Test Utilities

/**
 * Asserts that the given function block returns the expected value.
 * @param expected The value that the block should return
 * @param block The function to execute and validate
 * @throws AssertionError if the block returns a different value
 */
fun <T> expect(expected: T, block: () -> T)

/**
 * Asserts that the given function block returns the expected value with a custom message.
 * @param expected The value that the block should return
 * @param message Optional message to show if assertion fails
 * @param block The function to execute and validate
 * @throws AssertionError if the block returns a different value
 */
fun <T> expect(expected: T, message: String?, block: () -> T)

import kotlin.test.expect

@Test
fun testExpectFunction() {
    // Basic expectation testing
    expect(10) { 5 + 5 }
    expect("hello") { "hel" + "lo" }
    expect(true) { 10 > 5 }
    
    // Complex function testing
    expect(42) { 
        val calculator = Calculator()
        calculator.add(40, 2)
    }
    
    // With custom messages
    expect(100, "Score calculation should return 100") {
        gameLogic.calculateFinalScore()
    }
    
    // Testing object methods
    val user = User("Alice", 25)
    expect("Alice") { user.getName() }
    expect(25) { user.getAge() }
    
    // Collection operations
    expect(3) { listOf(1, 2, 3).size }
    expect("HELLO") { "hello".uppercase() }
}

@Test
fun testComplexExpectations() {
    // Testing with side effects
    val counter = Counter()
    expect(1) { counter.increment() }
    expect(2) { counter.increment() }
    expect(0) { counter.reset(); counter.getValue() }
    
    // API call testing
    val apiClient = TestApiClient()
    expect(200) { apiClient.getStatus("/health").statusCode }
    expect("OK") { apiClient.getStatus("/health").message }
    
    // Conditional logic testing
    expect("adult") {
        val person = Person(age = 25)
        if (person.age >= 18) "adult" else "minor"
    }
}

/**
 * Marks a test as failed with the specified message.
 * This function never returns normally - it always throws.
 * @param message Optional failure message
 * @return Nothing (this function never returns)
 * @throws AssertionError always
 */
fun fail(message: String? = null): Nothing

/**
 * Marks a test as failed with the specified message and underlying cause.
 * This function never returns normally - it always throws.
 * @param message Optional failure message
 * @param cause Optional underlying cause of the failure
 * @return Nothing (this function never returns)
 * @throws AssertionError always
 * @since Kotlin 1.4
 */
fun fail(message: String? = null, cause: Throwable? = null): Nothing

import kotlin.test.fail

@Test
fun testFailFunction() {
    val condition = checkSomeCondition()
    
    if (!condition) {
        fail("Expected condition to be true but it was false")
    }
    
    // Unreachable code after fail()
    println("This will never execute")
}

@Test
fun testConditionalFailure() {
    val result = performComplexOperation()
    
    when (result.status) {
        Status.SUCCESS -> {
            // Test passes, continue validation
            assertTrue(result.data.isNotEmpty())
        }
        Status.ERROR -> {
            fail("Operation failed with error: ${result.errorMessage}")
        }
        Status.UNKNOWN -> {
            fail("Operation returned unknown status")
        }
    }
}

@Test
fun testFailWithCause() {
    try {
        val service = ExternalService()
        service.performOperation()
    } catch (e: ServiceException) {
        fail("Service operation should not throw exception", e)
    } catch (e: Exception) {
        fail("Unexpected exception occurred", e)
    }
}

@Test
fun testValidationFailure() {
    val data = loadTestData()
    
    // Explicit validation with meaningful failure messages
    if (data.isEmpty()) {
        fail("Test data should not be empty")
    }
    
    if (data.size < 10) {
        fail("Test data should contain at least 10 items, but got ${data.size}")
    }
    
    // Continue with normal test logic
    assertTrue(data.all { it.isValid() })
}

/**
 * Takes a block of test code and doesn't execute it.
 * Used to mark tests that are not yet implemented or should be skipped.
 * This is an expect declaration that has platform-specific implementations.
 * @param block The test code that should not be executed
 */
fun todo(block: () -> Unit)

import kotlin.test.todo
import kotlin.test.Test

class UserServiceTest {
    
    @Test
    fun testCreateUser() {
        // Implemented test
        val service = UserService()
        val user = service.createUser("Alice", "alice@example.com")
        assertEquals("Alice", user.name)
    }
    
    @Test
    fun testUpdateUser() {
        todo {
            // This test is not yet implemented
            // The block won't execute but the test will be reported as TODO
            val service = UserService()
            val user = service.updateUser(1, "Bob", "bob@example.com")
            assertEquals("Bob", user.name)
        }
    }
    
    @Test
    fun testDeleteUser() {
        todo {
            // Placeholder for future test implementation
            val service = UserService()
            service.deleteUser(1)
            assertNull(service.findUser(1))
        }
    }
    
    @Test
    fun testComplexUserOperation() {
        todo {
            // This test requires complex setup that's not ready yet
            val service = UserService()
            val database = TestDatabase.setup()
            val cache = TestCache.setup()
            
            // Complex test logic here...
            val result = service.performComplexOperation()
            assertTrue(result.isSuccess)
        }
    }
}

class IntegrationTest {
    
    @Test
    fun testBasicIntegration() {
        // Working integration test
        val client = ApiClient()
        val response = client.ping()
        assertEquals(200, response.status)
    }
    
    @Test
    fun testAdvancedIntegration() {
        todo {
            // This integration test needs external service setup
            val client = ApiClient()
            val externalService = ExternalService.connect()
            
            val result = client.performIntegration(externalService)
            assertTrue(result.isSuccess)
        }
    }
}

// Use expect for concise testing
expect(5) { list.size }
expect("result") { processor.process(input) }

// Use assertEquals for explicit comparison
val actual = processor.process(input)
assertEquals("result", actual)

@Test
fun testCustomValidation() {
    val result = complexOperation()
    
    // Custom business logic validation
    if (!result.isValid() || result.score < 0) {
        fail("Result failed business validation: $result")
    }
    
    // Additional standard assertions
    assertTrue(result.isComplete())
}

class NewFeatureTest {
    
    @Test
    fun testImplementedPart() {
        // Already working
        assertTrue(newFeature.basicFunctionality())
    }
    
    @Test
    fun testAdvancedPart() {
        todo {
            // Will implement after basic part is stable
            assertTrue(newFeature.advancedFunctionality())
        }
    }
}

// This will throw: AssertionError: Expected <5>, actual <3>.
expect(5) { listOf(1, 2, 3).size }

// This will throw: AssertionError: Custom validation failed
fail("Custom validation failed")