class GlobalTimeoutTest {

@Rule
public MethodRule globalTimeout = new Timeout(1000);

@Test No test should take longer than 1 second
for(;;);
}
Oops
@Test
public void testSomethingElse() {
}
}

JUnit Rules
The Veriﬁer Rule
Adding your own custom veriﬁcation logic
public class VerifierTest {

private List<String> systemErrorMessages = new ArrayList<String>();

@Rule
public MethodRule verifier = new Verifier() {
@Override
public void verify() { After each method, perform this check
assertThat(systemErrorMessages.size(), is(0));
}
};

@Test
// ...
systemErrorMessages.add("Oh, bother!");
}
}

JUnit Rules
The Watchman Rule
Keeping an eye on the tests
public class WatchmanTest {
private static String watchedLog;

@Rule
public MethodRule watchman = new TestWatchman() { Called whenever a test fails
@Override
public void failed(Throwable e, FrameworkMethod method) {
watchedLog += method.getName() + " " + e.getClass().getSimpleName() + "n";
}

@Override
public void succeeded(FrameworkMethod method) {
watchedLog += method.getName() + " " + "success!n";
}
};
Called whenever a test succeeds
@Test
public void fails() {
fail();
}
@Test
public void succeeds() {...}
}

JUnit Categories
Grouping tests
Distinguish different types of tests
Mark tests using an annotation
Run different categories of test in
different test suites

JUnit Categories
Setting up JUnit Categories
1) Deﬁne some categories
Categories are defined as interfaces
public interface IntegrationTests {}

public interface PerformanceTests {}

public interface PerformanceTests extends IntegrationTests {}

Subclassing works too

JUnit Categories
2) Annotate your tests
public class CellTest {
A test with a category
@Category(PerformanceTests.class)
@Test
public void aLivingCellShouldPrintAsAPlus() {...}

@Category(IntegrationTests.class)
@Test A test with several
public void aDeadCellShouldPrintAsAMinus() {...} categories

@Category({PerformanceTests.class,IntegrationTests.class})
@Test
public void thePlusSymbolShouldProduceALivingCell() {...} A normal test
@Test
public void theMinusSymbolShouldProduceADeadCell() {...}
}

JUnit Categories
2) Or annotate your class
You can also annotate the class
@Category(IntegrationTests.class)
public class CellTest {

@Test
public void aLivingCellShouldPrintAsAPlus() {...}

@Test
public void aDeadCellShouldPrintAsAMinus() {...}

@Test
public void thePlusSymbolShouldProduceALivingCell() {...}

@Test
public void theMinusSymbolShouldProduceADeadCell() {...}
}

JUnit Categories
3) Set up a test suite
import org.junit.experimental.categories.Categories;
import org.junit.experimental.categories.Categories.IncludeCategory;
import org.junit.runner.RunWith;
import org.junit.runners.Suite.SuiteClasses;

@RunWith(Categories.class) Run only performance tests
@IncludeCategory(PerformanceTests.class)
@SuiteClasses( { CellTest.class, WhenYouCreateANewUniverse.class })
public class PerformanceTestSuite {
Still need to mention the test classes
}

JUnit Categories
3) Set up a test suite - excluding categories

@RunWith(Categories.class)
@RunWith(Categories.class) Don’t run performance tests
@IncludeCategory(PerformanceTests.class)
@ExcludeCategory(PerformanceTests.class)
public class PerformanceTestSuite {
public class UnitTestSuite {

}
}

Parallel tests
Running tests in parallel
Run your tests faster
Also works well with multi-core CPUs
Results vary depending on the tests
IO
Database
...

Parallel tests
Setting up parallel tests with JUnit and Maven
<project...> Needs Surefire 2.5
<plugins>
...
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.5</version>
<configuration> ‘methods’, ‘classes’, or ‘both’
<parallel>methods</parallel>
</configuration>
</plugin>
</plugins>
...
<build>
<dependencies>
<dependency> Needs JUnit 4.8.1 or better
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</build>
...
</project>

Continuous Testing
Continuous Tests with Inﬁnitest
Inﬁnitest is a continuous test tool for Eclipse and IntelliJ
Runs your tests in the background when you save your code

Continuous Testing
Using Inﬁnitest
Whenever you save your ﬁle changes, unit tests will be rerun

Failing test
Project containing an error

Error message about the failed test

Mocking with style
Mockito - lightweight Java mocking

Account
balance
number
getFees(feeType)
import static org.mockito.Mockito.*;
....
Account accountStub = mock(Account.class);
when(accountStub.getFees(FeeType.ACCOUNT_MAINTENANCE)).thenReturn(4.00);
when(accountStub.getFees(FeeType.TRANSACTION_FEE)).thenReturn(0.50);

assertThat(accountStub.getFees(FeeType.TRANSACTION_FEE), is(0.50));

Low-formality mocking

Mocking with style
AccountDao
createNewAccount(String id)

AccountDao accountDao = mock(AccountDao.class);
Account newAccount = mock(Account.class);
when(accountDao.createNewAccount(123456)).thenReturn(newAccount)
.thenThrow(new AccountExistsException() );

Manage successive calls

Mocking with style
AccountDao

@Mock private AccountDao accountDao
...

Mockito annotations

Mocking with style
Account
balance
number
getEarnedInterest(year)

when(accountStub.getEarnedInterest(intThat(greaterThan(2000)))).thenReturn(10.00);

Use matchers

Mocking with style
AccountDao

@Mock private AccountDao accountDao
...
// Test stuff
...
verify(accountDao).createNewAccount( (String) isNotNull());

Verify interactions

Thanks for your attention

John Ferguson Smart
Email: john.smart@wakaleo.com
Web: http://www.wakaleo.com
Twitter: wakaleo

JUnit Kung Fu: Getting More Out of Your Unit Tests

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