a mock to far - geecon
TRANSCRIPT
One mock too far
@milipski
Pragmatists.pl
public class InvoiceService {
private InvoiceDataFactory invoiceDataFactory; private InvoiceRepository invoiceRepository;
public Invoices findAll() {
InvoiceData invoiceData = invoiceDataFactory.create(); Invoices invoices = invoiceRepository.findAll(invoiceData);
return invoices; }}
@Testpublic void should_fetch_from_repository_using_invoice_data_from_factory() {
InvoiceDataFactory invoiceDataFactory = mock(InvoiceDataFactory.class); InvoiceData invoiceData = new InvoiceData(); when(invoiceDataFactory.create()).thenReturn(invoiceData); InvoiceRepository invoiceRepository = mock(InvoiceRepository.class); InvoiceService invoiceService = new InvoiceService(invoiceDataFactory, invoiceRepository);
invoiceService.findAll();
verify(invoiceDataFactory).create(); verify(invoiceRepository).findAll(invoiceData);}
@Testpublic void should_fetch_from_repository_using_invoice_data_from_factory() {
InvoiceDataFactory invoiceDataFactory = mock(InvoiceDataFactory.class); InvoiceData invoiceData = new InvoiceData(); when(invoiceDataFactory.create()).thenReturn(invoiceData); InvoiceRepository invoiceRepository = mock(InvoiceRepository.class); InvoiceService invoiceService = new InvoiceService(invoiceDataFactory, invoiceRepository);
invoiceService.findAll();
verify(invoiceDataFactory).create(); verify(invoiceRepository).findAll(invoiceData);}
@Testpublic void should_fetch_from_repository_using_invoice_data_from_factory() {
InvoiceDataFactory invoiceDataFactory = mock(InvoiceDataFactory.class); InvoiceData invoiceData = new InvoiceData(); when(invoiceDataFactory.create()).thenReturn(invoiceData); InvoiceRepository invoiceRepository = mock(InvoiceRepository.class); InvoiceService invoiceService = new InvoiceService(invoiceDataFactory, invoiceRepository);
invoiceService.findAll();
verify(invoiceDataFactory).create(); verify(invoiceRepository).findAll(invoiceData);}
@Testpublic void should_fetch_from_repository_using_invoice_data_from_factory() {
InvoiceDataFactory invoiceDataFactory = mock(InvoiceDataFactory.class); InvoiceData invoiceData = new InvoiceData(); when(invoiceDataFactory.create()).thenReturn(invoiceData); InvoiceRepository invoiceRepository = mock(InvoiceRepository.class); InvoiceService invoiceService = new InvoiceService(invoiceDataFactory, invoiceRepository);
invoiceService.findAll();
verify(invoiceDataFactory).create(); verify(invoiceRepository).findAll(invoiceData);}
duplication of implementation
InvoiceData invoiceData = invoiceDataFactory.create();
Invoices invoices = invoiceRepository.findAll(invoiceData);
when(invoiceDataFactory .create()).thenReturn(invoiceData);
verify(invoiceRepository).findAll(invoiceData);
Bad readability
@Testpublic void should_fetch_from_repository_using_invoice_data_from_factory() { InvoiceDataFactory invoiceDataFactory=mock(InvoiceDataFactory.class); InvoiceData invoiceData = new InvoiceData(); when(invoiceDataFactory.create()).thenReturn(invoiceData); InvoiceRepository invoiceRepository = mock(InvoiceRepository.class); InvoiceService invoiceService = new InvoiceService( invoiceDataFactory, invoiceRepository);
invoiceService.findAll();
verify(invoiceDataFactory).create(); verify(invoiceRepository).findAll(invoiceData);}
Change-Detector tests
fail after ANY change to production code.
Mock Objects are not bad
but we use them in a bad way
“Procedural code gets information
then makes decisions ...”
