Excuse me, sir, do you have a moment to talk about tests in Kotlin

Excuse me, sir,
do you have a
moment to talk
about tests in
Kotlin?
—
Leonid Rudenko

Why?
—
Selenium Camp 2016
#4 Make Your Automation ier
_4

What’s going on here
—
• What is Kotlin?
• Problems Kotlin solves
• Demo
Excuse me, sir, do you have a moment to talk about tests in Kotlin? _5

—
• What is Kotlin?
• Demo

Kotlin is...
—
• JVM language from JetBrains – Java 6+
1. What is Kotlin? _7

Kotlin is...
—
• JVM language
• Statically typed

Kotlin is...
—
• JVM language
• Multi-paradigm – OOP & functional

Kotlin is...
—
• JVM language
• Multi-paradigm
• Pragmatic

Kotlin is...
—
• JVM language
• Multi-paradigm
• Pragmatic
• Democratic

Kotlin is...
—
• JVM language
• Multi-paradigm
• Pragmatic
• Democratic
• Safe

Kotlin is...
—
• JVM language
• Multi-paradigm
• Pragmatic
• Democratic
• Safe
• Concise
Brevity is the sister of talent.
- Anton Chekhov -

Kotlin is...
—
• JVM language
• Multi-paradigm
• Pragmatic
• Democratic
• Safe
• Concise
• Interoperable

Kotlin 1.0
—
• 15 Feb 2016 – backward compatibility

Kotlin 1.0
—
• 15 Feb 2016
• kotlinc, Intellij IDEA (plugin), Eclipse (plugin), NetBeans (plugin)

Kotlin 1.0
—
• 15 Feb 2016
• kotlinc, Intellij IDEA (plugin), Eclipse (plugin), NetBeans (plugin)
• Open source https://github.com/jetbrains/kotlin

Google Trends: Kotlin 1y
—

Google Trends: Kotlin vs Groovy 1y
—

Where Kotlin is used
—
• JetBrains products

—
• Android

—
• Android
• Server & Desktop

—
• Android
• Gradle 3.0 https://github.com/gradle/gradle-script-kotlin

—
• Android
• Gradle 3.0
• (Web) Test Automation

Test Automation: why Kotlin?
—
• Syntax similar to Java

—
• Clean test code
Conciseness
Easy to read == easy to understand
Collective code ownership, effective code review

—
• Clean test code
Conciseness
Easy to read == easy to understand
Collective code ownership, effective code review
• Safe test code

—
• What is Kotlin?
• Demo

Kotlin features
—
• Extension functions
• Data classes
• Lambda functions
• Smart cast
• Type inference
• Null safety
2. Problems Kotlin solves _32

1. Problem: Maps and Lists in Java
—
// Java
Map<Integer, Credentials> users = new HashMap<>();
users.put(1, new Credentials("vasya", "123456"));
users.put(2, new Credentials("johny", "qwerty"));
users.put(3, new Credentials("admin", "admin"));
List<Integer> responseCodes = new ArrayList<>();
responseCodes.add(200);
responseCodes.add(302);

1. Solution: Kotlin collections
—
// Kotlin
val users = mapOf(
1 to Credentials("vasya", "123456"),
2 to Credentials("johny", "qwerty"),
3 to Credentials("admin", "admin"))
val responseCodes = listOf(200, 302)

1. Collections: Map
—
// Kotlin
val users = mapOf(
1 to Credentials("vasya", "123456"),
2 to Credentials("johny", "qwerty"),
3 to Credentials("admin", "admin"))
Map<Integer, Credentials>
new
users.put(4, Credentials("...", "..."))

1. Collections: Traversing a map
—
// Java
for (Map.Entry<Integer, Credentials> pair : users.entrySet()) {
System.out.println(pair.getKey() + "->" + pair.getValue());
}
// Kotlin
for ((id, creds) in users) {
println("$id->$creds")
}

1. Collections: forEach, filters, sorting...
—
// Kotlin
val link = driver.findElements("a").firstOrNull {
it.text == "Selenium Camp"
}

1. Collections: Java & Groovy
—
• Java 7
• Java 8 (Stream API)
• Groovy

1. Collections: forEach, filters, sorting...
—
// Kotlin
val link = driver.findElements("a").firstOrNull {
it.text == "Selenium Camp"
}

2. Problem: framework can’t do what you need it to do
—
// Java
public static List<WebElement> findElements(WebDriver driver,
String selector) {
return driver.findElements(By.cssSelector(selector));
}
findElements(driver, "a");

