fix(tests): decoding PNG files to fix Linux/Mac differences in encoding

ci/prepare_ui_artifacts.py

@@ -1,27 +1,19 @@
-import hashlib
-import json
 import shutil
+import sys
 from pathlib import Path
 
+ROOT = Path(__file__).parent / ".."
+sys.path.insert(0, str(ROOT))
+# Needed for setup purposes, filling the FILE_HASHES dict
+from tests.ui_tests import read_fixtures  # isort:skip
 
-def _hash_files(path):
-    files = path.iterdir()
-    hasher = hashlib.sha256()
-    for file in sorted(files):
-        hasher.update(file.read_bytes())
+read_fixtures()
+from tests.ui_tests import _hash_files, FILE_HASHES, SCREENS_DIR  # isort:skip
 
-    return hasher.digest().hex()
 
-
-root = Path(__file__).parent / ".."
-screens = root / "tests/ui_tests/screens"
-fixtures = root / "tests/ui_tests/fixtures.json"
-
-hashes = json.loads(fixtures.read_text())
-
-for test_case in hashes.keys():
-    recorded_dir = screens / test_case / "recorded"
-    expected_hash = hashes[test_case]
+for test_case in FILE_HASHES.keys():
+    recorded_dir = SCREENS_DIR / test_case / "recorded"
+    expected_hash = FILE_HASHES[test_case]
     actual_hash = _hash_files(recorded_dir)
     assert expected_hash == actual_hash
-    shutil.make_archive(root / "ci/ui_test_records" / actual_hash, "zip", recorded_dir)
+    shutil.make_archive(ROOT / "ci/ui_test_records" / actual_hash, "zip", recorded_dir)

tests/ui_tests/__init__.py

@@ -7,10 +7,12 @@ from pathlib import Path
 
 import pytest
 from _pytest.outcomes import Failed
+from PIL import Image
 
 from .reporting import testreport
 
 UI_TESTS_DIR = Path(__file__).parent.resolve()
+SCREENS_DIR = UI_TESTS_DIR / "screens"
 HASH_FILE = UI_TESTS_DIR / "fixtures.json"
 SUGGESTION_FILE = UI_TESTS_DIR / "fixtures.suggestion.json"
 FILE_HASHES = {}
@@ -45,15 +47,24 @@ def _rename_records(screen_path):
         record.replace(screen_path / f"{index:08}.png")
 
 
-def _hash_files(path):
+def _hash_files(path: Path) -> str:
     files = path.iterdir()
     hasher = hashlib.sha256()
     for file in sorted(files):
-        hasher.update(file.read_bytes())
+        hasher.update(_get_bytes_from_png(str(file)))
 
     return hasher.digest().hex()
 
 
+def _get_bytes_from_png(png_file: str) -> bytes:
+    """Decode a PNG file into bytes representing all the pixels.
+
+    Is necessary because Linux and Mac are using different PNG encoding libraries,
+    and we need the file hashes to be the same on both platforms.
+    """
+    return Image.open(png_file).tobytes()
+
+
 def _process_tested(fixture_test_path, test_name):
     PROCESSED.add(test_name)
 
@@ -85,7 +96,7 @@ def _process_tested(fixture_test_path, test_name):
 def screen_recording(client, request):
     test_ui = request.config.getoption("ui")
     test_name = get_test_name(request.node.nodeid)
-    screens_test_path = UI_TESTS_DIR / "screens" / test_name
+    screens_test_path = SCREENS_DIR / test_name
 
     if test_ui == "record":
         screen_path = screens_test_path / "recorded"
@@ -144,7 +155,7 @@ def _get_fixtures_content(fixtures: dict, remove_missing: bool):
 
 def main():
     read_fixtures()
-    for record in (UI_TESTS_DIR / "screens").iterdir():
+    for record in SCREENS_DIR.iterdir():
         if not (record / "actual").exists():
             continue