xpath and windows compatibly (#3)

* feature: allow xpath for test regression against element + Windows support

1) Allow a user to give an optional `xpath` qualifier when calling `screenshot_regression`. The regression will then be tested against this single element instead of the whole page.
2) Make pytest-image-diff with splinter work properly on Windows (see issue #1). Since Windows requires us to close the temp file first, we make the temp file persistent, close it, and then tells splinter to write to it. Afterwards we clean up the temporary file before returning from the function.

* Added windows to CI
* Drop chromedriver-binary from `[splinter]` extra requirement

Co-authored-by: Mats Lindh <[email protected]>

Author: Apkawa

.github/workflows/ci.yml

@@ -9,38 +9,58 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-20.04
-    name: "python ${{ matrix.python-version }} ${{ matrix.toxenv }}"
     strategy:
       fail-fast: false
       matrix:
+        os: [ubuntu-20.04]
         python-version: [ 3.7, 3.8, 3.9, "3.10"]
         toxenv: [""]
         experimental: [ false ]
+        chrome: ["stable"]
         include:
           - toxenv: qa
             python-version: 3.7
             experimental: false
+            os: ubuntu-20.04
           - toxenv: type
             python-version: 3.7
             experimental: false
-          - toxenv: splinter
+            os: ubuntu-20.04
+          - toxenv: splinter-linux
             experimental: false
             python-version: 3.7
+            os: ubuntu-20.04
+
+          - toxenv: splinter-windows
+            # Do not support selenium-windows
+            experimental: true
+            python-version: 3.7
+            os: windows-latest
+            chrome: "959905"
+
+          - experimental: false
+            python-version: "3.9"
+            os: windows-latest
           - experimental: true
             python-version: "3.11.0-alpha - 3.11"
+            os: ubuntu-20.04
           - experimental: true
             python-version: "pypy-3.7"
+            os: ubuntu-20.04
 
+    runs-on: ${{ matrix.os }}
+    name: "${{ matrix.os }} python ${{ matrix.python-version }} ${{ matrix.toxenv }}"
 
     continue-on-error: ${{ matrix.experimental }}
     env:
       TOXENV: ${{ matrix.toxenv }}
     steps:
       # chrome headless
       - uses: browser-actions/setup-chrome@latest
+        with:
+          chrome-version: ${{ matrix.chrome }}
       - uses: actions/checkout@v2
-      - name: Set up python ${{ matrix.python-version}}
+      - name: Set up python ${{ matrix.python-version }}
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}

pytest_image_diff/_types.py

@@ -1,9 +1,10 @@
+from pathlib import Path
 from typing import BinaryIO, Union, Tuple, Optional
 
 from PIL.Image import Image
 from typing_extensions import Literal, Protocol
 
-PathOrFileType = Union[str, bytes, BinaryIO]
+PathOrFileType = Union[str, bytes, Path, BinaryIO]
 ImageFileType = Union[Image, PathOrFileType]
 ImageSize = Tuple[int, int]
 

pytest_image_diff/helpers.py

@@ -1,6 +1,9 @@
 import os
+import pathlib
 import shutil
 import typing
+from contextlib import contextmanager
+from tempfile import NamedTemporaryFile
 
 from PIL.Image import Image
 from _pytest import junitxml
@@ -27,6 +30,19 @@ def build_filename(
     )
 
 
+@contextmanager
+def temp_file(suffix: typing.Optional[str] = None) -> typing.Iterator[pathlib.Path]:
+    with NamedTemporaryFile(suffix=suffix, delete=False) as tf:
+        temp_image_path = pathlib.Path(tf.name)
+    try:
+        yield temp_image_path
+    finally:
+        try:
+            temp_image_path.unlink()
+        except FileNotFoundError:
+            pass
+
+
 class TestInfo:
     test_name: str
     class_name: str
@@ -58,13 +74,13 @@ def get_test_info(
     return TestInfo.get_test_info(request, suffix, prefix)
 
 
-def image_save(image: ImageFileType, path: str) -> None:
+def image_save(image: ImageFileType, path: typing.Union[str, pathlib.Path]) -> None:
     if isinstance(image, Image):
         image.save(path)
     elif isinstance(image, str):
         if not os.path.exists(image):
             raise ValueError("Image maybe path. Path not exists!")
-        shutil.copyfile(image, path)
+        shutil.copyfile(image, str(path))
     elif hasattr(image, "read"):
         with open(path, "wb") as f:
             image = typing.cast(typing.BinaryIO, image)

pytest_image_diff/plugin.py

@@ -1,5 +1,4 @@
 import os
-from tempfile import NamedTemporaryFile
 from typing import Optional, NamedTuple, cast, Callable, Generator
 
 import pytest
@@ -8,7 +7,7 @@
 from _pytest.runner import CallInfo
 
 from ._types import ImageFileType, ImageRegressionCallableType, ImageDiffCallableType
-from .helpers import get_test_info, build_filename, image_save, ensure_dirs
+from .helpers import get_test_info, build_filename, image_save, ensure_dirs, temp_file
 from .image_diff import _diff
 
 try:
@@ -18,7 +17,7 @@
 
 
 @pytest.hookimpl(tryfirst=True, hookwrapper=True)  # type: ignore
-def pytest_runtest_makereport(item: Function, call: CallInfo) -> None:
+def pytest_runtest_makereport(item: Function, call: CallInfo):  # type: ignore
     # execute all other hooks to obtain the report object
     outcome = yield
     rep = outcome.get_result()
@@ -180,8 +179,6 @@ def _factory(
     ) -> bool:
         if threshold is None:
             threshold = image_diff_threshold
-        image_temp_file = NamedTemporaryFile(suffix=".jpg")
-        image_2_temp_file = NamedTemporaryFile(suffix=".jpg")
 
