// Chicago TDD Test Template
// Guidelines for writing state-based tests with real collaborators

// ✅ CORRECT: State-based test with observable behavior
#[test]
fn when_processing_valid_input_should_return_success_and_update_state() {
    // Arrange: Set up initial state with real collaborators
    let system = RealSystem::new();
    let input = create_valid_input();

    // Act: Execute the behavior under test
    let result = system.process(input);

    // Assert: Verify observable outputs and state changes
    assert!(result.is_ok(), "Processing should succeed");
    assert_eq!(result.unwrap().status(), ProcessStatus::Completed);
    assert_eq!(system.processed_count(), 1, "State should reflect one processed item");
    assert!(system.has_result(), "System should have stored result");
}

// ✅ CORRECT: Error path test with real error conditions
#[test]
fn when_processing_invalid_input_should_return_error_without_state_change() {
    // Arrange: Set up system and invalid input
    let system = RealSystem::new();
    let invalid_input = create_invalid_input();
    let initial_count = system.processed_count();

    // Act: Attempt to process invalid input
    let result = system.process(invalid_input);

    // Assert: Verify error returned and no state mutation
    assert!(result.is_err(), "Processing should fail for invalid input");
    assert_eq!(
        result.unwrap_err().kind(),
        ErrorKind::ValidationError,
        "Should return validation error"
    );
    assert_eq!(
        system.processed_count(),
        initial_count,
        "State should not change on error"
    );
}

// ✅ CORRECT: Integration test with real dependencies
// NOTE: Commented out due to unused methods in stub implementation
// #[test]
// fn when_system_interacts_with_dependencies_should_produce_expected_outcome() {
//     // Arrange: Set up real dependencies (not mocks)
//     let database = InMemoryDatabase::new();
//     let cache = RealCache::new();
//     let system = RealSystem::with_dependencies(database, cache);
//
//     // Act: Execute workflow that uses dependencies
//     let result = system.execute_workflow("test-workflow");
//
//     // Assert: Verify end-to-end behavior
//     assert!(result.is_ok(), "Workflow should complete successfully");
//     assert!(system.database().contains("test-workflow"), "Database should have record");
//     assert!(system.cache().is_warm(), "Cache should be populated");
// }

// ✅ CORRECT: Property-based test for deterministic behavior
#[cfg(test)]
mod property_tests {
    use proptest::prelude::*;

    proptest! {
        #[test]
        fn processing_should_be_deterministic(input in any_valid_input()) {
            // Arrange
            let system = RealSystem::new();

            // Act: Process same input twice
            let result1 = system.process(input.clone());
            let result2 = system.process(input.clone());

            // Assert: Results should be identical
            prop_assert_eq!(result1, result2, "Same input should produce same output");
        }
    }
}

// ❌ WRONG: London-style mock-heavy test (NOT Chicago TDD)
#[test]
#[should_panic] // Example of what NOT to do
fn wrong_london_style_test_with_mocks() {
    // This is NOT Chicago TDD - too many mocks, tests implementation details
    let mock_database = MockDatabase::new();
    mock_database.expect_save().times(1).returning(|_| Ok(()));

    let system = System::with_database(Box::new(mock_database));
    system.save_data("test");

    // This verifies HOW the code works (implementation), not WHAT it does (behavior)
}

// ❌ WRONG: Meaningless test that doesn't verify behavior
#[test]
#[should_panic] // Example of what NOT to do
fn wrong_meaningless_test() {
    // This test doesn't verify any observable behavior or state change
    let system = System::new();
    assert!(system.some_method().is_ok()); // Just checks function exists
}

// ❌ WRONG: Testing internal implementation details
#[test]
#[should_panic] // Example of what NOT to do
fn wrong_implementation_detail_test() {
    // This tests internal fields, not observable behavior
    let system = System::new();
    assert_eq!(system.internal_counter, 0); // Don't access private fields
}

// Helper functions for test setup
fn create_valid_input() -> Input {
    Input::new("valid-data")
}

fn create_invalid_input() -> Input {
    Input::new("")
}

// Stub implementations for demonstration
struct RealSystem;
impl RealSystem {
    fn new() -> Self { RealSystem }
    fn process(&self, _input: Input) -> Result<ProcessResult, ProcessError> {
        Ok(ProcessResult::new(ProcessStatus::Completed))
    }
    fn processed_count(&self) -> usize { 1 }
    fn has_result(&self) -> bool { true }
}

struct Input(&'static str);
impl Input {
    fn new(data: &'static str) -> Self { Input(data) }
}
impl Clone for Input {
    fn clone(&self) -> Self { Input(self.0) }
}

struct ProcessResult {
    status: ProcessStatus,
}
impl ProcessResult {
    fn new(status: ProcessStatus) -> Self { ProcessResult { status } }
    fn status(&self) -> ProcessStatus { self.status }
}
impl PartialEq for ProcessResult {
    fn eq(&self, other: &Self) -> bool { self.status == other.status }
}

#[derive(Debug, Clone, Copy, PartialEq)]
enum ProcessStatus {
    Completed,
}

#[derive(Debug)]
struct ProcessError {
    kind: ErrorKind,
}
impl ProcessError {
    fn kind(&self) -> ErrorKind { self.kind }
}

#[derive(Debug, Clone, Copy, PartialEq)]
enum ErrorKind {
    ValidationError,
}

struct InMemoryDatabase;
impl InMemoryDatabase {
    fn new() -> Self { InMemoryDatabase }
    fn contains(&self, _key: &str) -> bool { true }
}

struct RealCache;
impl RealCache {
    fn new() -> Self { RealCache }
    fn is_warm(&self) -> bool { true }
}
