Java → kotlin: Tests Made Simple

Java → Kotlin:
Tests Made
Simple
—
Leonid Rudenko

• Reference http://kotlinlang.org/docs/reference/
_5
Useful links
—

• List of Kotlin resources https://kotlin.link/
_6
Useful links
—

• Try Kotlin online http://try.kotl.in/
_7
Useful links
—

• Try Kotlin online http://try.kotl.in/
• Slack https://kotlinlang.slack.com/
_8
Useful links
—

• Problems Kotlin solves
• Kotlin & Frameworks
• Demo
_9
What’s going on here
—

• Demo
_10
—

// 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);
_11
1. Problem: Collections in Java
—

// Java
List<String> classpath = new ArrayList<>();
classpath.add(getBundleJarPath());
classpath.addAll(getPluginsPath());
_12
1. allure-framework/allure1 https://git.io/v9RQZ
—

// Java
// Kotlin
val classpath = listOf(getBundleJarPath(), getPluginsPath())
_13
—

// Java
// Kotlin
List<String>
_14
—

// Java
// Kotlin
List<String>
classpath.add("/usr/bin")
_15
—

// Java
Map<TestItemIssueType, List<StatisticSubType>> types = new HashMap<>()
_16
1. reportportal/service-api https://git.io/v9RQy
—

// Java
{{
}};
_17
—

// Java
{{
put(AUTOMATION_BUG, Lists.newArrayList(
new StatisticSubType(AUTOMATION_BUG.getLocator(),
AUTOMATION_BUG.getValue(), "Automation Bug", "AB", "#f5d752")));
}};
_18
—

// Java
{{
put(AUTOMATION_BUG, Lists.newArrayList(
new StatisticSubType(AUTOMATION_BUG.getLocator(),
AUTOMATION_BUG.getValue(), "Automation Bug", "AB", "#f5d752")));
...
put(TO_INVESTIGATE, Lists.newArrayList(
new StatisticSubType(TO_INVESTIGATE.getLocator(),
TO_INVESTIGATE.getValue(), "To Investigate", "TI", "#ffa500")));
}};
_19
—

// Java
val types = mapOf(
AUTOMATION_BUG to listOf(StatisticSubType(AUTOMATION_BUG.locator,
AUTOMATION_BUG.value, "Automation Bug", "AB", "#f5d752")),
...
TO_INVESTIGATE to listOf(StatisticSubType(TO_INVESTIGATE.locator,
TO_INVESTIGATE.value, "To Investigate", "TI", "#ffa500")))
_20
—

_21
1. Collections: Traversing a map
—
// Java
for (Map.Entry<Integer, Credentials> pair : users.entrySet()) {
System.out.println(pair.getKey() + "->" + pair.getValue());
}
// Kotlin
users.forEach { k, v ->
println("$k->$v")
}

_22
1. allure-framework/allure1 https://git.io/v9R7E
—
// Java
List<String> names = new ArrayList<>();
for (File file : files) {
TestSuiteResult result
= JAXB.unmarshal(file, TestSuiteResult.class);
names.add(result.getName());
}

_23
1. allure-framework/allure1 https://git.io/v9R7E
—
// Java
List<String> names = new ArrayList<>();
for (File file : files) {
TestSuiteResult result
= JAXB.unmarshal(file, TestSuiteResult.class);
names.add(result.getName());
}
// Kotlin
val names = files.map {
JAXB.unmarshal(it, TestSuiteResult::class.java).name
}

• Java 7
• Java 8 (Stream API)
• Groovy
_24
1. Collections: Java & Groovy
—

_25
2. Problem: framework can’t do what you need it to do
—
// Java
public static void waitForElement(HtmlElement element, long
timeout) {
...
}
waitForElement(link, 10);
link.click();

_27
2. Problem: framework can’t do what you need it to do
—

_28
2. Solution: Extension functions
—
// Kotlin
fun <T : HtmlElement> T.waitForIt(timeout: Long = 5): T {
...
return this
}
link.waitForIt().click()
loginForm.waitForIt(10).guestButton.waitForIt().click()

_29
—
// Kotlin
...
return this
}

_30
—
// Kotlin
...
return this
}

_31
—
// Kotlin
...
return this
}

_32
—

• Java (Lombok https://projectlombok.org/)
• Groovy (Extension Modules)
_33
2. Extension functions: Java & Groovy
—

