Sustaining Test-Driven Development

Sustainable
Test-Driven
Development
Steve Freeman and Nat Pryce

www.growing-object-oriented-software.com 2011

Out Now

Friday, 9 September 2011

Why Sustainability
Matters (a)
public class ExchangeRateUploaderTest extends EasyMockTestCase {
private Logger logger;
private CurrencyManager mockCurrencyManager;
private ExchangeRateManager mockExchangeRateManager;
private PriceManagerFactory mockPriceManagerFactory;
private PriceManager mockPriceManager;
private GodObject mockGod;
private DatabaseFacade mockPersistenceManager;
private DatabaseFacade mockFrameworkPersistenceManager;
private CyclicProcessManager mockCyclicProcessManager;
private SystemVariableManager mockSystemVariableManager;
private ScreenManager mockScreenManager;
private Registry registry;
private User adminUser;
private Server server;

private ExchangeRateUploader newExchangeRateUploader(CyclicProcessThread thread) {
return new ExchangeRateUploader(thread) {
@Override protected void initializeAction() throws FrameworkException {
// Does nothing to prevent excessive mocking
}
@Override public Logger getLogger() { return logger; }
@Override protected void setLogMDC() { }
@Override protected User getUser() { return adminUser; }
@Override protected CurrencyManager newCurrencyManager() { return mockCurrencyManager; }
@Override protected PriceManagerFactory newPriceManagerFactory() { return mockPriceManagerFactory; }
@Override protected CyclicProcessManager newCyclicProcessManager() { return mockCyclicProcessManager; }
@Override protected DatabaseFacade newPersistenceManager() { return mockPersistenceManager; }
@Override protected Registry newTaskPerformanceRegistry() { return registry; }
@Override public PriceDataManager getPriceDataManager() { return null; }
@Override protected ExchangeRateManager newExchangeRateManager() { return mockExchangeRateManager; }
};

}


Why Sustainability
public void testInternalAction() throws FrameworkException {
mockGod = addMock(GodObject.class);
expect(mockGod.getPriceDataManager()).andStubReturn(null);
mockPersistenceManager = addMock(DatabaseFacade.class);
registry = addMock(Registry.class);
Matters (b)
adminUser = new TestUser("Admin", "", "", new TestCompany("company"), "");
mockCyclicProcessManager();

registry.finalizeThisThread(isA(String.class), isA(String.class));
Date now = DateUtils.trimMinutesAndSecondsFromDate(new Date());

mockSystemVariableManager();
mockLogger();
mockContextPersistenceManager();
mockPriceManager();

CyclicProcessThread thread = mockUserStateAndGetCyclicProcessThread();

String primeName = "prime";
String aName = "a";
String otherName = "other";

Currency primeCurrency = new TestCurrency(primeName, true);
Currency aCurrency = new TestCurrency(aName, true);
Currency otherCurrency = new TestCurrency(otherName, false);

FXCurrencyPair aCurrencyPair = new FXCurrencyPair(primeCurrency, aCurrency);
FXCurrencyPair otherCurrencyPair = new FXCurrencyPair(otherCurrency, primeCurrency);

setupCurrencyManager(primeCurrency, aCurrency, otherCurrency);
mockExchangeRateManager = addMock(ExchangeRateManager.class);

mockGetFXRatesAtDatesForCurrencies(now, aCurrencyPair, otherCurrencyPair);

FrameworkNumber aCurrencyValue = new FrameworkNumber("5");
FrameworkNumber otherCurrencyValue = new FrameworkNumber("2");
ExchangeRate aCurrencyRate = new ExchangeRate(primeCurrency, aCurrency, aCurrencyValue, now);
ExchangeRate otherCurrencyRate = new ExchangeRate(otherCurrency, primeCurrency, otherCurrencyValue, now);
expect(mockCurrencyManager.getParentToFractionalCurrencyMapForFractionalCurrency()).andStubReturn(newMap());

expect(
mockExchangeRateManager.saveExchangeRate(null, new FrameworkString(primeName), new FrameworkString(aName), aCurrencyValue,
new FrameworkDate(now))).andReturn(null);
expect(
mockExchangeRateManager.saveExchangeRate(null, new FrameworkString(otherName), new FrameworkString(primeName),
otherCurrencyValue, new FrameworkDate(now))).andReturn(null);

