Tests Good Bad

Bad Tests, Good Tests

Tomek Kaczanowski

http://twitter.com/#!/devops_borat

Tomek Kaczanowski
• Developer
• Team lead
• Blogger
• http://kaczanowscy.pl/tomek
• Book author
• http://practicalunittesting.com

• Working at CodeWise (Krakow, Poland)
• ...we are hiring, wanna join us?

Why bother with tests?

• System works as expected

• Changes do not hurt

• Documentation

Tests help to achieve quality

Not sure when I saw this picture – probably
in GOOS?

What happens if we do it wrong?
• Angry clients
• Depressed developers

http://www.joshcanhelp.com

When I started out with unit tests, I was
enthralled with the promise of ease and
security that they would bring to my
projects. In practice, however, the
theory of sustainable software through
unit tests started to break down. This
difficulty continued to build up, until I
finally threw my head back in anger and
declared that "Unit Tests have become
more trouble than they are worth."
Llewellyn Falco and Michael Kennedy, Develop Mentor August 09

http://chrispiascik.com/daily-drawings/express-yourself/

write the right test

write this test right

Before we begin

• All of the examples are real but were:
• obfuscated
• to protect the innocents :)
• truncated
• imagine much more complex domain objects
• Asking questions is allowed
• ...but being smarter than me is not ;)

We don't need no stinkin' asserts!
public void testAddChunks() {
System.out.println("*************************************");
System.out.println("testAddChunks() ... ");
ChunkMap cm = new ChunkMap(3);
cm.addChunk(new Chunk("chunk"));

List testList = cm.getChunks("chunk",null);

if (testList.isEmpty())
fail("there should be at least one list!");
Chunk chunk = cm.getActualChunk("chunk",null);
if (chunk.getElements().isEmpty())
fail("there should be at least one element!");
if (cm.getFinalChunkNr() != 1)
fail("there should be at least one chunk!");
// iterate actual chunk
for (Iterator it = chunk.getElements().iterator();
it.hasNext();) {
Element element = (Element) it.next();
System.out.println("Element: " + element);
}
showChunks(cm);
System.out.println("testAddChunks() OK ");
} Courtesy of @bocytko

Success is not an option...

/**
* Method testFailure.
*/
public void testFailure() {
try {
Message message = new Message(null,true);
fail();
} catch(Exception ex) {
ExceptionHandler.log(ExceptionLevel.ANY,ex);
fail();
}
}

Courtesy of @bocytko

What has happened? Well, it failed...
public void testSimple() {
IData data = null;
IFormat format = null;
LinkedList<String> attr = new LinkedList<String>();
attr.add("A");
attr.add("B");

try {
format = new SimpleFormat("A");
data.setAmount(Amount.TEN);
data.setAttributes(attr);
IResult result = format.execute();
System.out.println(result.size());
Iterator iter = result.iterator();
while (iter.hasNext()) {
IResult r = (IResult) iter.next();
System.out.println(r.getMessage());
...
}
catch (Exception e) {
fail();
}
}

What has happened? Well, it failed...
public void testSimple() {
IData data = null;
IFormat format = null;
LinkedList<String> attr = new LinkedList<String>();
attr.add("A");
attr.add("B");data is null - ready or not,
NPE is coming! 
try {
format = new SimpleFormat("A");
data.setAmount(Amount.TEN);
data.setAttributes(attr);
IResult result = format.execute();
System.out.println(result.size());
Iterator iter = result.iterator();
while (iter.hasNext()) {
IResult r = (IResult) iter.next();
System.out.println(r.getMessage());
...
}
catch (Exception e) {
fail();
}
}

No smoke without tests
class SystemAdminSmokeTest extends GroovyTestCase {

void testSmoke() {

def ds = new org.h2.jdbcx.JdbcDataSource(
URL: 'jdbc:h2:mem:test;DB_CLOSE_DELAY=-1;MODE=Oracle',
user: 'sa', password: '')

def jpaProperties = new Properties()
jpaProperties.setProperty(
'hibernate.cache.use_second_level_cache', 'false')
jpaProperties.setProperty(
'hibernate.cache.use_query_cache', 'false')

def emf = new LocalContainerEntityManagerFactoryBean(
dataSource: ds, persistenceUnitName: 'my-domain',
jpaVendorAdapter: new HibernateJpaVendorAdapter(
database: Database.H2, showSql: true,
generateDdl: true), jpaProperties: jpaProperties)

