feat(test): add visual regression testing

Will upload screenshots on failure.

.github/workflows/main.yml

@@ -305,6 +305,12 @@ jobs:
           if grep -q 'SCRIPT_ERROR:' output.log || grep -q 'Tests             none' output.log; then
             exit 1
           fi
+      - name: Upload screenshots
+        uses: actions/upload-artifact@v4
+        if: failure()
+        with:
+          name: failed-screenshots
+          path: test/visual_regression/screenshots
 
   merge-artifacts:
     name: Merge Artifacts

.gitignore

@@ -30,6 +30,7 @@ mono_crash.*
 .gutconfig.json
 test/results.xml
 test/test_metadata.json
+test/visual_regression/screenshots/
 
 # GodotXterm-specific ignores
 .gdxterm

Justfile

@@ -22,7 +22,7 @@ test:
     {{godot}} --headless -s addons/gut/gut_cmdln.gd -gtest={{test_files}} -gexit
 
 test-all:
-    {{godot}} --windowed --resolution 400x200 --position 0,0 -s addons/gut/gut_cmdln.gd -gdir=res://test -gopacity=0 -gexit
+    {{godot}} --windowed --resolution 400x200 --position 0,0 -s addons/gut/gut_cmdln.gd -gdir=res://test -ginclude_subdirs=true -gopacity=0 -gexit
 
 test-rendering:
     {{godot}} --windowed --resolution 400x200 --position 0,0 -s addons/gut/gut_cmdln.gd -gtest=res://test/test_rendering.gd -gopacity=0 -gexit

plug.gd

@@ -5,3 +5,4 @@ extends "res://addons/gd-plug/plug.gd"
 
 func _plugging():
 	plug("bitwes/Gut", {tag = "v9.2.0"})
+	plug("lihop/godot-pixelmatch", {tag = "v2.0.0", include = ["addons/pixelmatch"]})

test/visual_regression/test_visual_regression.gd

@@ -0,0 +1,96 @@
+# SPDX-FileCopyrightText: 2024 Leroy Hopson <godot-xterm@leroy.nix.nz>
+# SPDX-License-Identifier: MIT
+
+class_name VisualRegressionTest extends RenderingTest
+
+const Pixelmatch = preload("res://addons/pixelmatch/pixelmatch.gd")
+const MenuScene = preload("res://examples/menu/menu.tscn")
+
+const TERMINAL_SIZE = Vector2i(200, 100)
+const UPDATE = false  # Set to true when you want to update baseline images.
+
+var matcher = Pixelmatch.new()
+
+
+func get_described_class():
+	return Terminal
+
+
+func before_each():
+	await super.before_each()
+	subject.set_anchors_and_offsets_preset(Control.PRESET_TOP_LEFT)
+	subject.call_deferred("set_size", TERMINAL_SIZE)
+	await wait_for_signal(subject.size_changed, 5)
+
+
+func assert_match(reference: String):
+	var image = get_viewport().get_texture().get_image()
+	image.crop(TERMINAL_SIZE.x, TERMINAL_SIZE.y)
+	var reference_path = "res://test/visual_regression/baseline/%s.png" % reference
+
+	if UPDATE or not FileAccess.file_exists(reference_path):
+		image.save_png(reference_path)
+
+	var reference_image = Image.new()
+	reference_image.load(reference_path)
+	assert(reference_image, "Could not load reference image: " + reference)
+	var diff_image = Image.create(TERMINAL_SIZE.x, TERMINAL_SIZE.y, false, Image.FORMAT_RGBA8)
+	var diff = matcher.diff(image, reference_image, diff_image, TERMINAL_SIZE.x, TERMINAL_SIZE.y)
+
+	if diff != 0:
+		diff_image.save_png("res://test/visual_regression/screenshots/%s.diff.png" % reference)
+		image.save_png("res://test/visual_regression/screenshots/%s.png" % reference)
+
+	assert_eq(diff, 0, "Screenshot matches baseline image")
+
+
+class TestVisualRegression:
+	extends VisualRegressionTest
+
+	func test_empty():
+		await wait_frames(30)
+		assert_match("empty")
+
+	func test_default_theme():
+		# Print every background color.
+		for i in range(8):
+			subject.write("\u001b[4%dm " % i)  # Regular.
+
+			# Print every foreground color.
+
+			# Print every font.
+		for i in range(8):
+			subject.write("\u001b[10%dm " % i)  # Bright.
+
+			# Print every foreground color.
+
+			# Print every font.
+		subject.write("\u001b[0m")  # Reset.
+
+		# Print every foreground color.
+		for i in range(8):
+			subject.write("\u001b[3%dm█" % i)  # Regular.
+
+			# Print every font.
+		for i in range(8):
+			subject.write("\u001b[9%dm█" % i)  # Bright.
+
+			# Print every font.
+		subject.write("\u001b[0m")  # Reset.
+
+		# Print every font.
+		subject.write("L\u001b[0m")  # Regular.
+		subject.write("\u001b[1mL\u001b[0m")  # Bold.
+		subject.write("\u001b[3mL\u001b[0m")  # Italic.
+		subject.write("\u001b[1m\u001b[3mL\u001b[0m")  # Bold Italic.
+
+		await wait_frames(30)
+		assert_match("default_theme")
+
+	func test_transparency():
+		subject.add_theme_color_override("foreground_color", Color(0, 1, 0, 0.5))
+		subject.add_theme_color_override("background_color", Color(1, 0, 0, 0.5))
+		subject.write("bg red, 50% transparency\r\n")
+		subject.write("fg green, 50% transparency")
+		await wait_frames(30)
+		assert_match("transparency")