Godot TDD Workflow

Test-driven development for Godot 4.x projects using GdUnit4 testing framework with requirement-first planning and continuous validation.

Workflow Overview

code

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│  Requirements   │ -> │    Planning     │ -> │  TDD Cycle      │
│  Gathering      │    │    & Design     │    │  (Red-Green)    │
└─────────────────┘    └─────────────────┘    └─────────────────┘
     Interview              Plan Mode           LSP + Lint
       Users                                    Validation

Phase 1: Requirements Gathering (需求收集)

BEFORE writing any code, conduct user interview to gather requirements:

Interview Checklist

Ask these questions systematically:

yaml

Core Understanding:
  - What feature/fix is needed? Describe in one sentence.
  - What problem does this solve? Who is affected?
  - What is the expected behavior? Give examples.

User Scenarios:
  - Who are the users? (Players, developers, systems)
  - In what contexts will this be used?
  - What are common edge cases?

Success Criteria:
  - How do we know it's working? (Observable outcomes)
  - What are the performance requirements?
  - Are there constraints (memory, frame rate, file size)?

Integration Points:
  - What existing systems interact? (MessageServer, TileSystem, etc.)
  - What signals need to be emitted/received?
  - What resources (.tres, scenes) are involved?

Testing Strategy:
  - What test cases cover the happy path?
  - What are the critical failure modes?
  - How will we test AutoLoad/singletons?

Example Interview Session

User Request: "Add tile rotation feature"

AI Interview Questions:

•Scope: What does "tile rotation" mean? (Visual only? Data update? Both?)
•Trigger: How does the user initiate rotation? (Click? Keyboard? Drag?)
•Data: Does rotation affect gameplay mechanics? (Connectivity? Combat?)
•UI: What visual feedback shows rotation? (Animation? Instant?)
•Testing: What are the test cases for rotation? (Valid angles? Invalid input?)

Phase 2: Planning Mode (计划模式)

Enter Plan Mode When

•New feature implementation with multiple valid approaches
•Multi-file changes affecting existing systems
•Architectural decisions (pattern selection, data structure)
•Complex requirements requiring exploration

Planning Steps

•

Explore codebase using MCP tools:

code

- Godot MCP: get_project_info, list_projects
- Serena MCP: symbol search, code navigation
- Read: existing implementations, test files

•

Design the approach:

yaml

Architecture:
  - What pattern? (Factory, Observer, State Machine)
  - What classes/files to create/modify?
  - How does it integrate with existing code?

Test Strategy:
  - What test suite? (unit, integration, visual test)
  - How to test dependencies? (mock, stub, fake)
  - What coverage target? (80%+ recommended)

Validation:
  - LSP check: syntax, type safety, symbols
  - Lint check: style, best practices
  - GdUnit4: all tests passing

•

Write implementation plan to Docs/next-steps/plan-{feature}.md:

markdown

# Feature: Tile Rotation

## Requirements Summary
- Rotate tiles 90° increments
- Update connectivity graph
- Emit rotation_complete signal

## Implementation Steps
1. Create `tile_rotator.gd` with rotation logic
2. Add `tile_rotated` signal to Tile class
3. Update connectivity algorithm
4. Create test suite `test_tile_rotator.gd`

## Validation Checklist
- [ ] LSP validation passes
- [ ] Lint check passes
- [ ] All tests passing
- [ ] Coverage >= 80%

•
Present plan to user for approval
•
Only after approval, exit plan mode and implement

Phase 3: TDD Cycle (测试驱动开发)

After plan approval, follow Red-Green-Refactor with continuous validation:

3.1 Red Phase (Write Failing Test)

Generate test stub:

bash

scripts/generate_test_stub.py Scripts/tile/tile_rotator.gd

Write failing test:

gdscript

func test_rotate_clockwise_90_degrees():
    var rotator := TileRotator.new()
    var tile := Tile.new(TileType.FOREST)
    tile.rotation_degrees = 0

    rotator.rotate_clockwise(tile)

    assert_that(tile.rotation_degrees).is_equal(90)
    assert_signal(tile, "tile_rotated").is_emit_count(1)

Validate test code with LSP:

code

- Check syntax
- Verify symbol resolution
- Validate type annotations

3.2 Green Phase (Make Test Pass)

Write minimal implementation:

gdscript

class_name TileRotator
extends Node

signal rotation_completed(tile: Tile)

func rotate_clockwise(tile: Tile) -> void:
    tile.rotation_degrees = (tile.rotation_degrees + 90) % 360
    tile.tile_rotated.emit()
    rotation_completed.emit(tile)

Validate implementation with LSP + Lint:

code

LSP Check:
  - Syntax errors: NONE
  - Type annotations: Valid
  - Symbol resolution: Complete
  - AutoLoad dependencies: Resolved

Lint Check:
  - Naming conventions: snake_case
  - Type hints: Present
  - Docstrings: Added if needed
  - No unused variables

Run test:

bash

scripts/run_quick_test.py test_suites/test_tile_rotator.gd

3.3 Refactor Phase (Improve Code)

Refactor while tests stay green:

gdscript

# Extract common rotation logic
func _rotate_tile(tile: Tile, degrees: int) -> void:
    tile.rotation_degrees = (tile.rotation_degrees + degrees) % 360
    tile.tile_rotated.emit()