…some more code below
}

No smoke without tests
class SystemAdminSmokeTest extends GroovyTestCase {

void testSmoke() {
// do not remove below code
// def ds = new org.h2.jdbcx.JdbcDataSource(
// URL: 'jdbc:h2:mem:test;DB_CLOSE_DELAY=-1;MODE=Oracle',
// user: 'sa', password: '')
//
// def jpaProperties = new Properties()
// jpaProperties.setProperty(
// 'hibernate.cache.use_second_level_cache', 'false')
// jpaProperties.setProperty(
// 'hibernate.cache.use_query_cache', 'false')
//
// def emf = new LocalContainerEntityManagerFactoryBean(
// dataSource: ds, persistenceUnitName: 'my-domain',
// jpaVendorAdapter: new HibernateJpaVendorAdapter(
// database: Database.H2, showSql: true,
// generateDdl: true), jpaProperties: jpaProperties)

…some more code below, all commented out :(
}

Let's follow the leader!

@Test
public class ExampleTest {

public void testExample() {
assertTrue(true);
}
}

Uh-oh, I feel lonely...

@Test
public class ExampleTest {

public void testExample() {
assertTrue(true);
}
}

Conclusions

• Automation!
• Running
• Verification
• Do not live with broken window
• And remember there is no one else to fix them but
you!
• It is a full time job!
• You should be informed why your test failed
• Master your tools
• …at least learn the basics!

Use of the real objects obscures the test
@Test
public void shouldGetTrafficTrend() {
//given
TrafficTrendProvider trafficTrendProvider
= mock(TrafficTrendProvider.class);
Report report = new Report(null, "", 1, 2, 3,
BigDecimal.ONE, BigDecimal.ONE, 1);
TrafficTrend trafficTrend = new TrafficTrend(report, report,
new Date(), new Date(), new Date(), new Date());
given(trafficTrendProvider.getTrafficTrend())
.willReturn(trafficTrend);
TrafficService service
= new TrafficService(trafficTrendProvider);

//when
TrafficTrend result = service.getTrafficTrend();

//then
assertThat(result).isEqualTo(trafficTrend);
}

Use of the real objects obscures the test
@Test
public void shouldGetTrafficTrend() {
//given
TrafficTrendProvider trafficTrendProvider
= mock(TrafficTrendProvider.class);
TrafficTrend trafficTrend = mock(TrafficTrend.class);
given(trafficTrendProvider.getTrafficTrend())
.willReturn(trafficTrend);

TrafficService service
= new TrafficService(trafficTrendProvider);

//when
TrafficTrend result = service.getTrafficTrend();

//then
assertThat(result).isEqualTo(trafficTrend);
}

Mock'em All!
@Test
public void shouldAddTimeZoneToModelAndView() {
//given
UserFacade userFacade = mock(UserFacade.class);
ModelAndView modelAndView = mock(ModelAndView.class);
given(userFacade.getTimezone()).willReturn("timezone X");

//when
new UserDataInterceptor(userFacade)
.postHandle(null, null, null, modelAndView);

//then
verify(modelAndView).addObject("timezone", "timezone X");
}

ModelAndView from
Mock'em All! SpringMVC – a mere
container for data, without
@Test any behaviour
//given
ModelAndView modelAndView = mock(ModelAndView.class);

//when

//then
verify(modelAndView).addObject("timezone", "timezone X");
}

Use the front door
@Test
//given
ModelAndView modelAndView = new ModelAndView();

//when
a pseudocode but that is
what we mean
//then
assertThat(modelAndView).contains("timezone", "timezone X");
}

