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2013 DevFest Vienna - Bad Tests, Good Tests
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2013 DevFest Vienna - Bad Tests, Good Tests

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my talk from 2013 DevFest Vienna about how to write really good tests. I hope you enjoy it!

my talk from 2013 DevFest Vienna about how to write really good tests. I hope you enjoy it!

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    2013 DevFest Vienna - Bad Tests, Good Tests 2013 DevFest Vienna - Bad Tests, Good Tests Presentation Transcript

    • 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 • Trainer • Interested? Contact me! • kaczanowski.tomek@gmail.com • Trainings in Vienna? Sure!
    • 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 ;)
    • Who writes tests?
    • What about the ROI?
    • http://ripper1331.deviantart.com
    • http://ripper1331.deviantart.com
    • http://ripper1331.deviantart.com Survey is show junior devops are still believe in Tooth Fairy, Santa Claus and documentation http://twitter.com/#!/devops_borat
    • http://ripper1331.deviantart.com Survey is show junior devops are still believe in Tooth Fairy, Santa Claus and documentation http://twitter.com/#!/devops_borat If you think good design is expensive, you should look at the cost of bad design. Dr Ralph Speth, CEO Jaguar
    • 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 the right test write this test right
    • Ancient times
    • 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
    • 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(); } } 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");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(); } } 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
    • 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 • Manual verification is evil • Do not live with broken window • If you don't fix things no one else will! • It is a full time job! • You should be informed why your test failed • Master your tools • …at least learn the basics!
    • Mocks & Co.
    • @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"); }
    • Mock'em All! ModelAndView from SpringMVC – a mere container for data, without any behaviour @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"); }
    • Do not test interactions if not needed @Test public void shouldAddTimeZoneToModelAndView() { //given UserFacade userFacade = mock(UserFacade.class); ModelAndView modelAndView = new ModelAndView(); given(userFacade.getTimezone()).willReturn("timezone X"); //when new UserDataInterceptor(userFacade) .postHandle(null, null, null, modelAndView); //then a pseudocode but that is what we mean assertThat(modelAndView).contains("timezone", "timezone X"); }
    • 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 is used 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); } }
    • public class Util { Developer public String getUrl(User user, String timestamp) { wants to check ... whether timestamp is added to } the URL when this method is public String getUrl(User user) { ... } } used
    • Bad design → bad tests public class Util { Developer public String getUrl(User user, String timestamp) { wants to check ... whether timestamp is added to } the URL when this method is public String getUrl(User user) { ... } used } @Test public void shouldUseTimestampMethod() { //given Util util = new Util(); Util spyUtil = Mockito.spy(util); //when spyUtil.getUrl(user); //then verify(spyUtil).getUrl(eq(user), anyString()); }
    • Dependency Injection will save us @Test public void shouldGenerateURLWithTimestamp() { //given TimeProvider timeProvider = mock(TimeProvider.class); Util util = new Util(timeProvider); given(timeProvider.getTime()).willReturn("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, } testQueryVerification2() { assertEquals(true, } testQueryVerification3() { assertEquals(true, } testQueryVerification4() { assertEquals(true, } ... FieldVerifier.isValidQuery(„48”)); FieldVerifier.isValidQuery(„+48”)); FieldVerifier.isValidQuery(„++48”)); FieldVerifier.isValidQuery(„+48503”));
    • 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)); }
    • 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
    • Readability is the king variables
    • @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} }; }
    • 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} }; } Who the heck is “user_2”?!
    • 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, ...
    • domain1, domain2, domain3, ...
    • domain1, domain2, domain3, ...
    • Do not make me learn the API! server = new MockServer(responseMap, true, new URL(SERVER_ROOT).getPort(), false);
    • 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);
    • Do not make me learn the API! server = new MockServer(responseMap, true, new URL(SERVER_ROOT).getPort(), false); server = createFileNonSSLMockServer(responseMap);
    • Do not make me learn the API! server = new MockServer(responseMap, true, new URL(SERVER_ROOT).getPort(), false); server = new MockServerBuilder() .withResponse(responseMap) .withResponseType(FILE) .withUrl(SERVER_ROOT) .withoutSsl().create(); server = MockServerBuilder .createFileNoSSLServer(responseMap, SERVER_ROOT);
    • Readability is the king test method names
    • Test methods names are important • When test fails • Relation to focused tests
    • What is it all about? @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 methods names are important @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); when(q.getSingleResult()).thenReturn(null); assertSame(dao.findByQuery(null, null, true), null);
    • Test methods names are important @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 { 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); } 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); when(q.getSingleResult()).thenReturn(null); assertSame(dao.findByQuery(null, null, true), null); }
    • Assertions
    • 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); }
    • 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); WHY NOT CREATE A PRIVATE ASSERTION METHOD? // when WHY NOT USE tomcat.preDeploy(artifact, new FakeWar(WAR_FILE_LENGTH)); // then assertThatFileIsOnServer(ARTIFACT_FILE_NAME, Tomcat, WAR_FILE_LENGTH); }
