Snapshot testing progress

2025-10-17 02:38:12 +03:00 · 2022-09-16 16:28:48 +01:00
parent e8acba5238
commit d619dae510
10 changed files with 1294 additions and 56 deletions
--- a/docs/examples/guide/layout/grid_layout2.py
+++ b/docs/examples/guide/layout/grid_layout2.py
@@ -4,7 +4,7 @@ from textual.widgets import Static

 class GridLayoutExample(App):
    def compose(self) -> ComposeResult:
-        yield Static("One", classes="box")
+        yield Static("Oneeee", classes="box")
        yield Static("Two", classes="box")
        yield Static("Three", classes="box")
        yield Static("Four", classes="box")
--- a/poetry.lock
+++ b/poetry.lock
@@ -50,14 +50,6 @@ category = "main"
 optional = false
 python-versions = ">=3.5"

-[[package]]
-name = "atomicwrites"
-version = "1.4.1"
-description = "Atomic file writes."
-category = "dev"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-
 [[package]]
 name = "attrs"
 version = "22.1.0"
@@ -67,10 +59,10 @@ optional = false
 python-versions = ">=3.5"

 [package.extras]
-dev = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "mypy (>=0.900,!=0.940)", "pytest-mypy-plugins", "zope.interface", "furo", "sphinx", "sphinx-notfound-page", "pre-commit", "cloudpickle"]
-docs = ["furo", "sphinx", "zope.interface", "sphinx-notfound-page"]
-tests = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "mypy (>=0.900,!=0.940)", "pytest-mypy-plugins", "zope.interface", "cloudpickle"]
-tests_no_zope = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "mypy (>=0.900,!=0.940)", "pytest-mypy-plugins", "cloudpickle"]
+dev = ["cloudpickle", "coverage[toml] (>=5.0.2)", "furo", "hypothesis", "mypy (>=0.900,!=0.940)", "pre-commit", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "sphinx", "sphinx-notfound-page", "zope.interface"]
+docs = ["furo", "sphinx", "sphinx-notfound-page", "zope.interface"]
+tests = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy (>=0.900,!=0.940)", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "zope.interface"]
+tests_no_zope = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy (>=0.900,!=0.940)", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins"]

 [[package]]
 name = "black"
@@ -142,6 +134,14 @@ category = "main"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"

+[[package]]
+name = "colored"
+version = "1.4.3"
+description = "Simple library for color and formatting to terminal"
+category = "dev"
+optional = false
+python-versions = "*"
+
 [[package]]
 name = "commonmark"
 version = "0.9.1"
@@ -204,7 +204,7 @@ python-versions = "*"
 python-dateutil = ">=2.8.1"

 [package.extras]
-dev = ["twine", "markdown", "flake8", "wheel"]
+dev = ["flake8", "markdown", "twine", "wheel"]

 [[package]]
 name = "griffe"
@@ -252,9 +252,9 @@ typing-extensions = {version = ">=3.6.4", markers = "python_version < \"3.8\""}
 zipp = ">=0.5"

 [package.extras]
-docs = ["sphinx", "jaraco.packaging (>=9)", "rst.linker (>=1.9)"]
+docs = ["jaraco.packaging (>=9)", "rst.linker (>=1.9)", "sphinx"]
 perf = ["ipython"]
-testing = ["pytest (>=6)", "pytest-checkdocs (>=2.4)", "pytest-flake8", "pytest-cov", "pytest-enabler (>=1.3)", "packaging", "pyfakefs", "flufl.flake8", "pytest-perf (>=0.9.2)", "pytest-black (>=0.3.7)", "pytest-mypy (>=0.9.1)", "importlib-resources (>=1.3)"]
+testing = ["flufl.flake8", "importlib-resources (>=1.3)", "packaging", "pyfakefs", "pytest (>=6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.3)", "pytest-flake8", "pytest-mypy (>=0.9.1)", "pytest-perf (>=0.9.2)"]

 [[package]]
 name = "iniconfig"
@@ -488,8 +488,8 @@ optional = false
 python-versions = ">=3.7"

 [package.extras]
-docs = ["furo (>=2021.7.5b38)", "proselint (>=0.10.2)", "sphinx-autodoc-typehints (>=1.12)", "sphinx (>=4)"]
-test = ["appdirs (==1.4.4)", "pytest-cov (>=2.7)", "pytest-mock (>=3.6)", "pytest (>=6)"]
+docs = ["furo (>=2021.7.5b38)", "proselint (>=0.10.2)", "sphinx (>=4)", "sphinx-autodoc-typehints (>=1.12)"]
+test = ["appdirs (==1.4.4)", "pytest (>=6)", "pytest-cov (>=2.7)", "pytest-mock (>=3.6)"]

 [[package]]
 name = "pluggy"
@@ -562,18 +562,17 @@ optional = false
 python-versions = ">=3.6.8"

 [package.extras]
-diagrams = ["railroad-diagrams", "jinja2"]
+diagrams = ["jinja2", "railroad-diagrams"]

 [[package]]
 name = "pytest"
-version = "6.2.5"
+version = "7.1.3"
 description = "pytest: simple powerful testing with Python"
 category = "dev"
 optional = false
-python-versions = ">=3.6"
+python-versions = ">=3.7"

