This document provides an overview of various testing frameworks and concepts used for Android testing. It discusses JUnit, Mockito, PowerMock, Robolectric, and Espresso - the most popular tools for unit, integration, and UI testing of Android apps. For each tool, it provides brief descriptions of their purpose and capabilities. It also includes examples demonstrating how to write tests using JUnit, Mockito, and PowerMock. The document aims to explain what these testing tools are and how they can be used for testing Android applications.

1. Android Testing
Sean Tsai
2017

2. JUnit
Mockito
PowerMock EasyMock
Robolectric
AssertJ
HamcrestTest
Espresso

3. What are all this…?

4. JUnit
● Unit testig framework for Java
● Stable Version - 4
● JUnit 4 - Still the standard version for Android
● Ports
○ C (CUnit)
○ JavaScript (JSUnit)
○ Objective-C (OCUnit)
○ Ruby (Test::Unit)
○ …

5. JUnit 5
● Released on September 10, 2017
● JUnit Platform + JUnit Jupiter + JUnit Vintage
● Requires Java 8 at runtime
● Support for lambda expressions to be used in assertions
● New Annotations:
○ @BeforeEach, @AfterEach (equivalent to the previous @Before and @After)
○ @BeforeAll, @AfterAll (equivalent to the previous @BeforeClass and @AfterClass)
○ @Disabled (equivalent to the previosu @Ignore)
● Assumptions
● Tagging
● Nested Tests
● Repeated Tests
● Dependency Injection for Constructors and Methods
● Parameterized Tests

6. JUnit Example
@Test
public void isVIP() throws Exception {
Customer customer = new Customer(1, "Sean");
customer.setLevel(11);
Assert.assertTrue(CustomerUtils.isVIP(customer));
}

7. EasyMock
import static org.easymock.classextension.EasyMock.*;
List mock = createNiceMock(List.class);
expect(mock.get(0)).andStubReturn("one");
expect(mock.get(1)).andStubReturn("two");
mock.clear();
replay(mock);
● Current version: 3.4 (2001 - 2015)
● 3.5 (2017)
● The framework allows the creation of test double objects for the purpose of TDD or BDD.

8. Mockito
● From 2008 - Now
● Based on EasyMock
● Current version: Mockito 2
○ Mock make engine: CGLIB -> ByteBuddy
○ Remove Hamcrest from dependacy.
○ Java 8 support.
○ anyX() and any(SomeType.class) matchers now reject nulls and check type
Ref: https://github.com/mockito/mockito

9. Mockito Example - Let's verify some behaviour!
public class MockitoTest {
@Test
public void test1_verify() {
//mock creation
List mockedList = mock(List.class);
//using mock object
mockedList.add("one");
mockedList.clear();
//verification
verify(mockedList).add("one");
verify(mockedList).clear();
}
}

10. Mockito Example - How about some stubbing?
@Test (expected = RuntimeException.class)
public void test2_stub() {
//You can mock concrete classes, not just interfaces
LinkedList mockedList = mock(LinkedList.class);
//stubbing
when(mockedList.get(0)).thenReturn("first");
when(mockedList.get(1)).thenThrow(new RuntimeException());
//following prints "first"
System.out.println(mockedList.get(0));
//following throws runtime exception
System.out.println(mockedList.get(1));
//following prints "null" because get(999) was not stubbed
System.out.println(mockedList.get(999));
verify(mockedList).get(0);
}

11. Mockito Example - Argument matchers
@Test
public void test3_argumentMatchers() {
//You can mock concrete classes, not just interfaces
LinkedList mockedList = mock(LinkedList.class);
//stubbing using built-in anyInt() argument matcher
when(mockedList.get(anyInt())).thenReturn("element");
//stubbing using custom matcher (let's say isValid() returns your own matcher implementation):
// when(mockedList.contains(argThat(isValid()))).thenReturn("element");
//following prints "element"
System.out.println(mockedList.get(999));
//you can also verify using an argument matcher
verify(mockedList).get(anyInt());
//argument matchers can also be written as Java 8 Lambdas
// verify(mockedList).add(argThat(someString -> someString.length() > 5));
}