    • Assertions repeated in many tests @Test public void testChargeInRetryingState() throws Exception { // given TxDTO request = createTxDTO(RequestType.CHARGE); AndroidTransaction androidTransaction = ... request.setTransaction(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); }
    • Assertions repeated in many tests @Test public void testChargeInRetryingState() throws Exception { // given TxDTO request = createTxDTO(RequestType.CHARGE); AndroidTransaction androidTransaction = ... request.setTransaction(androidTransaction); WHY NOT CREATE A PRIVATE ASSERTION METHOD? // 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 public void testChargeInRetryingState() throws Exception { // given TxDTO request = createTxDTO(RequestType.CHARGE); AndroidTransaction androidTransaction = ... // when final TxDTO txDTO = processor.processRequest(request); // then assertState(request, androidTransaction, CHARGED, CHARGE_PENDING, AS_ANDROID_TX_STATE, ClientMessage.SUCCESS, ResultCode.SUCCESS); }
    • 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); } }
    • Custom assertions to the rescue @Test public void testChargeInRetryingState() throws Exception { // given TxDTO request = createTxDTO(CHARGE); AndroidTransaction androidTransaction = ... // when final TxDTO txDTO = processor.processRequest(request); // 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 public void invalidTxShouldBeCanceled() { ... String fileContent = FileUtils.getContentOfFile("response.csv"); assertTrue(fileContent.contains( "CANCEL,123,123cancel,billing_id_123_cancel,SUCCESS,")); } public void invalidTxShouldBeCanceled() { ... String fileContent = FileUtils.getContentOfFile("response.csv"); TxDTOAssert.assertThat(fileContent) .hasTransaction("123cancel").withResultCode(SUCCESS); }
    • Know your tools • Unit testing framework • Use of temporary file rule • Additional libraries • Hamcrest, FEST, Mockito, catch-exception, awaitility, JUnitParams, tempus-fugit, … • Listeners • Concurrency • @Before/@After • Parametrized tests • Test dependencies • Build tool • Parallel execution • CI • 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() { MyList<Integer> list = new MyList<Integer>(); list.add(0); list.add(1); list.get(2); } http://code.google.com/p/catch-exception/ @Test public void shouldThrowExceptionGettingtElementOutsideTheList() { MyList<Integer> list = new MyList<Integer>(); list.add(0); list.add(1); catchException(list).get(2); assertThat(caughtException()) .isExactlyInstanceOf(IndexOutOfBoundsException.cla }
    • 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
    • Asking for troubles... LoggingPropertyConfigurator configurator = mock(...); BaseServletContextListener baseServletContextListener = = new BaseServletContextListener(configurator) @Test public void shouldLoadConfigProperties() { Should load some default config baseServletContextListener.contextInitialized(); verify(configurator).configure(any(Properties.class)); } Should load this specific file @Test(expected = LoggingInitialisationException.class) public void shouldThrowExceptionIfCantLoadConfiguration() { System.setProperty("logConfig", "nonExistingFile"); baseServletContextListener.contextInitialized(); }
    • Asking for troubles... LoggingPropertyConfigurator configurator = mock(...); BaseServletContextListener baseServletContextListener = = new BaseServletContextListener(configurator) @Test public void shouldLoadConfigProperties() { baseServletContextListener.contextInitialized(); verify(configurator).configure(any(Properties.class)); } @Test(expected = LoggingInitialisationException.class) public void shouldThrowExceptionIfCantLoadConfiguration() { System.setProperty("logConfig", "nonExistingFile"); baseServletContextListener.contextInitialized(); } @Before public void cleanSystemProperties() { ... }
    • Ceremony @Test public void shouldBeAdministrator() { //given User user = new Administrator(); //when boolean administrator = user.isAdministrator(); boolean advertiser = user.isAdvertiser(); boolean domainer = user.isDomainer(); //then assertThat(administrator).isTrue(); assertThat(advertiser).isFalse(); assertThat(domainer).isFalse(); }
    • Ceremony @Test public void shouldBeAdministrator() { User user = new Administrator(); assertThat(user.isAdministrator()).isTrue(); assertThat(user.isAdvertiser()).isFalse(); assertThat(user.isDomainer()).isFalse(); }
    • private static final int PER_PAGE = 10; @Test public void shouldGiveOffsetZeroWhenOnZeroPage() { Pager pager = new Pager(PER_PAGE); assertThat(pager.getOffset()).isEqualTo(0); } @Test public void shouldIncreaseOffsetWhenGoingToPageOne() { Pager pager = new Pager(PER_PAGE); pager.goToNextPage(); assertThat(pager.getOffset()).isEqualTo(PER_PAGE); }
    • private static final int PER_PAGE = 10; @Test public void shouldGiveOffsetZeroWhenOnZeroPage() { Pager pager = new Pager(PER_PAGE); assertThat(pager.getOffset()).isEqualTo(0); } @Test public void shouldIncreaseOffsetWhenGoingToPageOne() { Pager pager = new Pager(PER_PAGE); pager.goToNextPage(); assertThat(pager.getOffset()).isEqualTo(PER_PAGE); } public void goToNextPage() { this.offset = +perPage; }
    • Test-last? • makes people not write tests at all • makes people do only happy path testing • tests reflect the implementation
    • Treat tests as the first class citizens • do it everyday or forget about it • • use the right tool for the job • and learn to use it! make tests readable using matchers, builders and good names • test behaviour not methods • do not live with broken windows • • respect KISS, SRP, DRY (?) be pragmatic about the tests you write • TDD always? • write good code, and you will also write good tests • or rather write good tests and you will get good code for free • do not make the reader learn the API, make it obvious • bad names lead to bad tests automate! • always concentrate on what is worth testing • ask yourself questions like: 'is it really important that X should send message Y to Z?' • use the front door – state testing before interaction testing (mocks) do more than happy path testing • what is the best way to test it? unit/integration/end-to-end ? • code review your tests • •
    • Thank you! You can learn more about writing high quality tests by reading my book – „Practical Unit Testing”. You can also participate in writing of my new (free!) e-book devoted to bad and good tests.