godot-gdscript-headless-testing

Godot GDScript headless testing (4.x)

Run GDScript tests from the command line, without the editor GUI, and get a real process exit code CI can act on. Targets Godot 4.7 headless CLI.

When to use

• Use when a Godot project has no testing addon installed and needs a fast way to verify GDScript logic (pure functions, resource loading, autoload state) from a terminal or CI pipeline.
• Use when wiring a CI job that must fail the build when a .gd test fails.
• Use when debugging why a godot --headless invocation hangs, opens a window, or exits 0 despite failing assertions.

When not to use: GDScript syntax or language features themselves → godot-gdscript; export/build pipeline and platform templates → godot-export (its own --headless use case, producing a binary, not running tests).

Workflow

1. Confirm the binary resolves headless. Godot 4.x ships --headless built in (no export template needed); run godot --headless --version and confirm it prints a version string, not a GUI window.
2. On a fresh checkout, import before running tests. .godot/ is normally not committed, so a clean checkout has no import cache: class_name types fail to resolve (Identifier "X" not declared in the current scope) and imported assets fail to load (No loader found for resource: res://...). Run godot --headless --path <project_dir> --import once first, in CI and locally.
3. Write the runner as a SceneTree script, not a Node scene. A SceneTree script's _initialize() runs once before any frame — enough for pure-logic tests and no .tscn required to launch.
4. Track pass/fail counts yourself and call quit(<code>) explicitly. Do not use bare assert() to fail a test. Godot does not turn the process exit code non-zero on push_error() by itself — the runner must count failures and call quit(1). Worse, a failed assert() inside _initialize() (official/debug build) prints SCRIPT ERROR: Assertion failed and stops execution before quit() runs, so the process never exits and CI hangs until its own timeout. Use an assert_eq()-style helper that records the failure and keeps going.
5. Invoke with godot --headless --path <project_dir> --script res://<runner>.gd and read the process exit code, not just stdout, from the shell or CI step. --script accepts both a res://-relative path and an absolute filesystem path (e.g. a runner outside the project folder); either works.
6. Redirect stdout and stderr to files when scripting the invocation from a wrapper shell (PowerShell, some CI runners). push_error() output goes to stderr and can be dropped or reordered when only stdout is captured live.
7. Add a step timeout in CI. Even with the assert() pitfall avoided, an await that never resolves (Pattern #2) hangs the runner forever; a timeout-minutes on the CI step is a backstop CI-side, not a substitute for backing every await with a timeout node.