Validate refactored code (LSP + Lint + Tests):

bash

# LSP validation
godot-lsp validate Scripts/tile/tile_rotator.gd

# Lint check
scripts/check_lint.py Scripts/tile/tile_rotator.gd

# Run tests
scripts/run_quick_test.py test_suites/test_tile_rotator.gd

Phase 4: Continuous Validation (持续验证)

Validation Pipeline

Every code change must pass:

bash

# 1. LSP Syntax & Type Check
godot-lsp validate <file>

# 2. Lint Style & Best Practices
scripts/check_lint.py <file>

# 3. Run Tests
scripts/run_quick_test.py <test_file>

# 4. Coverage Report
scripts/check_coverage.py --threshold 80

Using Godot MCP for Validation

yaml

Syntax Check:
  tool: godot_lsp_file
  purpose: Syntax validation, type checking, symbol resolution

Code Quality:
  tool: godot_lint_file
  purpose: Style checks, best practices, anti-patterns

Test Execution:
  tool: godot_run_test_file
  purpose: Run specific test suite

Coverage Analysis:
  tool: godot_get_test_coverage
  purpose: Ensure adequate test coverage

Common Scenarios

Scenario 1: New Feature with Dependencies

Flow:

•Interview user about requirements
•Enter plan mode to explore dependencies
•Identify AutoLoad dependencies (MessageServer, etc.)
•Design mock strategy for tests
•Write implementation plan
•Generate test stub for each file
•Write tests with mocks
•Implement feature
•Validate with LSP + Lint + Tests
•Check coverage meets threshold

Scenario 2: Refactoring Existing Code

Flow:

•Interview user about refactoring goals
•Enter plan mode to analyze current code
•Identify test gaps in current coverage
•Write tests for existing behavior (characterization tests)
•Refactor incrementally
•Validate after each change (LSP + Lint + Tests)
•Ensure coverage doesn't decrease

Scenario 3: Bug Fix

Flow:

•Interview user about bug symptoms
•Enter plan mode to locate bug
•Write failing test reproducing bug
•Fix bug with minimal change
•Validate fix (LSP + Lint + Tests pass)
•Add regression tests for similar bugs

Testing Patterns Reference

Testing AutoLoad Singletons

gdscript

func before():
    # Mock MessageServer
    MessageServer = MockMessageServer.new() auto_free.free

func after():
    # Restore real MessageServer
    MessageServer = get_node("/root/MessageServer")

Testing Resources (.tres)

gdscript

func test_load_tile_data():
    var data := load("res://Resources/tile_data.tres") as TileData
    assert_that(data).is_not_null()
    assert_that(data.terrain_types).is_not_empty()

Testing Signals

gdscript

func test_tile_clicked_signal():
    var tile := Tile.new() auto_free.free
    var signal_fired := false

    tile.tile_clicked.connect(func(): signal_fired = true)
    tile.simulate_click()

    assert_that(signal_fired).is_true()

Parameterized Tests

gdscript

func test_rotation_for_all_angles():
    var test_cases := [
        {angle = 0, expected = 90},
        {angle = 90, expected = 180},
        {angle = 270, expected = 0},
    ]

    for case in test_cases:
        var tile := Tile.new()
        tile.rotation_degrees = case.angle
        _rotator.rotate_clockwise(tile)
        assert_that(tile.rotation_degrees).is_equal(case.expected)

Quick Reference

Command Summary

bash

# Requirements & Planning
# (No commands - use interview questions)

# Test Generation
scripts/generate_test_stub.py <path_to_script>

# Testing
scripts/run_quick_test.py <test_file>           # Single file
scripts/run_all_tests.py                        # Full suite

# Validation
godot-lsp validate <file>                       # LSP check
scripts/check_lint.py <file>                    # Lint check
scripts/check_coverage.py --threshold 80        # Coverage

# Godot MCP Tools
godot_run_tests                                 # Full suite
godot_run_test_file <file>                      # Single file
godot_get_test_coverage                         # Coverage report
godot_lint_file <file>                          # Code quality
godot_analyze_dependencies <file>               # Dependencies

MCP Tool Integration

yaml

Planning Phase:
  - godot_get_project_info: Understand project structure
  - godot_list_projects: Find related projects
  - Serena MCP: Symbol search, code navigation

Implementation Phase:
  - godot_lsp_file: Validate syntax & types
  - godot_lint_file: Check code quality
  - godot_run_test_file: Run tests
  - godot_get_test_coverage: Verify coverage

Advanced Guides

See detailed guides:

•patterns.md - AAA, Test Doubles, parameterized tests
•gdunit4_api.md - Complete API reference
•godot_test_guide.md - AutoLoad, scene, signal testing
•examples/ - Working code examples

Best Practices

•Never skip requirements gathering - Always interview user first
•Plan before implementing - Use plan mode for non-trivial tasks
•Validate continuously - LSP → Lint → Tests → Coverage
•Keep tests green - Never commit failing tests
•Maintain coverage - Aim for 80%+ coverage
•Mock dependencies - Use test doubles for AutoLoad, external services
•Test signals - Verify signal emission and handling
•Document edge cases - Add tests for boundary conditions