2. Problem: framework can’t do what you need it to do
—

2. Solution: Extension functions
—
// Kotlin
fun WebDriver.findElements(selector: String): List<WebElement>{
return this.findElements(By.cssSelector(selector))
}
driver.findElements("a")

2. Extension functions
—
// Kotlin
}

—
// Kotlin
}

2. Extension functions: Java & Groovy
—
• Java
• Groovy (Extension Modules)

3. Problem: small classes are not small
—
// Java
public class Credentials {
private final String username;
private final String password;
}

—
// Java
public Credentials(String username, String password) {
this.username = username;
this.password = password;
}
}

—
// Java
}
public String getUsername() { return username; }
public String getPassword() { return password; }
}

—// Java
}
@Override
public String toString() {
return username + '/' + password;
}
}

—// Java
}
@Override
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Credentials that = (Credentials) o;
if (username != null ? !username.equals(that.username) : that.username != null) return false;
return password != null ? password.equals(that.password) : that.password == null;
}
@Override
public int hashCode() {
int result = username != null ? username.hashCode() : 0;
return 31 * result + (password != null ? password.hashCode() : 0);
}
}

3. Problem: 27 lines
—// Java
}
@Override
}
@Override
if (username != null ? !username.equals(that.username) : that.username != null) return false;
}
@Override
}
}

3. Solution: direct to Kotlin – 18 lines
—// Java
}
@Override
}
@Override
if (username != null ? !username.equals(that.username) : that.username != null)
return false;
}
@Override
}
}
// Kotlin
class Credentials {
private val username: String
private val password: String
constructor(username: String, password: String) {
this.username = username
this.password = password
}
fun getUsername(): String { return username }
fun getPassword(): String { return password }
override fun toString() = username + '/' + password
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (other?.javaClass != javaClass) return false
other as Credentials
return username == other.username && password == other.password
}
override fun hashCode() = 31 * username.hashCode() + password.hashCode()
}

3. Solution: remove getters – 16 lines
—// Kotlin
class Credentials {
val username: String
val password: String
constructor(username: String, password: String) {
this.username = username
this.password = password
}
//fun getUsername(): String { return username }
//fun getPassword(): String { return password }
}
}

3. Solution: primary constructor – 10 lines
—// Kotlin
class Credentials(val username: String, val password: String) {
//val username: String
//val password: String
//constructor(username: String, password: String) {
// this.username = username
// this.password = password
//}
}
}

3. Solution: data class – 1 line
—
// Kotlin
data class Credentials(val username: String, val password: String) {
//override fun toString() = username + '/' + password
//override fun equals(other: Any?): Boolean {
// if (this === other) return true
// if (other?.javaClass != javaClass) return false
// other as Credentials
// return username == other.username && password == other.password
//}
//override fun hashCode() = 31 * username.hashCode() + password.hashCode()
}

3. Solution: Kotlin data classes
—
// Kotlin
data class Credentials(val username: String, val password: String)
val creds = Credentials("a", "b")
println(creds.username) // a
creds.username = "you can't do that"
println(creds) // Credentials(username=a, password=b)
println(creds == Credentials("a", "b")) // true

3. Solution: Kotlin data classes
—
// Kotlin
data class Credentials(val username: String, val password: String) {
override fun toString(): String {
return "$username/$password"
}
}
println(Credentials("one", "two")) // one/two

3. Data classes: Java & Groovy
—
• Java (Lombok https://projectlombok.org/)
• Groovy (@groovy.transform.Canonical)

4. Problem: steps in Allure report
—
// Java
driver.findElement("button").click();

4. Problem: steps in Allure report
—
// Java
@Step("Click the button")
public void clickButton() {
}
clickButton();

4. Solution: steps in Allure report
—
// Java 8
@Step("{0}")
public void step(String title, Runnable code) {
code.run();
}
step("Click the button", () -> {
});

4. Solution: steps in Allure report
—
// Kotlin
@Step("{0}")
fun step(title: String, code: () -> Any) = code()
step("Click the button") {
driver.findElement("button").click()
}

4. Solution: just compare
—
// Java 8
step("Click the button", () -> {
// your code here
});
// Kotlin
step("Click the button") {
// your code here
}

4. Steps in Allure report: Java & Groovy
—
• Java 7
• Java 8
• Groovy

5. Problem: checked exceptions
—
// Java
URLDecoder.decode(param, "UTF-8");

// Java
URLDecoder.decode(param, "UTF-8");
// Kotlin
URLDecoder.decode(param, "UTF-8")
5. Solution: no checked exceptions
—