Mock'em All!
Public class Util {

public String getUrl(User user, String timestamp) {
String name=user.getFullName();
String url=baseUrl
+"name="+URLEncoder.encode(name, "UTF-8")
+"&timestamp="+timestamp; Developer wants to check
return url;
}
whether timestamp is added
to the URL when this method
public String getUrl(User user) { is used
Date date=new Date();
Long time= date.getTime()/1000; //convert ms to seconds
String timestamp=time.toString();
return getUrl(user, timestamp);
}
}

Mock'em All!
Public class Util {

public String getUrl(User user, String timestamp) {
String name=user.getFullName();
String url=baseUrl
+"name="+URLEncoder.encode(name, "UTF-8")
+"&timestamp="+timestamp;
return url;
}

public String getUrl(User user) {
Date date=new Date();
Long time= date.getTime()/1000; //convert ms to seconds
String timestamp=time.toString();
return getUrl(user, timestamp);
} @Test
} public void shouldUseTimestampMethod() {
//given
Util util = new Util();
Util spyUtil = spy(util);

//when
spyUtil.getUrl(user);

//then
verify(spyUtil).getUrl(eq(user), anyString());
}

Dependency injection
Use the front door will save us

@Test
public void shouldAddTimestampToGeneratedUrl() {
//given
TimeProvider timeProvider = mock(TimeProvider.class);
Util util = new Util(timeProvider);
when(timeProvider.getTime()).thenReturn("12345");
util.set(timeProvider);

//when
String url = util.getUrl(user);

//then
assertThat(url).contains("timestamp=12345");
}

Single Responsibility Principle

A test should have one and only one reason to fail.

Testing two things at once
@DataProvider
public Object[][] data() {
return new Object[][] { {"48", true}, {"+48", true},
{"++48", true}, {"+48503", true}, {"+4", false},
{"++4", false}, {"", false},
{null, false}, {" ", false}, };
}

@Test(dataProvider = "data")
public void testQueryVerification(String query, boolean expected) {
assertEquals(expected, FieldVerifier.isValidQuery(query));
}

Testing two things at once
@DataProvider
public Object[][] data() {
return new Object[][] { {"48", true}, {"+48", true},
{"++48", true}, {"+48503", true}, {"+4", false},
{"++4", false}, {"", false},
{null, false}, {" ", false}, };
}

@Test(dataProvider = "data")
public void testQueryVerification(String query, boolean expected) {
assertEquals(expected, FieldVerifier.isValidQuery(query));
}

testQueryVerification1() {
assertEquals(true, FieldVerifier.isValidQuery(„48”));
}
assertEquals(true, FieldVerifier.isValidQuery(„+48”));
}
assertEquals(true, FieldVerifier.isValidQuery(„++48”));
}
assertEquals(true, FieldVerifier.isValidQuery(„+48503”));
}
...

Concentrate on one feature
@DataProvider
public Object[][] validQueries() {
return new Object[][] { {"48"}, {"48123"},
{"+48"}, {"++48"}, {"+48503"}};
}

@Test(dataProvider = "validQueries")
public void shouldRecognizeValidQueries(String validQuery) {
assertTrue(FieldVerifier.isValidQuery(validQuery));
}

@DataProvider
public Object[][] invalidQueries() {
return new Object[][] {
{"+4"}, {"++4"}, {""}, {null}, {" "} };
}

@Test(dataProvider = "invalidQueries")
public void shouldRejectInvalidQueries(String invalidQuery) {
assertFalse(FieldVerifier.isValidQuery(invalidQuery));
}

“And”
@Test
public void shouldReturnRedirectViewAndSendEmail() {
//given
given(bindingResult.hasErrors()).willReturn(false);
given(userData.toEntity()).willReturn(user);
given(userService.saveNewUser(eq(userData.toEntity())))
.willReturn(user);

//when
ModelAndView userRegisterResult = userRegisterController
.registerUser(userData, bindingResult, request);

//then
assertThat(userRegisterResult.getViewName())
.isEqualTo("redirect:/signin");
verify(mailSender).sendRegistrationInfo(user);
}

One feature at a time

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

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

Hint: forget about methods

Who the heck is “user_2” ?

