Exception and Failure Testing

/**
 * Marks a test as having failed if this point in the execution path is reached
 * @param message - Optional failure message
 * @return Nothing (function never returns)
 */
fun fail(message: String? = null): Nothing

/**
 * Marks a test as having failed with an optional message and cause exception
 * @param message - Optional failure message
 * @param cause - Optional exception that caused the failure
 * @return Nothing (function never returns)
 */
fun fail(message: String? = null, cause: Throwable? = null): Nothing

import kotlin.test.*

@Test
fun testConditionalFailure() {
    val result = performCriticalOperation()
    
    when (result.status) {
        Status.SUCCESS -> {
            // Test passes, continue validation
            assertTrue(result.data.isNotEmpty())
        }
        Status.RECOVERABLE_ERROR -> {
            // Expected failure scenario
            assertTrue(result.canRetry)
        }
        Status.FATAL_ERROR -> {
            fail("Critical operation failed: ${result.errorMessage}")
        }
        else -> {
            fail("Unexpected status: ${result.status}")
        }
    }
}

@Test
fun testWithCause() {
    try {
        val connection = establishConnection()
        if (connection == null) {
            fail("Failed to establish connection")
        }
    } catch (e: NetworkException) {
        fail("Network error during connection", e)
    }
}

/**
 * Asserts that given function block fails by throwing an exception
 * @param block - Code block that should throw an exception
 * @return The exception that was thrown
 */
inline fun assertFails(block: () -> Unit): Throwable

/**
 * Asserts that given function block fails by throwing an exception
 * @param message - Optional message used as prefix for failure message
 * @param block - Code block that should throw an exception
 * @return The exception that was thrown
 */
inline fun assertFails(message: String?, block: () -> Unit): Throwable

@Test
fun testExceptionHandling() {
    // Test that division by zero throws
    val exception = assertFails {
        val result = 10 / 0
    }
    assertTrue(exception is ArithmeticException)
    
    // Test with custom message
    val parseException = assertFails("Should fail to parse invalid number") {
        "not-a-number".toInt()
    }
    assertTrue(parseException is NumberFormatException)
    
    // Inspect exception details
    val validationException = assertFails {
        validateEmail("invalid-email")
    }
    assertContains(validationException.message ?: "", "email")
}

@Test
fun testApiErrorHandling() {
    val client = ApiClient()
    
    // Test unauthorized access
    val authException = assertFails("Should fail with invalid token") {
        client.makeRequest("/protected", token = "invalid")
    }
    
    // Verify we can inspect the returned exception
    assertTrue(authException.message?.contains("unauthorized") == true)
}

/**
 * Asserts that a block fails with a specific exception of type T
 * @param message - Optional message used as prefix for failure message
 * @param block - Code block that should throw exception of type T
 * @return Exception of the expected type T
 */
inline fun <reified T : Throwable> assertFailsWith(message: String? = null, block: () -> Unit): T

/**
 * Asserts that a block fails with a specific exception of the given class
 * @param exceptionClass - Expected exception class
 * @param block - Code block that should throw the exception
 * @return Exception of the expected type T
 */
inline fun <T : Throwable> assertFailsWith(exceptionClass: KClass<T>, block: () -> Unit): T

/**
 * Asserts that a block fails with a specific exception of the given class
 * @param exceptionClass - Expected exception class
 * @param message - Optional message used as prefix for failure message  
 * @param block - Code block that should throw the exception
 * @return Exception of the expected type T
 */
inline fun <T : Throwable> assertFailsWith(exceptionClass: KClass<T>, message: String?, block: () -> Unit): T

@Test
fun testSpecificExceptions() {
    // Test specific exception type with reified generic
    val illegalArg = assertFailsWith<IllegalArgumentException> {
        validateAge(-5)
    }
    assertEquals("Age cannot be negative", illegalArg.message)
    
    // Test with custom message
    val nullPointer = assertFailsWith<NullPointerException>("Should throw NPE for null input") {
        processData(null)
    }
    
