Unit testing with JUnit in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of unit testing?

Unit testing checks small parts of code, like functions or methods, to make sure they work correctly on their own.

beginner

In JUnit, what annotation marks a method as a test?

The @Test annotation tells JUnit that the method below it is a test method to run.

beginner

What does the assertion assertEquals(expected, actual) do in a JUnit test?

It checks if the actual result matches the expected result. If they are not equal, the test fails.

intermediate

Why should unit tests be independent from each other?

Tests should not depend on others so that one test failing does not cause others to fail. This keeps tests reliable and easy to fix.

beginner

How do you run JUnit tests in an Android Kotlin project?

You run JUnit tests using Android Studio's test runner or Gradle commands. Tests run on the JVM without needing an Android device.

Which annotation is used to mark a method as a test in JUnit?

A @Test

B @Run

C @Check

D @Verify

The @Test annotation marks a method as a test method in JUnit.

What does assertTrue(condition) check in a JUnit test?

A That the condition is false

B That an exception is thrown

C That two values are equal

D That the condition is true

assertTrue(condition) checks if the condition is true; if not, the test fails.

Why is it important for unit tests to be fast?

A So they can run often and give quick feedback

B Because slow tests are more accurate

C To use more CPU resources

D To make debugging harder

Fast tests allow developers to run them frequently and get quick feedback on code changes.

Which of these is NOT a good practice in unit testing?

A Testing one thing per test

B Relying on external services in tests

C Making tests independent

D Using clear test names

Unit tests should not rely on external services to avoid flakiness and keep tests fast.

In Android Kotlin projects, where are JUnit unit tests usually placed?

A src/androidTest/java

B src/main/java

C src/test/java

D src/resources

JUnit unit tests are placed in src/test/java to run on the JVM without an Android device.

Explain how to write a simple JUnit test method in Kotlin for a function that adds two numbers.

Think about the structure: annotation, method, call, assertion.

Describe why unit tests are important in Android app development and how JUnit helps.

Focus on benefits and JUnit features.