Unit testing in Android involves testing individual units or components of an Android application to verify their correctness. This is done during development by the developer. The document discusses what unit testing involves, provides examples of unit tests for a number validator class and interval overlapping detector class, and discusses test doubles, constraints of unit testing in Android, where to unit test in an Android app, and test-driven development.

1. Unit Testing in Android
By Shamsul Arafin Mahtab
Software Engineer,
M2SYS Technology
Presentation Slide

2. What Should we know at first
2
➢ A type of software testing where individual units/ components
of a software are tested
➢ Done during the development (coding) of an application
➢ The objective of Unit Testing is to verify its correctness
➢ Usually performed by the developer
➢ Tools that we use in Android: JUnit4

3. What is Unit Testing’s Job
3
Ensuring that ‘the thing’ does what it is supposed to do

4. Code Structure in Android
4
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class NumberValidatorTest {
/** SystemUnderTest */
NumberValidator SUT;
@Before
public void setUp() throws Exception {
SUT = new NumberValidator();
}
/** Naming unitOfWork_stateUnderTest_expectedBehaviour */
@Test
public void checkPositive_correct_trueReturned() {
}
@After
public void tearDown() throws Exception {
}
}
Press Ctrl+Shift+T for a new Test class.

5. Example 1
5

6. Example 1 – Number Validator
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public class NumberValidatorTest {
NumberValidator SUT;
@Before
public void setUp() throws Exception {
SUT = new NumberValidator();
}
@Test
public void checkPositive_positive_trueReturned() {
boolean result = SUT.isPositiveNumber(2);
Assert.assertThat(result, CoreMatchers.is(true));
}
@Test
public void checkPositive_zero_falseReturned() {
boolean result = SUT.isPositiveNumber(0);
Assert.assertThat(result, CoreMatchers.is(false));
}
@Test
public void checkPositive_negative_falseReturned() {
boolean result = SUT.isPositiveNumber(-1);
Assert.assertThat(result, CoreMatchers.is(false));
}
}

7. Example 1 – Test Output
7
Current Implementation

8. Example 2 – Boundary Check
8

9. Example 2 – Overlapping Detector
9
Test Cases
1. Interval1 before Interval2 (False)
2. Interval1 overlaps Interval2 on start (True)
3. Interval1 contained on Interval2 (True)
4. Interval1 contains Interval2 (True)
5. Interval1 overlaps Interval2 on end (True)
6. Interval1 after Interval2 (False)
7. Interval1 adjacent to Interval2 on start (True)
8. Interval1 adjacent to Interval2 on end (True)

10. Example 2 – Overlapping Detector
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Run IntervalsOverlapDetectorTest with Coverage
Coverage Result

11. Introduction To Test Doubles
11

12. Why Test Double man!!
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But if you have dependencies…..

13. Test Double Summary
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➢ Used to substitute external unit dependencies in tests
➢ Three types of Test Doubles: Fake, Stub, Mock
➢ Fake: Functional implementation optimized for test
➢ Stub: Returns predefined data and can have programmable
behavior
➢ Mock: Records interactions with itself
➢ Mock is most used

14. List of Test Frameworks
14
Language Test Frameworks Mocking Frameworks
Java JUnit Mockito
Kotlin
Spek,
KotlinTest
Mockito-Kotlin,
MockK

15. Some Constraints
15
➢ Unit Test is not aware of Nullability
➢ Don’t use Singleton
➢ Static Methods has hidden dependencies, so can not be
substituted
➢ Can’t test on Android Frameworks

16. Where can we unit test in our app
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UI Layer
Application Layer
Domain Layer
Infrastructure Layer
Espresso Test

17. Black Box v White Box testing
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Black Box Testing
White Box Testing

18. Which one is better?
18

19. Test Driven Development to Rescue?
19

20. Uncle Bob’s Technique
20
1. You are not allowed to write any production code unless it is
to make a failing unit test pass
2. You are not allowed to write any more of a unit test than is
sufficient to fail and compilation failures are failures
3. You are not allowed to write any more production code than it
is sufficient to pass the one failing unit test

21. Your Decision
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Be honest, do you like it to do when you will implement?

22. My Decision after the study
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23. Thank You
23