         _info = _image_diff_info(image, suffix)
         diff_path = cast(str, _info.diff_name)
@@ -198,9 +195,12 @@ def _cleanup() -> None:
 
         request.addfinalizer(_cleanup)
 
-        image_save(image, path=image_temp_file.name)
-        image_save(image_2, path=image_2_temp_file.name)
-        diff_ratio = _diff(image_temp_file.name, image_2_temp_file.name, diff_path)
+        with temp_file(suffix=".jpg") as image_temp_file, temp_file(
+            suffix=".jpg"
+        ) as image_2_temp_file:
+            image_save(image, path=image_temp_file)
+            image_save(image_2, path=image_2_temp_file)
+            diff_ratio = _diff(image_temp_file, image_2_temp_file, diff_path)
         assert diff_ratio <= threshold, "Image not equals! See %s" % diff_path  # noqa
         return True
 

pytest_image_diff/splinter.py

@@ -1,8 +1,10 @@
-import pytest
-from tempfile import NamedTemporaryFile
+import os
 from typing import Optional, Generator
+
+import pytest
 from typing_extensions import Protocol
 
+from .helpers import temp_file
 
 try:
     # Check pytest-splinter
@@ -19,6 +21,7 @@ def __call__(
             browser: Optional[Browser] = None,
             threshold: Optional[float] = None,
             suffix: Optional[str] = None,
+            xpath: Optional[str] = "",
         ) -> bool:
             pass
 
@@ -36,22 +39,43 @@ def screenshot_regression(
         :param browser: optional, by default from `browser` fixture
         :param threshold: float, by default from `image_diff_threshold`
         :param suffix: str, need for multiple checks  by one test
+        :param xpath: str, optional xpath expression to select an element to
+                screenshot instead of page
         """
         default_browser = browser
 
         def _factory(
             browser: Optional[Browser] = None,
             threshold: Optional[float] = None,
             suffix: Optional[str] = "",
+            xpath: Optional[str] = "",
         ) -> bool:
             if browser is None:
                 browser = default_browser
 
             if threshold is None:
                 threshold = image_diff_threshold
-            tf = NamedTemporaryFile(suffix=".png")
-            image = tf.name
-            browser.driver.save_screenshot(image)
-            return image_regression(image, threshold, suffix)
+
+            with temp_file(suffix=".png") as temp_image_path:
+                screenshot_path = os.fspath(temp_image_path)
+
+                if xpath:
+                    # `unique_file=False` since we already have a temporary file
+                    #
+                    # Since an xpath screenshot composes its own file name,
+                    # we need to give it the prefix and
+                    # suffix as separate parameters. `:-4` for the path without extension,
+                    # then suffix given manually.
+                    browser.find_by_xpath(xpath).first.screenshot(
+                        screenshot_path[:-4],
+                        suffix=screenshot_path[-4:],
+                        unique_file=False,
+                        full=True,
+                    )
+                else:
+                    browser.driver.save_screenshot(screenshot_path)
+
+                result = image_regression(screenshot_path, threshold, suffix)
+                return result
 
         yield _factory

setup.cfg

@@ -20,7 +20,7 @@ universal = 1
 
 [flake8]
 ignore = D203
-exclude = 
+exclude =
 	.git/,
 	.tox/,
 	docs/,

setup.py

@@ -54,9 +54,7 @@ def read(fname):
     python_requires=">=3.6, <4",
     entry_points={"pytest11": ["image_diff = pytest_image_diff.plugin"]},
     install_requires=["pytest", "typing_extensions", "diffimg", "imgdiff"],
-    extras_require={
-        "splinter": ["pytest-splinter>=2.1.0", "chromedriver-binary==2.40.1"]
-    },
+    extras_require={"splinter": ["pytest-splinter>=2.1.0"]},
     zip_safe=False,
     include_package_data=True,
     keywords=["pytest"],

tests/test_splinter.py

@@ -50,3 +50,14 @@ def test_splinter(browser, screenshot_regression):
     screenshot_regression()
     browser.driver.set_window_size(800, 600)
     screenshot_regression(suffix="small_window")
+
+
+@with_splinter
+def test_splinter_with_xpath(browser, screenshot_regression):
+    tf = tempfile.NamedTemporaryFile(suffix=".html")
+    tf.write(b"<html><body><h1>Example</h1></body></html>")
+    tf.flush()
+
+    browser.driver.set_window_size(1280, 1024)
+    browser.visit("file://" + tf.name)
+    screenshot_regression(xpath="//h1")

tox.ini

@@ -2,13 +2,21 @@
 minversion = 2.3
 skip_missing_interpreters = true
 envlist =
-    py3{6,7,8,9,10,11}
+    py3{6,7,8,9,10,11}-{linux,windows}
 
 [testenv]
+# environment will be skipped if regular expression does not match against the sys.platform string
+platform = linux: linux
+           macos: darwin
+           windows: win32
+
 changedir = {toxinidir}
 deps =
     -r{toxinidir}/requirements-dev.txt
     splinter: -e .[splinter]
+    splinter-linux: chromedriver-binary-auto
+    splinter-windows: chromedriver-binary==95.0.4638.69.0
+
 setenv =
     PYTHONPATH = {toxinidir}
 passenv =