Alec Sharp
public class InvoiceService {
private InvoiceDataFactory invoiceDataFactory; private InvoiceRepository invoiceRepository;
public Invoices findAll() {
InvoiceData invoiceData = invoiceDataFactory.create(); Invoices invoices = invoiceRepository.findAll(invoiceData);
return invoices; }}
Mocks don't get along with
procedural code
QUERY COMMAND
INCOMMING
OUTGOING
Incoming Query
query()
Incoming Query
query()
response
public class InvoiceService {
private InvoiceDataFactory invoiceDataFactory; private InvoiceRepository invoiceRepository;
public Invoices findAll() {
InvoiceData invoiceData = invoiceDataFactory.create(); Invoices invoices = invoiceRepository.findAll(invoiceData);
return invoices; }}
Incoming Query
Stubs instead of mocks
@Testpublic void should_fetch_invoices() { InvoiceService invoiceService = new InvoiceService( new InvoiceDataFactoryStub(), new InvoiceRepositoryStub( new Invoice("123"), new Invoice("456")));
Invoices invoices = invoiceService.findAll();
assertThat(invoices).containsOnly(new Invoice("123"), new Invoice("456"));}
Asserting on retuned value
@Testpublic void should_fetch_invoices() { InvoiceService invoiceService = new InvoiceService( new InvoiceDataFactoryStub(), new InvoiceRepositoryStub( new Invoice("123"), new Invoice("456")));
Invoices invoices = invoiceService.findAll();
assertThat(invoices).containsOnly(new Invoice("123"), new Invoice("456"));}
Mocks assert on messages
Stubs return values
QUERY COMMAND
INCOMMING Assert on result
OUTGOING
Outgoing Query
query()
Outgoing Query
query()
response
Outgoing Query
public class InvoiceService {
private InvoiceDataFactory invoiceDataFactory; private InvoiceRepository invoiceRepository;
public Invoices findAll() {
InvoiceData invoiceData = invoiceDataFactory.create(); Invoices invoices = invoiceRepository.findAll(invoiceData);
return invoices; }}
QUERY COMMAND
INCOMMING Assert on result
OUTGOING Stub, avoid asserting
Don't mess mocks with stubs
Incoming Command
command()
Incoming Command
command()
PrepaidTopup service example
press(key)
sendRequest()
getSelection() PrepaidTopup
PrepaidTopup service example
press(key)
sendRequest()
getSelection() PrepaidTopup
Incoming Command
@Testpublic void makes_selection_by_pressing_numbers() { PrepaidTopup prepaidTopup = new PrepaidTopupStand(new OrderHandler()); prepaidTopup.press(5); prepaidTopup.press(0);
String selection = prepaidTopup.getSelection(); assertThat(selection).isEqualTo("50");}
QUERY COMMAND
INCOMMING Assert on result Assert on state change
OUTGOING Stub, avoid asserting
Outgoing Command
command()
“Procedural code gets information
then makes decisions,
Object Oriented code tells objects to do things”
Alec Sharp
In OOP behaviour is found in messages
PrepaidTopup service
press(key)
sendRequest()
PrepaidTopup placeOrder(selection) OrderHandler
public interface PrepaidTopup {
public void press(Integer number);
public void sendRequest();
}
PrepaidTopup service
@Testpublic void sends_request_with_selection() { OrderHandler orderHandler = mock(OrderHandler.class); PrepaidTopup prepaidTopup = new PrepaidTopupStand(orderHandler);
prepaidTopup.press(5); prepaidTopup.press(0); prepaidTopup.sendRequest();
verify(orderHandler).placeOrder("50");}
Verify on Outgoing Message
@Testpublic void order_is_placed_after_request_with_selection() { //OrderHandler orderHandler = mock(OrderHandler.class); OrderHandler orderHandler = new OrderExecutor(); PrepaidTopup prepaidTopup = new PrepaidTopupStand(orderHandler);
prepaidTopup.press(5); prepaidTopup.press(0); prepaidTopup.sendRequest();
//verify(orderHandler).placeOrder("50"); assertThat(orderHandler.getOrders()).contains("50");}
Asserting on side effect
Asserting on side effect
press(key)
sendRequest()
PrepaidTopup placeOrder(selection) OrderExecutor
+10%
@Testpublic void order_is_placed_after_request_with_selection() { OrderHandler orderHandler = new OrderExecutor(); PrepaidTopup prepaidTopup = new PrepaidTopupStand(orderHandler);
prepaidTopup.press(5); prepaidTopup.press(0); prepaidTopup.sendRequest();
assertThat(orderHandler.getOrders()).contains("50"); //java.lang.AssertionError expecting <"55"> to contain: <"50">}
Asserting on side effect
QUERY COMMAND
INCOMMING Assert on result Assert on state change
OUTGOING Stub, avoid asserting Assert on Mocks
Thank You!