New snapshot code

Author: hansthen

.pre-commit-config.yaml

@@ -11,6 +11,7 @@ repos:
     - id: check-docstring-first
       exclude: ^examples/streamlit
     - id: check-added-large-files
+      args: ['--maxkb=1024']
     - id: requirements-txt-fixer
     - id: file-contents-sorter
       files: requirements-dev.txt

tests/screenshots/screenshot_issue_1877.png

@@ -0,0 +1,42 @@
+import importlib
+import io
+import os
+import shutil
+
+import pytest
+from PIL import Image
+from pixelmatch.contrib.PIL import pixelmatch
+from selenium import webdriver
+
+options = webdriver.chrome.options.Options()
+options.add_argument("--headless")
+
+
+paths = os.listdir("tests/regressions/")
+paths = [p.replace(".py", "") for p in paths if p.endswith(".py")]
+
+
+@pytest.mark.parametrize("path", paths)
+def test_screenshot(path: str):
+    driver = webdriver.Chrome(options=options)
+    m = importlib.import_module(f"tests.regressions.{path}").m
+    img_data = m._to_png(3, driver=driver, size=(800, 800))
+    img_a = Image.open(io.BytesIO(img_data))
+    img_a.save(f"/tmp/screenshot_new_{path}.png")
+
+    if os.path.exists(f"tests/screenshots/screenshot_{path}.png"):
+        img_b = Image.open(f"tests/screenshots/screenshot_{path}.png")
+
+        img_diff = Image.new("RGBA", img_a.size)
+        # note how there is no need to specify dimensions
+        mismatch = pixelmatch(img_a, img_b, img_diff, threshold=0.2, includeAA=False)
+
+        img_diff.save(f"/tmp/screenshot_diff_{path}.png")
+        assert mismatch < 1500
+
+    else:
+        shutil.copy(
+            f"/tmp/screenshot_new_{path}.png",
+            f"tests/screenshots/screenshot_{path}.png",
+        )
+        raise Exception("no screenshot available, generating new")