// Java
public class Credentials {
private final String username;
private final String password;
}
_34
3. Problem: small classes are not small
—

// Java
public Credentials(String username, String password) {
this.username = username;
this.password = password;
}
}
_35
—

// Java
}
public String getUsername() { return username; }
public String getPassword() { return password; }
}
_36
—

// Java
}
@Override
public String toString() {
return username + '/' + password;
}
}
_37
—

// 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);
}
}
_38
—

// 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);
}
}
_39
3. Problem: 27 lines
—

_40
3. griddynamics/jagger https://git.io/v9035
—

_41
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

• Java (Lombok https://projectlombok.org/)
• Groovy (@groovy.transform.Canonical)
_42
3. Data classes: Java & Groovy
—

// Java
driver.findElement("button").click();
_43
4. Problem: steps in Allure report
—

// Java
@Step("Click the button")
public void clickButton() {
}
clickButton();
_44
4. Problem: steps in Allure report
—

// Java 8
@Step("{0}")
public void step(String title, Runnable code) {
code.run();
}
step("Click the button", () -> {
});
_45
4. Solution: steps in Allure report
—

// Kotlin
@Step("{0}")
fun step(title: String, code: () -> Any) = code()
step("Click the button") {
driver.findElement("button").click()
}
_46
4. Solution: steps in Allure report
—

// Java 8
step("Click the button", () -> {
// your code here
});
// Kotlin
step("Click the button") {
// your code here
}
_47
4. Solution: just compare
—

• Java 7
• Java 8
• Groovy
_48
4. Steps in Allure report: Java & Groovy
—

// Java
URLDecoder.decode(param, "UTF-8");
_49
5. Problem: checked exceptions
—

// Java: String to md5
try {
...
} catch (NoSuchAlgorithmException ex) {
throw new RuntimeException(
"Unable apply MD5 algorithm for password hashing: ", ex);
} catch (UnsupportedEncodingException unsEx) {
throw new RuntimeException(
"Unable apply UTF-8 encoding for password string: ", unsEx);
}
_50
5. reportportal/service-api https://git.io/v9RF5
—

// Java
try {
screenshotUrl = new URL(screenshotUrl).toExternalForm();
} catch (MalformedURLException ignore) { }
_51
5. codeborne/selenide https://git.io/v9Rbe
—

// Java
try {
screenshotUrl = new URL(screenshotUrl).toExternalForm();
} catch (MalformedURLException ignore) { }
// Kotlin
screenshotUrl = URL(screenshotUrl).toExternalForm();
_52
5. Solution: no checked exceptions
—

• Java
• Groovy
_53
5. Checked exceptions: Java & Groovy
—

// Java
Object errors
= executeJavaScript("return window._selenide_jsErrors");
if (errors instanceof List) {
return errorsFromList((List<Object>) errors);
}
_54
6. Problem: unchecked cast https://git.io/v9Ek1
—

// Java
Object errors
return errorsFromList((List<Object>) errors);
}
_55
—

// Java
Object errors
return errorsFromList(((List<?>) errors)
.stream()
.filter(Object.class::isInstance)
.map(Object.class::cast)
.collect(toList())
);
}
_56
—

// Kotlin
val errors
if (errors is List<*>) {
return errorsFromList(errors.filterIsInstance<Object>())
}
_57
6. Solution: Kotlin smart cast
—

// Kotlin
val errors
if (errors is List<*>) {
return errorsFromList(errors.filterIsInstance<Object>())
}
_58
6. Solution: Kotlin smart cast
—

• Java
• Groovy
_59
6. Unchecked cast: Java & Groovy
—

_60
7. Problem:
— Java is verbose

// Java
actualText.equals(expectedText)
// Kotlin
actualText == expectedText
_61
7. Solution: Kotlin syntactic sugar
—

// 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}"
_62
7. Solution: String templates
—

// Java
for (int i = 0; i <= 10; i += 2)
// Kotlin
for (i in 0..10 step 2)
_63
7. Solution: ranges
—

// Java
!list.isEmpty()
// Kotlin
list.isNotEmpty()
_64
7. Solution: Kotlin rich standard library
—

• Java
• Groovy
_65
7. Verbosity: Java & Groovy
—

var username: String
username = null // compilation error
_67
8. Solution: Null safety
—

var username: String
username = null // compilation error
var username: String?
username = null // ok
_68
8. Null safety
—

var username: String // non-nullable String
username = null
var username: String? // nullable String
username = null
_69
8. Null safety
—

var username: String? = "Vasya"
var count = username.length // compilation error
_70
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
_71
8. Null safety: safe call
—