@DataProvider
public static Object[][] usersPermissions() {
return new Object[][]{
{"user_1", Permission.READ},
{"user_1", Permission.WRITE},
{"user_1", Permission.REMOVE},
{"user_2", Permission.WRITE},
{"user_2", Permission.READ},
{"user_3", Permission.READ}
};
}

Ah, logged user can read and write...

@DataProvider
public static Object[][] usersPermissions() {
return new Object[][]{
{ADMIN, Permission.READ},
{ADMIN, Permission.WRITE},
{ADMIN, Permission.REMOVE},
{LOGGED, Permission.WRITE},
{LOGGED, Permission.READ},
{GUEST, Permission.READ}
};
}

domain1, domain2, domain3, ...

Do not make me learn the API!

server = new MockServer(responseMap, true,
new URL(SERVER_ROOT).getPort(), false);



private static final boolean RESPONSE_IS_A_FILE = true;
private static final boolean NO_SSL = false;

server = new MockServer(responseMap, RESPONSE_IS_A_FILE,
new URL(SERVER_ROOT).getPort(), NO_SSL);



server = new MockServerBuilder()
.withResponse(responseMap)
.withResponseType(FILE)
.withUrl(SERVER_ROOT)
.withoutSsl().create();

server = MockServerBuilder
.createNoSSLFileServer(responseMap, SERVER_ROOT);

Test methods names are important

• When test fails
• Relation to focused tests


@Test
public void testOperation() {
configureRequest("/validate")
rc = new RequestContext(parser, request)
assert rc.getConnector() == null
assert rc.getOperation().equals("validate")
}

“should” is better than “test”

• testOperation()
• testQuery()
• testConstructor()
• testFindUsersWithFilter()

• shouldRejectInvalidRequests()
• shouldSaveNewUserToDatabase()
• constructorShouldFailWithNegativePrice()
• shouldReturnOnlyUsersWithGivenName()

“should” is better than “test”

• Starting test method names
with “should” steers you in
the right direction.
http://jochopra.blogspot.com/

• “test” prefix makes your test
method a limitless bag
where you throw everything
worth testing

http://www.greenerideal.com/

@Test
public void testQuery(){
when(q.getResultList()).thenReturn(null);
assertNull(dao.findByQuery(Transaction.class, q, false));
assertNull(dao.findByQuery(Operator.class, q, false));
assertNull(dao.findByQuery(null, null, false));

List result = new LinkedList();
when(q.getResultList()).thenReturn(result);
assertEquals(dao.findByQuery(Transaction.class, q, false), result);
assertEquals(dao.findByQuery(Operator.class, q, false), result);
assertEquals(dao.findByQuery(null, null, false), null);

when(q.getSingleResult()).thenReturn(null);
assertEquals(dao.findByQuery(Transaction.class, q, true).size(), 0);
assertEquals(dao.findByQuery(Operator.class, q, true).size(), 0);
assertEquals(dao.findByQuery(null, null, true), null);

when(q.getSingleResult()).thenReturn(t);
assertSame(dao.findByQuery(Transaction.class, q, true).get(0), t);
when(q.getSingleResult()).thenReturn(o);
assertSame(dao.findByQuery(Operator.class, q, true).get(0), o);
assertSame(dao.findByQuery(null, null, true), null);
}

@Test
public void shouldReturnNullListWhenDaoReturnsNull {
when(q.getResultList()).thenReturn(null);
assertNull(dao.findByQuery(Transaction.class, q, false));
assertNull(dao.findByQuery(Operator.class, q, false));
assertNull(dao.findByQuery(null, null, false));
}
public void shouldReturnEmptyListWhenDaoReturnsIt {
List result = new LinkedList();
when(q.getResultList()).thenReturn(result);
assertEquals(dao.findByQuery(Transaction.class, q, false), result);
assertEquals(dao.findByQuery(Operator.class, q, false), result);
assertEquals(dao.findByQuery(null, null, false), null);
}
public void shouldReturnNullSingleResultWhenDaoReturnsNull {
assertEquals(dao.findByQuery(Transaction.class, q, true).size(), 0);
assertEquals(dao.findByQuery(Operator.class, q, true).size(), 0);
assertEquals(dao.findByQuery(null, null, true), null);
}
public void shouldReturnSingleResultReturnedByDao {
when(q.getSingleResult()).thenReturn(t);
assertSame(dao.findByQuery(Transaction.class, q, true).get(0), t);
when(q.getSingleResult()).thenReturn(o);
assertSame(dao.findByQuery(Operator.class, q, true).get(0), o);
assertSame(dao.findByQuery(null, null, true), null);
}

