# GUT (Godot Unit Testing) - Setup & Usage Guide

## Overview

GUT is a unit testing framework for Godot that allows you to write and run automated tests for your GDScript code. It's already installed in your project at `addons/gut/`.

**Version:** 9.6.0  
**Author:** Butch Wesley  
**Documentation:** https://gut.readthedocs.io

## Quick Start

### 1. Enable GUT Plugin

1. Open your Godot project
2. Go to **Project → Project Settings → Plugins**
3. Find "Gut" and enable it
4. Restart the editor

### 2. Create Your First Test

Create a new GDScript file in a `tests/` folder:

```gdscript
# tests/test_example.gd
extends GutTest

func test_addition():
    assert_eq(2 + 2, 4, "2 + 2 should equal 4")

func test_string_comparison():
    assert_eq("hello", "hello", "Strings should match")
```

### 3. Run Tests

- **In Editor:** Go to **Tools → GUT → Run Tests**
- **From Command Line:** `godot --headless -s addons/gut/gut_cmdln.gd`

## GUT Test Structure

### Lifecycle Methods

```gdscript
extends GutTest

# Runs once before all tests in this script
func before_all():
    pass

# Runs before each test
func before_each():
    pass

# Runs after each test
func after_each():
    pass

# Runs once after all tests in this script
func after_all():
    pass

# Test methods must start with "test_"
func test_something():
    pass
```

### Test Naming Convention

- Test methods **must** start with `test_`
- Use descriptive names: `test_player_takes_damage()`, `test_invalid_input_rejected()`
- Each test should test ONE thing

## Common Assertions

### Equality Assertions

```gdscript
# Assert equal
assert_eq(actual, expected, "Optional message")
assert_eq(2 + 2, 4)

# Assert not equal
assert_ne(actual, expected, "Optional message")
assert_ne(1, 2)

# Assert true/false
assert_true(condition, "Optional message")
assert_false(condition, "Optional message")
```

### Type Assertions

```gdscript
# Assert is instance of type
assert_is(obj, Node, "Should be a Node")

# Assert has method
assert_has_method(obj, "method_name")

# Assert has property
assert_has_property(obj, "property_name")
```

### Collection Assertions

```gdscript
# Assert array contains value
assert_has(array, value, "Array should contain value")

# Assert array does not contain value
assert_does_not_have(array, value)

# Assert array is empty
assert_is_empty(array)

# Assert array is not empty
assert_is_not_empty(array)
```

### String Assertions

```gdscript
# Assert string contains substring
assert_string_contains(string, substring)

# Assert string starts with
assert_string_starts_with(string, prefix)

# Assert string ends with
assert_string_ends_with(string, suffix)
```

### Signal Assertions

```gdscript
# Watch a signal
watch_signals(object)

# Assert signal was emitted
assert_signal_emitted(object, "signal_name")

# Assert signal was emitted with arguments
assert_signal_emitted_with_arguments(object, "signal_name", [arg1, arg2])

# Assert signal was not emitted
assert_signal_not_emitted(object, "signal_name")
```

## Project Structure for Tests

Recommended folder structure:

```
tekton-enet/
├── addons/
│   └── gut/
├── scripts/
│   ├── player.gd
│   ├── enemy.gd
│   └── game_manager.gd
├── tests/
│   ├── test_player.gd
│   ├── test_enemy.gd
│   ├── test_game_manager.gd
│   └── unit/
│       ├── test_math_utils.gd
│       └── test_string_utils.gd
└── project.godot
```

## Example Test Files

### Testing a Simple Class

```gdscript
# tests/test_player.gd
extends GutTest

var player: Node

func before_each():
    # Create a fresh player instance for each test
    player = preload("res://scripts/player.gd").new()

func after_each():
    # Clean up
    if player:
        player.queue_free()

func test_player_starts_with_100_health():
    assert_eq(player.health, 100, "Player should start with 100 health")

func test_player_takes_damage():
    player.take_damage(25)
    assert_eq(player.health, 75, "Player health should be 75 after taking 25 damage")

func test_player_dies_at_zero_health():
    player.health = 0
    assert_true(player.is_dead(), "Player should be dead at 0 health")

func test_player_cannot_have_negative_health():
    player.take_damage(200)
    assert_true(player.health >= 0, "Player health should never be negative")
```

### Testing with Signals

```gdscript
# tests/test_game_manager.gd
extends GutTest

var game_manager: Node

func before_each():
    game_manager = preload("res://scripts/game_manager.gd").new()
    add_child(game_manager)

func after_each():
    game_manager.queue_free()

func test_game_start_emits_signal():
    watch_signals(game_manager)
    game_manager.start_game()
    assert_signal_emitted(game_manager, "game_started")

func test_game_over_emits_with_winner():
    watch_signals(game_manager)
    game_manager.end_game("Player1")
    assert_signal_emitted_with_arguments(game_manager, "game_ended", ["Player1"])
```