Map<String, ExchangeRate> out = new HashMap<String, ExchangeRate>();
out.put("primea", aCurrencyRate);
out.put("otherprime", otherCurrencyRate);
expect(mockPriceManager.getLatestExchangeRates(newList(aCurrencyPair, otherCurrencyPair))).andReturn(out);

mockPMFactoryCleanup();

replayMocks();

ExchangeRateUploader uploader = newExchangeRateUploader(thread);
uploader.initialise();
uploader.run();
}


Why Sustainability
private void mockPMFactoryCleanup() {
Matters (c)
PersistenceFactory mockPersistenceFactory = addMock(PersistenceFactory.class);
mockPersistenceFactory.purgeAllStateForThisThread();
expect(mockGod.getPersistenceFactory()).andReturn(mockPersistenceFactory).anyTimes();
expect(mockPersistenceFactory.getExceptionsInRequest()).andReturn(Collections.<Throwable>emptyList()).times(1);
}

private void mockCyclicProcessManager() throws CyclicProcessException {
mockCyclicProcessManager = addMock(CyclicProcessManager.class);
expect(mockGod.getCyclicProcessManager()).andStubReturn(mockCyclicProcessManager);
mockCyclicProcessManager.updateServerCyclicProcessCurrentRunStatus(isA(String.class),
isA(LISTENER_STATUS.class), isA(String.class), isA(Double.class), isA(Date.class));
expectLastCall().anyTimes();
server = addMock(Server.class);
expect(mockCyclicProcessManager.getThisServer()).andStubReturn(server);
}

private void setupCurrencyManager(Currency primeCurrency, Currency aCurrency, Currency otherCurrency) {
mockCurrencyManager = addMock(CurrencyManager.class);
List<Currency> allCurrencies = new ArrayList<Currency>();
allCurrencies.add(aCurrency);
allCurrencies.add(primeCurrency);
allCurrencies.add(otherCurrency);
expect(mockCurrencyManager.getPrimeCurrency()).andReturn(primeCurrency).anyTimes();
expect(mockCurrencyManager.getAllParentCurrencies()).andReturn(allCurrencies).times(2);
}

private void mockGetFXRatesAtDatesForCurrencies(Date now, FXCurrencyPair aCurrencyPair,
FXCurrencyPair otherCurrencyPair) throws CurrencyException
{
FrameworkNumber originalACurrencyRate = new FrameworkNumber("1.23");
Map<FXCurrencyPair, Collection<Date>> currencyPairAndDatesMap = new HashMap<FXCurrencyPair, Collection<Date>>();
currencyPairAndDatesMap.put(aCurrencyPair, Arrays.asList(now));
currencyPairAndDatesMap.put(otherCurrencyPair, Arrays.asList(now));
FXCurrencyPairRates outputObj = addMock(FXCurrencyPairRates.class);
expect(outputObj.rateMapSize()).andReturn(5).anyTimes();
expect(outputObj.getActualPriceDateForCurrencyPair(aCurrencyPair, now)).andReturn(null).once();
expect(outputObj.getRateFromFxRateMap(now, aCurrencyPair)).andReturn(originalACurrencyRate).once();
expect(outputObj.getActualPriceDateForCurrencyPair(otherCurrencyPair, now)).andReturn(null).once();
expect(outputObj.getRateFromFxRateMap(now, otherCurrencyPair)).andReturn(originalACurrencyRate);
expect(mockExchangeRateManager.getFXRatesAtDatesForCurrencies(currencyPairAndDatesMap)).andReturn(outputObj);
}


Why Sustainability
Role mockAdminRole = addMock(Role.class);
Matters (d)
private CyclicProcessThread mockUserStateAndGetCyclicProcessThread() {