Assertion part is freaking huge
public void shouldPreDeployApplication() {
// given
Artifact artifact = mock(Artifact.class);
when(artifact.getFileName()).thenReturn("war-artifact-2.0.war");
ServerConfiguration config
= new ServerConfiguration(ADDRESS, USER, KEY_FILE, TOMCAT_PATH, TEMP_PATH);
Tomcat tomcat = new Tomcat(HTTP_TOMCAT_URL, config);
String destDir = new File(".").getCanonicalPath() + SLASH + "target" + SLASH;
new File(destDir).mkdirs();

// when
tomcat.preDeploy(artifact, new FakeWar(WAR_FILE_LENGTH));

//then
JSch jsch = new JSch();
jsch.addIdentity(KEY_FILE);
Session session = jsch.getSession(USER, ADDRESS, 22);
session.setConfig("StrictHostKeyChecking", "no");
session.connect();

Channel channel = session.openChannel("sftp");
session.setServerAliveInterval(92000);
channel.connect();
ChannelSftp sftpChannel = (ChannelSftp) channel;

sftpChannel.get(TEMP_PATH + SLASH + artifact.getFileName(), destDir);
sftpChannel.exit();

session.disconnect();

File downloadedFile = new File(destDir, artifact.getFileName());

assertThat(downloadedFile).exists().hasSize(WAR_FILE_LENGTH);
}

Just say it
public void shouldPreDeployApplication() {
// given
Artifact artifact = mock(Artifact.class);
when(artifact.getFileName())
.thenReturn(ARTIFACT_FILE_NAME);
ServerConfiguration config
= new ServerConfiguration(ADDRESS, USER,
KEY_FILE, TOMCAT_PATH, TEMP_PATH);
Tomcat tomcat = new Tomcat(HTTP_TOMCAT_URL, config);

// when
tomcat.preDeploy(artifact, new FakeWar(WAR_FILE_LENGTH));

// then
SSHServerAssert.assertThat(ARTIFACT_FILE_NAME)
.existsOnServer(tomcat).hasSize(WAR_FILE_LENGTH);
}

Asserting using private methods
@Test
public void testChargeInRetryingState() throws Exception {
// given
TxDTO request = createTxDTO(RequestType.CHARGE);
AndroidTransaction androidTransaction = ...

// when
final TxDTO txDTO = processor.processRequest(request);

// then
List<AndroidTransactionStep> steps
= new ArrayList<>(androidTransaction.getSteps());
AndroidTransactionStep lastStep = steps.get(steps.size() - 1);
assertEquals(lastStep.getTransactionState(), CHARGED_PENDING);
assertEquals(txDTO.getResultCode(), CHARGED);

}

Asserting using private methods
@Test
// given
TxDTO request = createTxDTO(RequestType.CHARGE);

// when

// then
assertState(request, androidTransaction,
CHARGED, CHARGE_PENDING, AS_ANDROID_TX_STATE,
ClientMessage.SUCCESS, ResultCode.SUCCESS);
}