// Java
username != null ? username : "Guest"
_72
8. Null safety: Elvis operator
—

// Java
username != null ? username : "Guest"
// Kotlin
username ?: "Guest"
var images = findAllImagesOnPage()
?: throw AssertionError("No images!")
_73
8. Null safety: Elvis operator
—
?:

• Null safety: Java (Optional<T> in Java8), Groovy
• Safe call: Java, Groovy
• Elvis operator: Java, Groovy
_74
8. Null safety: Java & Groovy
—

_75
1 2 3 4 5 6 7 8
Java 7 − − − − − − − −
Java 8 ± − − + − − − −
Groovy + ± + + + − + −
Kotlin + + + + + + + +
Java vs Groovy vs Kotlin
—

• Not statically typed: runtime bugs
• Not statically typed: performance
• Not statically typed: IDE support
• No null safety
_76
Why not Groovy?
—

• Demo
_77
—

Kotlin ~ Java
—
// Kotlin
var counter: Int = 0
// Java
private int counter = 0;
public final int getCounter() {
return counter;
}
public final void setCounter(int newCounter) {
counter = newCounter;
}
_78

1. JUnit 4
—
@Before fun `start browser`() { ... }
@Test fun `test name`() { ... }
@Ignore("ISSUE-9000")
@Test fun `ignored test`() { ... }
@After fun `quit browser`() { ... }
_79

1. JUnit 4: @Rule
—
_81
// Kotlin
@Rule val tempFolder = TemporaryFolder()

1. JUnit 4: @Rule
—
_82
// Kotlin
org.junit.internal.runners.rules.ValidationError: The @Rule
'tempFolder' must be public.

1. JUnit 4: @Rule
—
_83
// Kotlin
// Java
@Rule
private final TemporaryFolder tempFolder = new TemporaryFolder();
public final TemporaryFolder getTempFolder() {
return tempFolder;
}

1. JUnit 4: @Rule solution #1
—
_84
// Kotlin
@JvmField @Rule val tempFolder = TemporaryFolder()
// Java
@Rule
public final TemporaryFolder tempFolder = new TemporaryFolder();

1. JUnit 4: @Rule solution #2
—
_85
// Kotlin
@get:Rule val tempFolder = TemporaryFolder()
// Java
private final TemporaryFolder tempFolder = new TemporaryFolder();
@Rule
public final TemporaryFolder getTempFolder() {
return tempFolder;
}

1. JUnit 4: @Parameters
—
_86
// Kotlin
@RunWith(Parameterized::class)
class ParameterizedTest {
@Parameters(name = "{0}")
fun data(): Collection<Array<String>> = asList(
arrayOf("firefox User-Agent"),
arrayOf("chrome User-Agent")
)
@Parameter lateinit var userAgent: String
}

—
_87
// Kotlin
)
}
java.lang.Exception: No public static parameters method on class
com.jetbrains.ParameterizedTest

Companion object
—
// Kotlin
class MyClass {
companion object {
fun looksLikeStatic() { ... }
}
}
MyClass.looksLikeStatic()
_88

—
_89
// Kotlin
companion object {
)
}
}

—
_90
// Kotlin
companion object {
)
}
}
java.lang.Exception: No public static parameters method on class
com.jetbrains.ParameterizedTest

1. JUnit 4: @Parameters solution
—
_91
// Kotlin
companion object {
@Parameters(name = "{0}") @JvmStatic
)
}
}

—
_92
// Java
@RunWith(Parameterized.class)
public final static class Companion {
public Collection<String[]> data() {
return asList(...);
}
}
public final static Companion Companion = new Companion();
public final static Collection<String[]> data() {
return Companion.data();
}
}

—
_93
// Java
return asList(...);
}
}
}
}

—
_94
// Java
return asList(...);
}
}
}
}

—
_95
// Java
return asList(...);
}
}
}
}

2. HtmlElements 1.*: element
—
_96
@FindBy(css = "form[name='LoginForm']")
class LoginForm : HtmlElement() {
@FindBy(css = "#username")
lateinit var usernameInput: HtmlElement
@FindBy(css = "#password")
lateinit var passwordInput: HtmlElement
@FindBy(xpath = ".//button")
lateinit var loginButton: HtmlElement
fun login(username: String, password: String) {
usernameInput.sendKeys(username)
passwordInput.sendKeys(password)
loginButton.click()
}
}

