If you've any experience with Java development, you've heard of or most probably worked with JUnit. It is a testing framework, for Java (as well as Kotlin).
Typically unit tests are created in a separate source folder than real source codes, to keep it separated. The standard Maven/Gradle convention uses src/main for real codes (Java/Kotlin files or classes) and src/test for test classes. The following screenshot shows the structure for the project we're using in this book:
Before beginning to write test cases we've to add the following Gradle dependencies:
testCompile 'junit:junit:4.12' testCompile "org.mockito:mockito-core:1.9.5" ...