CyclicProcessThread thread = addMock(CyclicProcessThread.class);
expect(thread.getAdminRole()).andReturn(mockAdminRole).anyTimes();
expect(thread.getAdminUser()).andReturn(adminUser).anyTimes();
thread.interrupt();
expectLastCall();
mockScreenManager = addMock(ScreenManager.class);
expect(mockGod.getScreenManager()).andReturn(mockScreenManager).anyTimes();
mockScreenManager.setThreadSignedOnState(new SignedOnState(adminUser, mockAdminRole, false));
expect(thread.getGod()).andReturn(mockGod).anyTimes();
expect(thread.getShutdownInProgress()).andReturn(false).anyTimes();
return thread;
}

private void mockContextPersistenceManager() {
mockFrameworkPersistenceManager = addMock(DatabaseFacade.class);
expect(mockGod.getDatabaseFacade()).andReturn(mockFrameworkPersistenceManager).anyTimes();
mockFrameworkPersistenceManager.beginNewSession();
}

private void mockPriceManager() throws PriceException {
mockPriceManagerFactory = addMock(PriceManagerFactory.class);
mockPriceManager = addMock(PriceManager.class);
expect(mockPriceManagerFactory.newPriceManager(mockFrameworkPersistenceManager,
mockSystemVariableManager, null))
.andReturn(mockPriceManager).once();
}

private void mockSystemVariableManager() {
mockSystemVariableManager = addMock(SystemVariableManager.class);
expect(mockGod.getSystemVariableManager()).andReturn(mockSystemVariableManager).anyTimes();
expect(mockSystemVariableManager.getSystemVariable(CYCLIC_PROCESS_LISTENER_HEART_BEAT_TOLERANCE, "30000"))
.andReturn("30000").anyTimes();
}

private void mockLogger() {
logger = addMock(Logger.class);
logger.info(isA(String.class)); expectLastCall().atLeastOnce();
logger.debug(isA(String.class)); expectLastCall().atLeastOnce();
}
}



Test Readability
To design is to communicate clearly by
whatever means you can control or
master.
—Milton Glaser


Test Names
Describe Features
public class TargetObjectTest {
@Test public void isReady() {

✘
@Test public void choose() {
@Test public void choose1() {

public class TargetObject {
public void isReady() {
public void choose(Picker picker) {


Test Names
Describe Features

public class ListTests {
@Test public void
holdsItemsInTheOrderTheyWereAdded() {
@Test public void
canHoldMultipleReferencesToTheSameItem() {
@Test public void
throwsAnExceptionWhenRemovingAnItemItDoesntHold() {



Canonical Test Structure

public class StringTemplateTest {
@Test public void expandsMacrosSurroundedWithBraces() {
StringTemplate template = new StringTemplate("{a}{b}"); Setup
HashMap<String,Object> macros = new HashMap<String,Object>();
macros.put("a", "A"); macros.put("b", "B");

String expanded = template.expand(macros); Execute

assertThat(expanded, equalTo("AB")); Assert
Teardown
}
}


Streamline the Test Code

assertThat(instruments,
hasItem(instrumentWithPrice(greaterThan(81))));



Narrow Assertions and
Expectations

oneOf(failureReporter).cannotTranslateMessage(
with(SNIPER_ID), with(badMessage),
with(any(RuntimeException.class)));


Self-Describing Variables

final static Chat UNUSED_CHAT = null;

final static int INVALID_ID = 666;



@RunWith(NestedJUnit4.class)
public class RemovingFullRowsTest extends Assert {
private static final RotatableGrid PIECE =
new RotatablePiece(
"" +
".X.n" +
".X.n" +
".X.n");

  private final RowRemovalListener listener =
mock(RowRemovalListener.class);
  private Board board;

  private void dropAndFallToBottom(RotatableGrid piece) {
   board.drop(piece);
    while (board.hasFalling()) {
     board.tick();
    }
  }
[...]

http://www.cs.helsinki.fi/u/luontola/tdd-2009/harjoitukset

public class When_many_rows_become_full_at_the_same_time {
@Before
public void dropPiece() {
board = new Board("" +
"........n" +
"........n" +
"AAAA.AAAn" +
"BBBB..BBn" +
"CCCC.CCCn");
board.addRowRemovalListener(listener);
dropAndFallToBottom(PIECE);
}