12. Mockito Example - Verifying exact number of invocations
@Test
public void test4_verifyingExactNumberOfInvocations() {
//You can mock concrete classes, not just interfaces
LinkedList mockedList = mock(LinkedList.class);
//using mock
mockedList.add("once");
mockedList.add("twice");
mockedList.add("twice");
mockedList.add("three times");
mockedList.add("three times");
mockedList.add("three times");
//following two verifications work exactly the same - times(1) is used by default
verify(mockedList).add("once");
verify(mockedList, times(1)).add("once");
//exact number of invocations verification
verify(mockedList, times(2)).add("twice");
verify(mockedList, times(3)).add("three times");
//verification using never(). never() is an alias to times(0)
verify(mockedList, never()).add("never happened");
//verification using atLeast()/atMost()
verify(mockedList, atLeastOnce()).add("three times");
verify(mockedList, atLeast(2)).add("three times");
verify(mockedList, atMost(5)).add("three times");

13. Mockito Example - Stubbing void methods with
exceptions
@Test (expected = RuntimeException.class)
public void test5_StubbingVoidMethodsWithExceptions() {
//You can mock concrete classes, not just interfaces
LinkedList mockedList = mock(LinkedList.class);
doThrow(new RuntimeException()).when(mockedList).clear();
//following throws RuntimeException:
mockedList.clear();
}

14. Mockito Example - Verification in order
@Test
public void test6_verificationInOrder () {
// A. Single mock whose methods must be invoked in a particular order
List singleMock = mock(List.class);
//using a single mock
singleMock.add( "was added first" );
singleMock.add( "was added second" );
//create an inOrder verifier for a single mock
InOrder inOrder = inOrder(singleMock) ;
//following will make sure that add is first called with "was added first, then with "was added second"
inOrder.verify(singleMock).add( "was added first" );
inOrder.verify(singleMock).add( "was added second" );
// B. Multiple mocks that must be used in a particular order
List firstMock = mock(List.class);
List secondMock = mock(List.class);
//using mocks
firstMock.add( "was called first" );
secondMock.add( "was called second" );
//create inOrder object passing any mocks that need to be verified in order
InOrder inOrder2 = inOrder(firstMock , secondMock) ;
//following will make sure that firstMock was called before secondMock
inOrder2.verify(firstMock).add( "was called first" );
inOrder2.verify(secondMock).add( "was called second" );
}

15. There are a lot more useful methods...
Ref: http://static.javadoc.io/org.mockito/mockito-core/2.10.0/org/mockito/Mockito.html#verification

16. PowerMock
● Enable mocking of static methods, constructors, final classes and methods, private methods.
● Depends on Junit and Mockito.
● Support Mockito 2.8.x with PowerMock 1.7.0-1.7.1.
Ref:
1. https://github.com/powermock/powermock/wiki/Downloads
2. https://github.com/powermock/powermock/wiki/Mockito

17. PowerMock Example - Mock static
@RunWith(PowerMockRunner.class)
@PrepareForTest(CustomerUtils.class)
public class OrderTest {
private Customer customer;
@Before
public void setUp() throws Exception {
customer = new Customer(1, "Sean");
customer.setLevel(11);
}
@Test
public void getTotal() throws Exception {
PowerMockito.mockStatic(CustomerUtils.class);
Mockito.when(CustomerUtils.isVIP(any(Customer.class))).thenReturn(true);
Order order = new Order(1, customer);
order.setOriginalTotal(10);
Assert.assertEquals(8f, order.getTotal());
}
}

18. Roboletric
● A unit test framework that de-fangs the Android SDK jar so you can test-drive the development of
your Android app.
○ SDK, Resources, & Native Method Emulation
○ Run Tests Outside of the Emulator
○ No Mocking Frameworks Required

19. Roboletric Example
@RunWith(RobolectricTestRunner.class)
@Config(constants = BuildConfig.class)
public class MainActivityTest {
@Test
public void test_textView() {
MainActivity activity = Robolectric.setupActivity(MainActivity.class);
TextView results = (TextView) activity.findViewById(R.id.text);
Assert.assertEquals("Hello World!", results.getText().toString());
}
}

20. Espresso
@Test
public void greeterSaysHello() {
onView(withId(R.id.name_field)).perform(typeText("Steve"));
onView(withId(R.id.greet_button)).perform(click());
onView(withText("Hello Steve!")).check(matches(isDisplayed()));
}
● Android UI tests.