### Testing with Mocking/Stubbing

```gdscript
# tests/test_enemy.gd
extends GutTest

var enemy: Node

func before_each():
    enemy = preload("res://scripts/enemy.gd").new()

func test_enemy_calls_attack_on_player():
    # Create a mock player
    var mock_player = double(preload("res://scripts/player.gd"))
    
    # Have enemy attack the mock player
    enemy.attack(mock_player)
    
    # Verify the mock player's take_damage was called
    assert_called(mock_player, "take_damage")
```

## GUT Configuration

### gutconfig.json

Create `gutconfig.json` in your project root to configure GUT:

```json
{
  "dirs": ["res://tests"],
  "should_exit": true,
  "log_level": 1,
  "ignore_pause_before_teardown": false,
  "should_print_debug": false,
  "double_strategy": "FULL"
}
```

**Configuration Options:**
- `dirs`: Directories to search for test files
- `should_exit`: Exit after tests complete (useful for CI/CD)
- `log_level`: 0 (failures only), 1 (tests + failures), 2 (all asserts)
- `ignore_pause_before_teardown`: Ignore pause calls in batch mode
- `should_print_debug`: Print debug output
- `double_strategy`: "FULL" or "PARTIAL" for mocking

## Running Tests

### In Editor

1. **Tools → GUT → Run Tests** - Runs all tests
2. **Tools → GUT → Run Tests (with options)** - Configure before running
3. **Tools → GUT → Run a specific test** - Select a test file

### Command Line

```bash
# Run all tests
godot --headless -s addons/gut/gut_cmdln.gd

# Run specific test directory
godot --headless -s addons/gut/gut_cmdln.gd -d res://tests

# Run with specific log level
godot --headless -s addons/gut/gut_cmdln.gd -l 2

# Export results to JUnit XML (for CI/CD)
godot --headless -s addons/gut/gut_cmdln.gd -o results.xml
```

### CI/CD Integration

For GitHub Actions:

```yaml
- name: Run GUT Tests
  run: |
    godot --headless -s addons/gut/gut_cmdln.gd \
      -d res://tests \
      -o test-results.xml
```

## Best Practices

### 1. One Assertion Per Test (When Possible)

```gdscript
# GOOD - Each test tests one thing
func test_player_health_decreases():
    player.take_damage(10)
    assert_eq(player.health, 90)

func test_player_dies_at_zero():
    player.health = 0
    assert_true(player.is_dead())

# AVOID - Multiple assertions in one test
func test_player_damage():
    player.take_damage(10)
    assert_eq(player.health, 90)
    assert_false(player.is_dead())
    player.take_damage(100)
    assert_true(player.is_dead())
```

### 2. Use Descriptive Test Names

```gdscript
# GOOD
func test_player_cannot_move_while_stunned():
    pass

# AVOID
func test_stun():
    pass
```

### 3. Clean Up Resources

```gdscript
func after_each():
    # Always clean up nodes
    if player:
        player.queue_free()
    
    # Clear any global state
    GameManager.reset()
```

### 4. Test Edge Cases

```gdscript
func test_negative_damage_heals_player():
    player.take_damage(-10)
    assert_eq(player.health, 110)

func test_damage_exceeding_max_health():
    player.take_damage(-200)
    assert_eq(player.health, 100)  # Should cap at max
```

### 5. Use before_each for Setup

```gdscript
func before_each():
    # Create fresh instances for each test
    player = preload("res://scripts/player.gd").new()
    enemy = preload("res://scripts/enemy.gd").new()
    add_child(player)
    add_child(enemy)
```

## Debugging Tests

### Print Debug Info

```gdscript
func test_something():
    gut.p("This is a debug message")
    gut.p("Player health: " + str(player.health))
```

### Pause Before Teardown

```gdscript
func test_something():
    assert_eq(1, 1)
    gut.pause_before_teardown("Pausing to inspect state")
```

### Run Single Test

In the GUT GUI, right-click a test and select "Run" to run just that test.

## Common Issues & Solutions

### Issue: Tests not found

**Solution:** Ensure test files are in directories specified in `gutconfig.json` and file names start with `test_`.

### Issue: Signals not being detected

**Solution:** Call `watch_signals(object)` before emitting the signal.

### Issue: Nodes not being freed

**Solution:** Always call `queue_free()` in `after_each()` or use `add_child()` so GUT can track them.

### Issue: Tests pass individually but fail together

**Solution:** Check for shared state. Use `before_each()` to reset state between tests.

## Resources

- **Official Docs:** https://gut.readthedocs.io
- **GitHub:** https://github.com/bitwes/Gut
- **Examples:** Check `addons/gut/examples/` for sample tests

## Next Steps

1. Create `tests/` folder in your project
2. Write your first test file
3. Run tests via **Tools → GUT → Run Tests**
4. Integrate into your development workflow
5. Add tests to CI/CD pipeline