@Test
public void all_of_those_rows_are_removed() {
String s = board.toString();
assertFalse("Should not contain 'A':n" + s, s.contains("A"));
assertFalse("Should not contain 'C':n" + s, s.contains("C"));
}

   @Test
public void the_row_removal_listener_is_notified_about_the_removed_rows() {
verify(listener).onRowsRemoved(2);
   }
}


Constructing
Complex Test Data
Many attempts to communicate are
nulliﬁed by saying too much.
—Robert Greenleaf

The Problem With
Object Structures
Order order = new Order(
new Customer("Sherlock Holmes",
new Address("221b Baker Street",
"London",
new PostCode("NW1", "3RX"))));
order.addLine(new OrderLine("Deerstalker Hat", 1));
order.addLine(new OrderLine("Tweed Cape", 1));

Order order1 = ExampleOrders.newDeerstalkerAndCapeAndSwordstickOrder();
Order order2 = ExampleOrders.newDeerstalkerAndBootsOrder();



Test Data Builder:
Add Indirection
public class OrderBuilder {
private Customer customer = new CustomerBuilder().build();
private List<OrderLine> lines = new ArrayList<OrderLine>();
private BigDecimal discountRate = BigDecimal.ZERO;

public OrderBuilder withCustomer(Customer customer) {
this.customer = customer;
return this;
}
public OrderBuilder withOrderLines(OrderLines lines) {
this.lines = lines;
return this;
}
public OrderBuilder withDiscount(BigDecimal discountRate) {
this.discountRate = discountRate;
return this;
}
public Order build() {
Order order = new Order(customer);
for (OrderLine line : lines) order.addLine(line);
order.setDiscountRate(discountRate);
return order;
}
}

Only Need To Include
Relevant Values

new OrderBuilder()
.fromCustomer(
new CustomerBuilder()
.withAddress(new AddressBuilder().withNoPostcode().build())
.build())
.build();



Named Methods Make
Mistakes Obvious

new AddressBuilder()
.withStreet("221b Baker Street")
.withStreet2("London")
.withPostCode("NW1 6XE")
.build();


Use Builders to
Create Similar Objects
OrderBuilder hatAndCape = new OrderBuilder()
.withLine("Deerstalker Hat", 1)
.withLine("Tweed Cape", 1);

Order orderWithDiscount = hatAndCape
.but().withDiscount(0.10).build();
Order orderWithGiftVoucher = hatAndCape
.but().withGiftVoucher("abc").build();



Compacting Construction

Order order = anOrder()
.from(aCustomer()
.with(anAddress().withNoPostcode()))
.build();

Address aLongerAddress = anAddress()
.withStreet("221b Baker Street")
.withCity("London")
.with(postCode("NW1", "3RX"))
.build();


Refactor To Builders
@Test public void reportsTotalSalesOfOrderedProducts() {
sendAndProcess(anOrder()
.withLine("Tweed Cape", 1));
sendAndProcess(anOrder().withLine("Deerstalker Hat", 1));

TotalSalesReport report = gui.openSalesReport();
report.checkDisplayedTotalSalesFor("Deerstalker Hat", is(equalTo(2)));
report.checkDisplayedTotalSalesFor("Tweed Cape", is(equalTo(1)));

void sendAndProcess(OrderBuilder orderDetails) {
Order order = orderDetails
.withDefaultCustomersReference(nextCustomerReference())
.build();
requestSender.send(order);
progressMonitor.waitForCompletion(order);
}



What, Not How
@Test public void reportsTotalSalesOfOrderedProducts() {
havingReceived(anOrder()
.withLine("Tweed Cape", 1));
havingReceived(anOrder().withLine("Deerstalker Hat", 1));

TotalSalesReport report = gui.openSalesReport();
report.displaysTotalSalesFor("Deerstalker Hat", equalTo(2));
report.displaysTotalSalesFor("Tweed Cape", equalTo(1));
}


Test Diagnostics

Mistakes are the portals of discovery.

