"""Unit tests for visual QA comparison and filmstrip logic.
No Playwright needed — tests only the image comparison engine
and filmstrip generator using synthetic Pillow images.
"""
from __future__ import annotations
from pathlib import Path
import pytest
from PIL import Image
from scripts.visual_qa import compare_screenshots, make_filmstrip
@pytest.fixture
def tmp_img_dir(tmp_path: Path) -> Path:
"""Create a temp directory for test images."""
return tmp_path / "images"
def _make_solid_image(path: Path, color: tuple, size: tuple = (100, 100)) -> Path:
"""Create a solid-color PNG."""
path.parent.mkdir(parents=True, exist_ok=True)
img = Image.new("RGB", size, color)
img.save(str(path))
return path
class TestCompareScreenshots:
"""Tests for compare_screenshots()."""
def test_identical_images_pass(self, tmp_img_dir: Path):
current = _make_solid_image(tmp_img_dir / "current.png", (100, 150, 200))
golden = _make_solid_image(tmp_img_dir / "golden.png", (100, 150, 200))
diff_path = tmp_img_dir / "diff.png"
status, diff_pct, diff_img = compare_screenshots(current, golden, diff_path)
assert status == "pass"
assert diff_pct == 0.0
assert diff_img is None
assert not diff_path.exists()
def test_different_images_fail(self, tmp_img_dir: Path):
current = _make_solid_image(tmp_img_dir / "current.png", (255, 0, 0))
golden = _make_solid_image(tmp_img_dir / "golden.png", (0, 0, 255))
diff_path = tmp_img_dir / "diff.png"
status, diff_pct, diff_img = compare_screenshots(current, golden, diff_path)
assert status == "fail"
assert diff_pct == 100.0
assert diff_img is not None
assert Path(diff_img).exists()
def test_missing_golden_returns_new_baseline(self, tmp_img_dir: Path):
current = _make_solid_image(tmp_img_dir / "current.png", (100, 100, 100))
golden = tmp_img_dir / "nonexistent_golden.png"
diff_path = tmp_img_dir / "diff.png"
status, diff_pct, diff_img = compare_screenshots(current, golden, diff_path)
assert status == "new_baseline"
assert diff_pct == 0.0
assert diff_img is None
def test_size_mismatch_resizes_golden(self, tmp_img_dir: Path):
current = _make_solid_image(
tmp_img_dir / "current.png", (100, 100, 100), size=(200, 200)
)
golden = _make_solid_image(
tmp_img_dir / "golden.png", (100, 100, 100), size=(100, 100)
)
diff_path = tmp_img_dir / "diff.png"
status, diff_pct, diff_img = compare_screenshots(current, golden, diff_path)
assert status == "pass"
assert diff_pct == 0.0
def test_antialiasing_tolerance_passes(self, tmp_img_dir: Path):
"""Small per-pixel differences within tolerance should pass."""
current = _make_solid_image(tmp_img_dir / "current.png", (100, 100, 100))
# Differ by 20 per channel — within default tolerance of 30
golden = _make_solid_image(tmp_img_dir / "golden.png", (120, 120, 120))
diff_path = tmp_img_dir / "diff.png"
status, diff_pct, diff_img = compare_screenshots(
current, golden, diff_path, pixel_tolerance=30
)
assert status == "pass"
assert diff_pct == 0.0
def test_custom_threshold(self, tmp_img_dir: Path):
"""A 50% different image should pass with threshold_pct=60."""
size = (100, 100)
# Create current: top half red, bottom half blue
current_img = Image.new("RGB", size, (255, 0, 0))
for x in range(100):
for y in range(50, 100):
current_img.putpixel((x, y), (0, 0, 255))
current_path = tmp_img_dir / "current.png"
current_path.parent.mkdir(parents=True, exist_ok=True)
current_img.save(str(current_path))
# Golden: all red
golden = _make_solid_image(tmp_img_dir / "golden.png", (255, 0, 0), size)
diff_path = tmp_img_dir / "diff.png"
# With default 1% threshold -> fail
status1, pct1, _ = compare_screenshots(
current_path, golden, diff_path, pixel_tolerance=0
)
assert status1 == "fail"
assert 49.0 < pct1 < 51.0
# With 60% threshold -> pass
status2, pct2, _ = compare_screenshots(
current_path, golden, tmp_img_dir / "diff2.png",
threshold_pct=60.0, pixel_tolerance=0,
)
assert status2 == "pass"
assert 49.0 < pct2 < 51.0
def test_diff_image_shows_differences(self, tmp_img_dir: Path):
"""Diff image should exist and have hot pink pixels where images differ."""
current = _make_solid_image(tmp_img_dir / "current.png", (255, 0, 0))
golden = _make_solid_image(tmp_img_dir / "golden.png", (0, 255, 0))
diff_path = tmp_img_dir / "diff.png"
status, _, diff_img = compare_screenshots(
current, golden, diff_path, pixel_tolerance=0
)
assert status == "fail"
diff = Image.open(diff_img)
# Check a pixel is hot pink (255, 0, 80)
px = diff.getpixel((0, 0))
assert px == (255, 0, 80)
class TestMakeFilmstrip:
"""Tests for make_filmstrip()."""
def test_basic_filmstrip(self, tmp_img_dir: Path):
imgs = []
for i, color in enumerate([(255, 0, 0), (0, 255, 0), (0, 0, 255)]):
p = _make_solid_image(tmp_img_dir / f"img{i}.png", color, size=(100, 200))
imgs.append(p)
output = tmp_img_dir / "strip.png"
result = make_filmstrip(imgs, output, frame_height=100)
assert Path(result).exists()
strip = Image.open(result)
assert strip.height == 100
# 3 frames at 50px each (100 * 100/200) + 2 gaps of 4px
assert strip.width == 50 * 3 + 4 * 2
def test_empty_input_creates_placeholder(self, tmp_img_dir: Path):
output = tmp_img_dir / "empty_strip.png"
result = make_filmstrip([], output)
assert Path(result).exists()
strip = Image.open(result)
assert strip.height == 400
assert strip.width == 200
def test_missing_files_skipped(self, tmp_img_dir: Path):
real = _make_solid_image(tmp_img_dir / "real.png", (100, 100, 100), size=(100, 100))
missing = tmp_img_dir / "ghost.png"
output = tmp_img_dir / "strip.png"
result = make_filmstrip([real, missing], output, frame_height=100)
assert Path(result).exists()
strip = Image.open(result)
# Only one frame: 100px wide scaled to 100px height = 100px
assert strip.width == 100
def test_filmstrip_preserves_aspect_ratio(self, tmp_img_dir: Path):
# Wide image: 400x100
wide = _make_solid_image(tmp_img_dir / "wide.png", (200, 200, 200), size=(400, 100))
output = tmp_img_dir / "strip.png"
make_filmstrip([wide], output, frame_height=200)
strip = Image.open(output)
assert strip.height == 200
# 400x100 scaled to height 200 -> width 800
assert strip.width == 800