Matchers vs. private methods
assertState(TxDTO txDTO, AndroidTransaction androidTransaction,
AndroidTransactionState expectedAndroidState,
AndroidTransactionState expectedPreviousAndroidState,
ExtendedState expectedState,
String expectedClientStatus, ResultCode expectedRequestResultCode) {
final List<AndroidTransactionStep> steps
= new ArrayList<>(androidTransaction.getTransactionSteps());
final boolean checkPreviousStep = expectedAndroidState != null;
assertTrue(steps.size() >= (checkPreviousStep ? 3 : 2));

if (checkPreviousStep) {
AndroidTransactionStep lastStep = steps.get(steps.size() - 2);
assertEquals(lastStep.getTransactionState(),
expectedPreviousAndroidState);
}

final AndroidTransactionStep lastStep = steps.get(steps.size() - 1);
assertEquals(lastStep.getTransactionState(), expectedAndroidState);
assertEquals(lastStep.getMessage(), expectedClientStatus);

assertEquals(txDTO.getResultCode(), expectedRequestResultCode);
assertEquals(androidTransaction.getState(), expectedAndroidState);
assertEquals(androidTransaction.getExtendedState(), expectedState);

if (expectedClientStatus == null) {
verifyZeroInteractions(client);
}
}

Matchers vs. private methods

@Test
// given
TxDTO request = createTxDTO(CHARGE);
// when
// then
assertThat(androidTransaction).hasState(CHARGED)
.hasMessage(ClientMessage.SUCCESS)
.hasPreviousState(CHARGE_PENDING)
.hasExtendedState(null);
assertEquals(txDTO.getResultCode(), ResultCode.SUCCESS);
}

Asserting implementation details

public void invalidTxShouldBeCanceled() {
...
String fileContent =
FileUtils.getContentOfFile("response.csv");
assertTrue(fileContent.contains(
"CANCEL,123,123cancel,billing_id_123_cancel,SUCCESS,"));
}

Asserting implementation details

...
assertTrue(fileContent.contains(
"CANCEL,123,123cancel,billing_id_123_cancel,SUCCESS,"));
}

...
TxDTOAssert.assertThat(fileContent)
.hasTransaction("123cancel").withResultCode(SUCCESS);
}

Know your tools
• Unit testing framework • Additional libraries
• Use of temporary file rule
• Hamcrest, FEST, Mockito,
• Listeners catch-exception, awaitility, …
• Concurrency • Build tool
• @Before/@After • Parallel execution

• Parametrized tests • CI

• Test dependencies • IDE
• Templates
• Shortcuts

Expected exceptions
@Test(expected=IndexOutOfBoundsException.class)
public void shouldThrowExceptionGettingElementOutsideTheList() {
MyList<Integer> list = new MyList<Integer>();
list.add(0);
list.add(1);
list.get(2);
}

Expected exceptions
@Test(expected=IndexOutOfBoundsException.class)
public void shouldThrowExceptionGettingElementOutsideTheList() {
list.add(0);
list.add(1);
list.get(2);
} http://code.google.com/p/catch-exception/

@Test
public void shouldThrowExceptionGettingtElementOutsideTheList()
list.add(0);
list.add(1);
catchException(list).get(2);
assertThat(caughtException())
.isExactlyInstanceOf(IndexOutOfBoundsException.c
}

Expected exceptions (with catch-exception)

@Test
public void shouldThrowException() throws SmsException {

catchException(gutExtractor)
.extractGut(„invalid gut”);

then(caughtException())
.isInstanceOf(SmsException.class)
.hasMessage("Invalid gut")
.hasNoCause();
}

http://code.google.com/p/catch-exception/

Awaitility

@Test
public void updatesCustomerStatus() throws Exception {

// Publish an asynchronous event:
publishEvent(updateCustomerStatusEvent);

// Awaitility lets you wait until
// the asynchronous operation completes:
await().atMost(5, SECONDS)
.until(costumerStatusIsUpdated());
...
}

http://code.google.com/p/awaitility/

What do you really want to test?

@Test
public void shouldAddAUser() {
User user = new User();
userService.save(user);
assertEquals(dao.getNbOfUsers(), 1);
}

You wanted to see that the number increased

@Test
public void shouldAddAUser() {
int nb = dao.getNbOfUsers();
User user = new User();
userService.save(user);
assertEquals(dao.getNbOfUsers(), nb + 1);
}

Because:
1) This is closer to what you wanted to test
2) There is no assumption about the database “users” table being empty

The dream of stronger, random-powered tests
public void myTest() {
SomeObject obj = new SomeObject(
randomName(), randomValue(), ....);
// testing of obj here
}

Does it make your test stronger?