    // Test with KClass parameter
    val ioException = assertFailsWith(IOException::class) {
        readFile("nonexistent.txt")
    }
    assertContains(ioException.message ?: "", "nonexistent.txt")
}

@Test
fun testCustomExceptions() {
    class ValidationException(message: String) : Exception(message)
    
    val validationError = assertFailsWith<ValidationException> {
        validateUserInput(UserInput(name = "", email = "invalid"))
    }
    
    assertContains(validationError.message ?: "", "name")
    assertContains(validationError.message ?: "", "email")
}

@Test
fun testExceptionHierarchy() {
    // Test that we catch the specific subtype
    val specificException = assertFailsWith<FileNotFoundException> {
        openFile("missing.txt")
    }
    
    // FileNotFoundException is also an IOException
    assertTrue(specificException is IOException)
}

/**
 * Asserts that given function block returns the given expected value
 * @param expected - Expected return value
 * @param block - Function that should return the expected value
 */
inline fun <T> expect(expected: T, block: () -> T)

/**
 * Asserts that given function block returns the given expected value with custom message
 * @param expected - Expected return value  
 * @param message - Optional custom failure message
 * @param block - Function that should return the expected value
 */
inline fun <T> expect(expected: T, message: String?, block: () -> T)

@Test
fun testExpectedValues() {
    // Simple calculation
    expect(25) { 5 * 5 }
    
    // String operations
    expect("HELLO") { "hello".uppercase() }
    
    // With custom message
    expect(true, "User should be authenticated") { 
        authenticateUser("admin", "password123") 
    }
    
    // Complex operations
    expect(listOf(2, 4, 6)) {
        listOf(1, 2, 3).map { it * 2 }
    }
}

@Test
fun testFunctionResults() {
    // Test pure functions
    expect(42) { fibonacci(9) }  // 9th Fibonacci number
    
    // Test with side effects
    val cache = mutableMapOf<String, Int>()
    expect(5) {
        cache.computeIfAbsent("key") { 5 }
    }
    
    // Verify side effect occurred
    assertTrue(cache.containsKey("key"))
}

@Test
fun testExceptionChaining() {
    class DatabaseException(message: String, cause: Throwable) : Exception(message, cause)
    class ServiceException(message: String, cause: Throwable) : Exception(message, cause)
    
    val serviceException = assertFailsWith<ServiceException> {
        try {
            // Simulate database failure
            throw SQLException("Connection timeout")
        } catch (e: SQLException) {
            throw DatabaseException("Database operation failed", e)
        } catch (e: DatabaseException) {
            throw ServiceException("Service unavailable", e)
        }
    }
    
    // Verify exception chain
    assertNotNull(serviceException.cause)
    assertTrue(serviceException.cause is DatabaseException)
    
    val dbException = serviceException.cause as DatabaseException
    assertNotNull(dbException.cause)
    assertTrue(dbException.cause is SQLException)
    
    val sqlException = dbException.cause as SQLException
    assertEquals("Connection timeout", sqlException.message)
}

@Test
fun testResourceCleanup() {
    class Resource : AutoCloseable {
        var closed = false
        override fun close() { closed = true }
    }
    
    val resource = Resource()
    
    // Test that exception doesn't prevent cleanup
    assertFailsWith<IllegalStateException> {
        try {
            resource.use {
                throw IllegalStateException("Simulated error")
            }
        } finally {
            assertTrue(resource.closed, "Resource should be closed even after exception")
        }
    }
}

@Test
fun testInputValidation() {
    data class User(val name: String, val email: String, val age: Int)
    
    fun validateUser(user: User) {
        require(user.name.isNotBlank()) { "Name cannot be blank" }
        require(user.email.contains("@")) { "Invalid email format" }
        require(user.age >= 0) { "Age cannot be negative" }
    }
    
    // Test each validation rule
    assertFailsWith<IllegalArgumentException>("Should reject blank name") {
        validateUser(User("", "test@example.com", 25))
    }
    
    assertFailsWith<IllegalArgumentException>("Should reject invalid email") {
        validateUser(User("John", "invalid-email", 25))
    }
    
    assertFailsWith<IllegalArgumentException>("Should reject negative age") {
        validateUser(User("John", "john@example.com", -1))
    }
    