2. HtmlElements 1.*: page object
—
_97
class Page(val driver: WebDriver) {
init {
PageFactory.initElements(
HtmlElementDecorator(
HtmlElementLocatorFactory(driver)), this)
}
lateinit var loginForm: LoginForm
@FindBy(css = ".dashboard-buttons_add")
lateinit var addWidgetButton: HtmlElement
}

2. HtmlElements 1.*: collection of elements
—
_99
// Kotlin
@FindBy(css = "a")
lateinit var links: List<HtmlElement>
...
links.forEach { ... }

—
_100
// Kotlin
@FindBy(css = "a")
...
links.forEach { ... }
kotlin.UninitializedPropertyAccessException

—
_101
// Kotlin
@FindBy(css = "a")
java.util.List<? extends
ru.yandex.qatools.htmlelements.element.HtmlElement>

—
_102
// Kotlin
@FindBy(css = "a")
lateinit var links: List<@JvmSuppressWildcards HtmlElement>
java.util.List<ru.yandex.qatools.htmlelements.element.HtmlElement>
• https://kotlinlang.org/docs/reference/java-to-kotlin-interop.html#variant-generics

3. Allure
—
_103
// Kotlin
@Title("This is title")
@Description("This is description")
@Test fun test() { ... }
@Step("Change Home URL to {0}")
fun changeHomeURL(homeURL: String) { ... }
@Attachment(value = "{0}", type = "text/plain")
fun attachText(name: String = "text", text: String?) = text

3. Allure: org.aspectj:aspectjweaver:1.8.10
—
_105
// Kotlin
links.forEach {
println(it.text)
}

—
_106
// Kotlin
links.forEach {
println(it.text)
}
java.lang.ClassFormatError: Invalid index 6 in
LocalVariableTable

—
_107
// Kotlin
links.forEach {
println(it.text)
}
java.lang.ClassFormatError: Invalid index 6 in
LocalVariableTable
• https://bugs.eclipse.org/bugs/show_bug.cgi?id=500796

4. Selenide: $ is reserved
—
_108
// Kotlin
import com.codeborne.selenide.Selenide.$
Error: Kotlin: Qualified name must be a '.'-separated
identifier list

4. Selenide: $ is reserved
—
_109
// Kotlin
import com.codeborne.selenide.Selenide.`$`
import com.codeborne.selenide.Selenide.`$$`
...
`$`("a")
`$$`("a")

5. Selenium WebDriver
—
_111
// Kotlin
val driver = RemoteWebDriver(
URL("http://grid.company.com:4444/wd/hub"),
DesiredCapabilities.chrome())
driver.manage().window().size = Dimension(800, 600)
driver.get("https://heisenbug-piter.ru")
val link = driver.findElement(By.cssSelector("a.navbar-
brand"))
val text = link.text
val clazz = link.getAttribute("class")
Actions(driver).moveToElement(link).perform()
(driver as TakesScreenshot).getScreenshotAs(OutputType.BYTES)
driver.quit()

6. REST Assured
—
_113
// Kotlin
fun createIssue(issue: Issue): Issue = given()
.baseUri("http://host:8080")
.header("Authorization", "*token*")
.contentType("application/json")
.accept("application/json")
.queryParams(mapOf("fields" to
"id,project(id,shortName),numberInProject"))
.with().body(issue)
.post("/api/issues")
.`as`(Issue::class.java)

• Demo
_114
—

_115
Example web tests project in Kotlin
—
gradle-docker-plugin

_116
—
JUnit, Html Elements

_117
—
JUnit, Html Elements

_118
• Kotlin + { Gradle, JUnit, Selenium, Html Elements, Allure } = OK
https://github.com/leonsabr/web-tests-in-kotlin-demo
—

_119
• Kotlin + { Gradle, JUnit, Selenium, Html Elements, Allure }
• Java interoperability
—

_120
—

_121
java kotlin ∆
main 675 434 35,7%
test 89 84 5,6%
total 764 518 32,2%
• Kotlin + { Gradle, JUnit, Selenium, Html Elements, Allure }
• Java interoperability
• Conciseness (lines of code)
—

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

Java → kotlin: Tests Made Simple

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