Kotlin is a statically typed programming language that targets the JVM, Android, JavaScript, and Native. It's an open source project under the Apache 2.0 license. Kotlin is also a functional programming language with higher-order functions. Developers can use Kotlin with all existing Java libraries and frameworks.
Test-driven development is a development methodology which dictates that tests should be written before code is written. The purpose of this is to ensure that the code satisfies the requirements specified by the test. This methodology is also intended to make code more robust and easier to refactor.
Kotlin is a very concise language, which can lead to less code overall. This is important for writing tests, as the more code there is, the more time it takes to write tests for all of the functionality. In addition, Kotlin has null safety built in, which helps to avoid null pointer exceptions. This is especially important in tests, as any null pointers will cause the test to fail.
Assuming that you have already installed the Kotlin plugin for your IDE, create a new Kotlin project. When prompted, choose "Java" as the project template. For this guide, we will be using the Gradle build system.
Now that we have a project set up, let's write our first test. We'll start by creating a file in the src/test/kotlin
directory called MyFirstTest.kt
. In this file, we'll write a test to check that Kotlin's sum
function works as expected:
import org.junit.Assert.*
import org.junit.Test
class MyFirstTest {
@Test
fun testSum() {
assertEquals(4, sum(2, 2))
}
}
Here, we've imported the junit
library, which we'll use for writing our tests. We've also created a MyFirstTest
class, which contains a single testSum
method. This method uses the assertEquals
function to check that the result of calling sum
with the arguments 2
and 2
is equal to 4
.
To run this test, right-click on the MyFirstTest.kt
file and select "Run 'MyFirstTest'". You should see the test run and pass.
Now that we have a failing test, it's time to write the code to make it pass. Create a file in the src/main/kotlin
directory called MyFirst.kt
. In this file, we'll write the sum
function:
fun sum(a: Int, b: Int): Int {
return a + b
}
Now if you re-run the test, it should pass.
In this article, we've seen how to set up a Kotlin project for TDD and how to write our first test and code to make it pass. TDD is a great way to ensure that your code is correct and easy to refactor. Kotlin's concise syntax and built-in null safety make it an ideal language for TDD.