5. Checked exceptions: Java & Groovy
—
• Java
• Groovy

6. Problem: unchecked cast
—
// Java
Object results
= ((JavascriptExecutor) driver).executeScript("...");

// Java
Object results
if (results instanceof List) {
List<String> list = ((List<Object>) results)
.stream()
.filter(String.class::isInstance)
.map(String.class::cast)
.collect(toList());
}
—

// Java
Object results
if (results instanceof List) {
List<String> list = ((List<Object>) results)
}
—

// Kotlin
val results
= (driver as JavascriptExecutor).executeScript("...")
if (results is List<*>) {
val list = results.filterIsInstance<String>()
}
6. Solution: Kotlin smart cast
—

6. Unchecked cast: Java & Groovy
—
• Java
• Groovy

7. Problem: Java is verbose
—

7. Solution: Kotlin syntactic sugar
—
// Java
actualText.equals(expectedText)
// Kotlin
actualText == expectedText

7. Solution: String templates
—
// Java
String s = "date: " + date + " and author: " + USER.getName();
String s =
format("date: %s and author: %s", date, USER.getName());
// Kotlin
val s = "date: $date and author: ${USER.name}"

7. Solution: ranges
—
// Java
for (int i = 0; i <= 10; i += 2)
// Kotlin
for (i in 0..10 step 2)

7. Solution: Kotlin rich standard library
—
// Java
!list.isEmpty()
// Kotlin
list.isNotEmpty()

7. Solution: Kotlin type inference
—
// Java
final int i = 0;
final String s = "abc";
final List<String> list = new ArrayList<>();
// Kotlin
val i = 0
val s = "abc"
val list = listOf("a", "b", "c")

7. Verbosity: Java & Groovy
—
• Java
• Groovy

8. Problem: java.lang.NullPointerException
—

8. Solution: Null safety
—
var username: String
username = null // compilation error

8. Null safety
—
var username: String
username = null // compilation error
var username: String?
username = null // ok

8. Null safety
—
var username: String // non-nullable String
username = null
var username: String? // nullable String
username = null

8. Null safety: safe call
—
var username: String? = "Vasya"
var count = username.length // compilation error

8. Null safety: safe call
—
var username: String? = "Vasya"
var count = username?.length // ok, count is 5
username = null
var count = username?.length // ok, count is null

8. Null safety: Elvis operator
—
input.sendKeys(username ?: "Guest")
var images = findAllImagesOnPage()
?: throw AssertionError("No images")
?:

8. Null safety: Java & Groovy
—
• Null safety: Java (Optional<T> in Java8), Groovy
• Safe call: Java, Groovy
• Elvis operator: Java, Groovy

Java vs Groovy vs Kotlin
—
1 2 3 4 5 6 7 8
Java 7 – – – – – – – –
Java 8 ± – – + – – – –
Groovy + ± + + + – + –
Kotlin + + + + + + + +

Why not Groovy?
—
• Not statically typed: runtime bugs
• Not statically typed: performance
• Not statically typed: IDE support
• No null safety

—
• What is Kotlin?
• Demo

Example test project in Kotlin
—
• JUnit http://junit.org/junit4/
• Html Elements https://github.com/yandex-qatools/htmlelements
• Allure Framework https://github.com/allure-framework/
• Gradle https://gradle.org/
• gradle-docker-plugin https://github.com/bmuschko/gradle-docker-plugin
3. Demo _93

https://github.com/leonsabr/seleniumcamp-kotlin-demo
—
3. Demo _94
• Kotlin + { Gradle, JUnit, Selenium, Html Elements, Allure } = OK

—
3. Demo _95
• Kotlin + { Gradle, JUnit, Selenium, Html Elements, Allure }
• Java interoperability

—
3. Demo _96
java kotlin ∆
main 670 434 35,2%
test 92 84 8,7%
total 762 518 32%
• Kotlin + { Gradle, JUnit, Selenium, Html Elements, Allure }
• Java interoperability
• Conciseness (lines of code)

Useful links
—
• Reference http://kotlinlang.org/docs/reference/
• List of Kotlin resources https://kotlin.link/
• Try Kotlin online http://try.kotl.in/
• Slack https://kotlinlang.slack.com/
_97

Thank you
for your attention
—
jetbrains.com
leonid.rudenko@jetbrains.com
@leonsabr

Excuse me, sir, do you have a moment to talk about tests in Kotlin

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