—James Joyce


Explain Yourself

assertEquals(16301, customer.getBalance());

ComparisonFailure: expected:<[16301]> but was:<[16103]>

assertEquals("balance", 16301, customer.getBalance());

ComparisonFailure: balance expected:<[16301]> but was:<[16103]>


Describe Yourself
ComparisonFailure: expected:<[a customer account id]>
but was:<[id not set]>

java.lang.AssertionError: payment date
Expected: <Thu Jan 01 01:00:01 GMT 1970>
got: <Thu Jan 01 01:00:02 GMT 1970>

Date startDate = namedDate(1000, "startDate");
Date endDate = namedDate(2000, "endDate");

Date namedDate(long timeValue, final String name) {
return new Date(timeValue) {
public String toString() { return name; }
};
}
java.lang.AssertionError: payment date
Expected: <startDate>
got: <endDate>



Tracer Objects
@RunWith(JMock.class) public class CustomerTest {
final LineItem item1 = context.mock(LineItem.class, "item1");
final LineItem item2 = context.mock(LineItem.class, "item2");
final Billing billing = context.mock(Billing.class);

@Test public void requestsInvoiceForPurchasedItems() {
context.checking(new Expectations() {{
oneOf(billing).add(item1);
oneOf(billing).add(item2);
}});
customer.purchase(item1, item2);
customer.requestInvoice(billing);
}
}
not all expectations were satisfied
expectations:
expected once, already invoked 1 time: billing.add(<item1>)
! expected once, never invoked: billing.add(<item2>>)
what happened before this:
billing.add(<item1>)



Test Flexibility
Living plants are ﬂexible and tender;
the dead are brittle and dry.
[...]
The rigid and stiff will be broken.
The soft and yielding will overcome.
—Lao Tzu (c.604—531 B.C.)

Specify Precisely
What Should Happen
and No More



Interlude

Information,
Not Representation
public interface CustomerBase {
// Returns null if no customer found
Customer findCustomerWithEmailAddress(String emailAddress);

allowing(customerBase).findCustomerWithEmailAddress(theAddress);
will(returnValue(null));

public static final Customer NO_CUSTOMER_FOUND = null;

public interface CustomerBase {
Maybe<Customer> findCustomerWithEmailAddress(String emailAddress);
}



Precise Assertions
assertThat(“strike price”,
92, equalTo(instrument.getStrikePrice()));

assertThat(“transaction id”,
instrument.getTransactionId(),
largerThan(PREVIOUS_TRANSACTION_ID));

assertThat(failureMessage,
allOf(containsString("strikePrice=92"),
containsString("id=FGD.430"),
containsString("is expired")));


Precise Expectations

oneOf(auction).addAuctionEventListener(with(sniperForItem(itemId)));

oneOf(auditTrail).recordFailure(with(
allOf(containsString("strikePrice=92"),
containsString("id=FGD.430"),
containsString("is expired"))));



Allow Queries
Expect Commands

ignoring(auditTrail);
allowing(catalog).getPriceForItem(item); will(returnValue(74));

exactly(2).of(order).addItem(item, 74);


Only Enforce Order
When It Matters

@Test public void announcesMatchForOneAuction() {
final AuctionSearcher auctionSearch =
new AuctionSearcher(searchListener, asList(STUB_AUCTION1));

context.checking(new Expectations() {{
Sequence events = context.sequence("events");
oneOf(searchListener).searchMatched(STUB_AUCTION1); inSequence(events);
oneOf(searchListener).searchFinished(); inSequence(events);
}});

auctionSearch.searchFor(KEYWORDS);
}



“Guinea Pig” Objects
public class XmlMarshallerTest {
public static class MarshalledObject {
private String privateField = "private";
public transient String transientField = "transient";
public final String publicFinalField = "public final";
// constructors, accessors for private field, etc.
}

@Test public void marshallsAndUnmarshallsSerialisableFields() {
XMLMarshaller marshaller = new XmlMarshaller();
MarshalledObject original = new MarshalledObject();
String xml = marshaller.marshall(original);
MarshalledObject unmarshalled = marshaller.unmarshall(xml);
assertThat(unmarshalled,
hasSameSerialisableFieldsAs(original));
}
}


Tests Are Code Too

• Expressiveness over convenience
• Refactor and abstract
• Focus on what matters
• If it’s hard to test, that’s a clue



Other sources


And, of course…


Sustaining Test-Driven Development

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