    // Test valid input doesn't throw
    assertDoesNotThrow {
        validateUser(User("John", "john@example.com", 25))
    }
}

// Helper function for readability
inline fun assertDoesNotThrow(block: () -> Unit) {
    try {
        block()
    } catch (e: Exception) {
        fail("Expected no exception, but got: ${e::class.simpleName}: ${e.message}")
    }
}

@Test
fun testTimeoutBehavior() {
    // Test that long-running operation times out
    val timeoutException = assertFailsWith<TimeoutException> {
        runWithTimeout(100) { // 100ms timeout
            Thread.sleep(1000) // Sleep for 1 second
        }
    }
    
    assertContains(timeoutException.message ?: "", "timeout")
}

@Test
fun testAsyncExceptions() {
    val future = CompletableFuture<String>()
    
    // Complete with exception
    future.completeExceptionally(RuntimeException("Async failure"))
    
    val executionException = assertFailsWith<ExecutionException> {
        future.get()
    }
    
    assertTrue(executionException.cause is RuntimeException)
    assertEquals("Async failure", executionException.cause?.message)
}

@Test  
fun testStateMachine() {
    enum class State { CREATED, STARTED, STOPPED, DISPOSED }
    
    class StateMachine {
        private var state = State.CREATED
        
        fun start() {
            require(state == State.CREATED) { "Can only start from CREATED state" }
            state = State.STARTED
        }
        
        fun stop() {
            require(state == State.STARTED) { "Can only stop from STARTED state" }  
            state = State.STOPPED
        }
        
        fun dispose() {
            require(state == State.STOPPED) { "Can only dispose from STOPPED state" }
            state = State.DISPOSED
        }
    }
    
    val machine = StateMachine()
    
    // Test invalid transitions
    assertFailsWith<IllegalArgumentException>("Should not stop before starting") {
        machine.stop()
    }
    
    assertFailsWith<IllegalArgumentException>("Should not dispose before stopping") {
        machine.dispose()
    }
    
    // Test valid sequence
    machine.start()
    machine.stop()
    machine.dispose()
    
    // Test invalid transition after disposal
    assertFailsWith<IllegalArgumentException>("Should not restart after disposal") {
        machine.start()
    }
}

/**
 * Takes the given block of test code and doesn't execute it
 * This keeps the code under test referenced, but doesn't actually test it until implemented
 * @param block - Test code block to skip execution
 */
fun todo(block: () -> Unit)

import kotlin.test.*

@Test
fun testComplexFeature() {
    // Test implemented part
    val basicResult = performBasicOperation()
    assertEquals("expected", basicResult)
    
    // Skip unimplemented test but keep it in code
    todo {
        // This test code won't execute but stays in the codebase
        val advancedResult = performAdvancedOperation()
        assertEquals("advanced", advancedResult)
        assertNotNull(advancedResult.metadata)
    }
}

@Test
fun testTodoWithDescription() {
    // Test current implementation
    val service = createService()
    assertTrue(service.isReady())
    
    // TODO: Add comprehensive integration tests
    todo {
        // Integration test placeholder - won't run
        val integrationResult = service.performIntegration()
        assertTrue(integrationResult.success)
        assertContains(integrationResult.logs, "Integration completed")
    }
}

class IncrementalTestDevelopment {
    @Test
    fun testBasicFunctionality() {
        // Implemented test
        val calculator = Calculator()
        assertEquals(4, calculator.add(2, 2))
    }
    
    @Test
    fun testAdvancedFunctionality() {
        todo {
            // Placeholder for future advanced tests
            val calculator = Calculator()
            assertEquals(8.0, calculator.power(2.0, 3.0), 0.001)
            assertEquals(2.0, calculator.sqrt(4.0), 0.001)
        }
    }
}

/**
 * Represents a Kotlin class for type-safe exception assertions
 */
typealias KClass<T> = kotlin.reflect.KClass<T>