The dream of stronger, random-powered tests
randomName(), randomValue(), ....);
}

Does it make your test stronger?
...or does it only bring confusion?
Test failed
Expected
SomeObject(„a”, „b”, ....)
but got
SomeObject(„*&O*$NdlF”, „#idSLNF”, ....)

Random done wrong
a, b, c, productCode());
}

private String productCode(){
String[] codes = {"Code A", "Code B",
"Code C", "Code D"};
int index = rand.nextInt(codes.length);
return codes[index];
}

Asking for troubles...
LoggingPropertyConfigurator configurator = mock(...);
BaseServletContextListener baseServletContextListener =
= new BaseServletContextListener(configurator)

@Test public void shouldLoadConfigProperties() { Should load some
baseServletContextListener.contextInitialized();default config
verify(configurator).configure(any(Properties.class));
}

@Test(expected = LoggingInitialisationException.class)
Should load this
public void shouldThrowExceptionIfCantLoadConfiguration() {
specific file
System.setProperty("logConfig", "nonExistingFile");
baseServletContextListener.contextInitialized();
}

Asking for troubles...
LoggingPropertyConfigurator configurator = mock(...);
BaseServletContextListener baseServletContextListener =
= new BaseServletContextListener(configurator)

@Test public void shouldLoadConfigProperties() {
verify(configurator).configure(any(Properties.class));
}

@Test(expected = LoggingInitialisationException.class)
public void shouldThrowExceptionIfCantLoadConfiguration() {
System.setProperty("logConfig", "nonExistingFile");
}

@Before
public void cleanSystemProperties() {
...
}

Test-last? No!

• makes people not write tests at all
• makes people do only happy path testing
• tests reflect the implementation

Always TDD?

For six or eight hours spread over the next few weeks I
struggled to get the first test written and running.
Writing tests for Eclipse plug-ins is not trivial, so it’s not
surprising I had some trouble. [...] In six or eight hours
of solid programming time, I can still make significant
progress. If I’d just written some stuff and verified it by
hand, I would probably have the final answer to whether
my idea is actually worth money by now. Instead, all I
have is a complicated test that doesn’t work, a pile
of frustration, eight fewer hours in my life, and the
motivation to write another essay.
Kent Beck, Just Ship, Baby

There is so much more to discuss…
• Integration / end-to-end tests which are not parametrized
(so they all try to set up jetty on port 8080),
• Tests which should be really unit, but use Spring context
to create objects,
• Tests with a lot of dependencies between them (a
nightmare to maintain!),
• Tests which are overspecified and will fail whenever you
touch the production code,
• Tests with monstrous objects-creation code,
• Tests which run slow,
• Tests which try to cover the deficiencies of production
code and end up being a total mess,
• Tests which verify methods instead of verifying
responsibilities of a class,
• Happy path tests,
• etc., etc.

Treat tests as the first class citizens
• do it everyday or forget about it • make tests readable using matchers,
• use the right tool for the job builders and good names
• and learn to use it! • test behaviour not methods
• do not live with broken windows • be pragmatic about the tests you write
• respect KISS, SRP, DRY (?) • TDD always?
• write good code, and you will also write • what is the best way to test it?
good tests unit/integration/end-to-end ?
• or rather write good tests and you • automate!
will get good code for free • always concentrate on what is worth
• code review your tests testing
• do more than happy path testing • ask yourself questions like: 'is it
really important that X should send
• do not make the reader learn the API,
message Y to Z?'
make it obvious
• use the front door – state testing before
• bad names lead to bad tests
interaction testing (mocks)

Thank you!
You can learn more about writing
high quality tests by reading my
book – „Practical Unit Testing
with TestNG and Mockito”.

You can also participate in
writing of my
new (free!) e-book devoted to
bad and good tests.

Tests Good Bad

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