21. Test Double

22. Dummy Object
public Customer createDummyCustomer() {
County county = new County("Essex");
City city = new City("Romford", county);
Address address = new Address("1234 Bank Street", city);
Customer customer = new Customer("john", "dobie", address);
return customer;
}
@Test
public void addCustomerTest() {
Customer dummy = createDummyCustomer();
AddressBook addressBook = new AddressBook();
addressBook.addCustomer(dummy);
assertEquals(1, addressBook.getNumberOfCustomers());
}

23. Dummy Object - Using Mockito
@Test
public void addCustomerWithDummyTest() {
Customer dummy = mock(Customer.class);
AddressBook addressBook = new AddressBook();
addressBook.addCustomer(dummy);
Assert.assertEquals(1, addressBook.getNumberOfCustomers());
}

24. Test stub - Responder
public class SimplePricingService implements PricingService {
PricingRepository repository;
public SimplePricingService(PricingRepository pricingRepository) {
this.repository = pricingRepository;
}
@Override
public Price priceTrade(Trade trade) {
return repository.getPriceForTrade(trade);
}
@Override
public Price getTotalPriceForTrades(Collection<trade> trades) {
Price totalPrice = new Price();
for (Trade trade : trades) {
Price tradePrice = repository.getPriceForTrade(trade);
totalPrice = totalPrice.add(tradePrice);
}
return totalPrice;
}
}

25. Test stub - Responder
@Test
public void testGetHighestPricedTrade() throws Exception {
Price price1 = new Price(10);
Price price2 = new Price(15);
Price price3 = new Price(25);
PricingRepository pricingRepository = mock(PricingRepository.class);
when(pricingRepository.getPriceForTrade(any(Trade.class)))
.thenReturn(price1, price2, price3);
PricingService service = new SimplePricingService(pricingRepository);
Price totalPrice = service.getTotalPricedTrade(getTrades());
assertEquals(50, totalPrice.getAmount());
}

26. Mock Object
@Mock
TradeRepository tradeRepository;
@Mock
AuditService auditService;
@Test
public void testAuditLogEntryMadeForNewTrade() throws Exception {
Trade trade = new Trade("Ref 1", "Description 1");
when(tradeRepository.createTrade(trade)).thenReturn(anyLong());
TradingService tradingService
= new SimpleTradingService(tradeRepository, auditService);
tradingService.createTrade(trade);
verify(auditService).logNewTrade(trade);
}

27. Test Spy
@Test
public void spy() {
List list = new LinkedList();
List spy = spy(list);
//optionally, you can stub out some methods:
when(spy.size()).thenReturn(100);
//using the spy calls *real* methods
spy.add("one");
spy.add("two");
//prints "one" - the first element of a list
System.out.println(spy.get(0));
//size() method was stubbed - 100 is printed
System.out.println(spy.size());
//optionally, you can verify
verify(spy).add("one");
verify(spy).add("two");
}

28. Fake Object
public void testReadWrite_inMemory() throws Exception{
// Setup:
FlightMgmtFacadeImpl facade = new FlightMgmtFacadeImpl();
facade.setDao(new InMemoryDatabase());
// Exercise:
AirPort yyc = facade.createAirport("YYC", "Calgary", "Calgary");
AirPort lax = facade.createAirport("LAX", "LAX Intl", "LA");
facade.createFlight(yyc, lax);
List flights = facade.getFlightsByOriginAirport(yyc);
// Verify:
assertEquals( "# of flights", 1, flights.size());
Flight flight = (Flight) flights.get(0);
assertEquals( "origin", "YYC", flight.getOrigin().getCode());
}

29. Fake Object
public class InMemoryDatabase implements FlightDao {
private List airports = new Vector();
public Airport createAirport(String airportCode, String name, String nearbyCity)
throws DataException, InvalidArgumentException {|-------10-------- 20-------- 30-------- 40-------- 50-------- 60----
assertParamtersAreValid(airportCode, name, nearbyCity);
assertAirportDoesntExist(airportCode);
Airport result = new Airport(getNextAirportId(),airportCode, name, createCity(nearbyCity));
airports.add(result);
return result;
}
public Airport getAirportByPrimaryKey(BigDecimal airportId)
throws DataException, InvalidArgumentException {
assertAirportNotNull(airportId);
Airport result = null;
Iterator i = airports.iterator();
while (i.hasNext()) {
Airport airport = (Airport) i.next();
if (airport.getId().equals(airportId)) {
return airport;
}
}
throw new DataException("Airport not found:" + airportId);
}
}

30. Q & A