Pfthb

I am trying to write some UnitTests for my native mobile applications, but have ran into a roadblock in my Android Tests. Specifically, I am struggling to find an example of Kotlin's version of Swift's Expectations/Promises..

I've found examples of Kotlin Promises, but they seem to be way more complicated than needed...

For example, here is a test for the login API function in my iOS project:

func testLogin() 

 /// Prepare for login
 if CURRENT_USER != nil 
 logout()
 

 /// Login
 let promise = expectation(description: "User is logged in.")

 // 1. Given
 var isSuccess: Bool = false

 // 2. When
 User.login(username: maleUsername, password: malePassword, success: 
 isSuccess = true
 promise.fulfill()
 ) (_, agreeToTerms) in
 XCTFail()
 
 wait(for: [promise], timeout: maxTimeOut)

 // 3. Then
 XCTAssertNotNil(CURRENT_USER)
 XCTAssertTrue(isSuccess)

 /// Logout
 logout()

This is pretty simple to me. I have an asynchronous method login that has two possible completion blocks: success and failure; and I need to wait for one of them to complete before evaluating. To do this, I create a promise before the call, then I fulfill the promise in the two completion blocks, and I wait for the promise to fulfill before running my assertions.

Now in Kotlin, I have a similar test:

private val loginFragment = LoginFragment()

@Test
fun loginTest() 

 val username = ""
 val password = ""

 // TODO: Create Promise

 loginFragment.loginViewModel
 .login(username, password)
 .observe(loginFragment, Observer 
 loginFragment.activity?.onResult(it?.result,

 onSuccess = 
 // TODO: Fill Promise
 ,
 onValidationError = 
 // TODO: Fail Test
 )
 )

 // TODO: Assertions

But I can't find an equivalent of swift's promises..

Does one exist in Kotlin? If not, how would I implement a version of my Swift's testLogin method in Kotlin?

You can use Kotlin coroutines, for example:

@Test
fun loginTest() 
 val result = runBlocking 
 val loginResult = login() 
 loginResult
 
 if (result == "Success") 
 // do your work when Success
 else 
 // do your work when Error
 

suspend fun login(): String = suspendCoroutine continuation ->
 val username = ""
 val password = ""
 loginFragment.loginViewModel
 .login(username, password)
 .observe(loginFragment, Observer 
 loginFragment.activity?.onResult(it?.result,

 onSuccess = 
 continuation.resume("Success")
 ,
 onValidationError = 
 continuation.resume("Error") // take a look for other methods, e.g. resumeWithException(exception)

 )
 ) 

To use coroutines you need to add next lines to app's build.gradle file dependencies:

final KOTLIN_COROUTINES_VERSION = '1.0.1'
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$KOTLIN_COROUTINES_VERSION"

Hope it will help.