 [package.dependencies]
-atomicwrites = {version = ">=1.0", markers = "sys_platform == \"win32\""}
 attrs = ">=19.2.0"
 colorama = {version = "*", markers = "sys_platform == \"win32\""}
 importlib-metadata = {version = ">=0.12", markers = "python_version < \"3.8\""}
@@ -581,10 +580,10 @@ iniconfig = "*"
 packaging = "*"
 pluggy = ">=0.12,<2.0"
 py = ">=1.8.2"
-toml = "*"
+tomli = ">=1.0.0"

 [package.extras]
-testing = ["argcomplete", "hypothesis (>=3.56)", "mock", "nose", "requests", "xmlschema"]
+testing = ["argcomplete", "hypothesis (>=3.56)", "mock", "nose", "pygments (>=2.7.2)", "requests", "xmlschema"]

 [[package]]
 name = "pytest-aiohttp"
@@ -615,7 +614,7 @@ pytest = ">=6.1.0"
 typing-extensions = {version = ">=3.7.2", markers = "python_version < \"3.8\""}

 [package.extras]
-testing = ["coverage (>=6.2)", "hypothesis (>=5.7.1)", "flaky (>=3.5.0)", "mypy (>=0.931)", "pytest-trio (>=0.7.0)"]
+testing = ["coverage (>=6.2)", "flaky (>=3.5.0)", "hypothesis (>=5.7.1)", "mypy (>=0.931)", "pytest-trio (>=0.7.0)"]

 [[package]]
 name = "pytest-cov"
@@ -631,7 +630,7 @@ pytest = ">=4.6"
 toml = "*"

 [package.extras]
-testing = ["fields", "hunter", "process-tests", "six", "pytest-xdist", "virtualenv"]
+testing = ["fields", "hunter", "process-tests", "pytest-xdist", "six", "virtualenv"]

 [[package]]
 name = "python-dateutil"
@@ -687,6 +686,18 @@ category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*"

+[[package]]
+name = "syrupy"
+version = "3.0.0"
+description = "PyTest Snapshot Test Utility"
+category = "dev"
+optional = false
+python-versions = ">=3.7,<4"
+
+[package.dependencies]
+colored = ">=1.3.92,<2.0.0"
+pytest = ">=5.1.0,<8.0.0"
+
 [[package]]
 name = "time-machine"
 version = "2.8.1"
@@ -781,8 +792,8 @@ optional = false
 python-versions = ">=3.7"

 [package.extras]
-docs = ["sphinx", "jaraco.packaging (>=9)", "rst.linker (>=1.9)", "jaraco.tidelift (>=1.4)"]
-testing = ["pytest (>=6)", "pytest-checkdocs (>=2.4)", "pytest-flake8", "pytest-cov", "pytest-enabler (>=1.3)", "jaraco.itertools", "func-timeout", "pytest-black (>=0.3.7)", "pytest-mypy (>=0.9.1)"]
+docs = ["jaraco.packaging (>=9)", "jaraco.tidelift (>=1.4)", "rst.linker (>=1.9)", "sphinx"]
+testing = ["func-timeout", "jaraco.itertools", "pytest (>=6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.3)", "pytest-flake8", "pytest-mypy (>=0.9.1)"]

 [extras]
 dev = ["aiohttp", "click", "msgpack"]
@@ -790,7 +801,7 @@ dev = ["aiohttp", "click", "msgpack"]
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.7"
-content-hash = "61db56567f708cd9ca1c27f0e4a4b4aa3dd808fc8411f80967a90995d7fdd8c8"
+content-hash = "b28791133eec3bbb2debd610593c608c3ec62524be47e803fcbd31e55ddbffee"

 [metadata.files]
 aiohttp = [
@@ -879,7 +890,6 @@ asynctest = [
    {file = "asynctest-0.13.0-py3-none-any.whl", hash = "sha256:5da6118a7e6d6b54d83a8f7197769d046922a44d2a99c21382f0a6e4fadae676"},
    {file = "asynctest-0.13.0.tar.gz", hash = "sha256:c27862842d15d83e6a34eb0b2866c323880eb3a75e4485b079ea11748fd77fac"},
 ]
-atomicwrites = []
 attrs = []
 black = [
    {file = "black-22.6.0-cp310-cp310-macosx_10_9_universal2.whl", hash = "sha256:f586c26118bc6e714ec58c09df0157fe2d9ee195c764f630eb0d8e7ccce72e69"},
@@ -914,7 +924,10 @@ cfgv = [
    {file = "cfgv-3.3.1-py2.py3-none-any.whl", hash = "sha256:c6a0883f3917a037485059700b9e75da2464e6c27051014ad85ba6aaa5884426"},
    {file = "cfgv-3.3.1.tar.gz", hash = "sha256:f5a830efb9ce7a445376bb66ec94c638a9787422f96264c98edc6bdeed8ab736"},
 ]
-charset-normalizer = []
+charset-normalizer = [
+    {file = "charset-normalizer-2.1.1.tar.gz", hash = "sha256:5a3d016c7c547f69d6f81fb0db9449ce888b418b5b9952cc5e6e66843e9dd845"},
+    {file = "charset_normalizer-2.1.1-py3-none-any.whl", hash = "sha256:83e9a75d1911279afd89352c68b45348559d1fc0506b054b346651b5e7fee29f"},
+]
 click = [
    {file = "click-8.1.2-py3-none-any.whl", hash = "sha256:24e1a4a9ec5bf6299411369b208c1df2188d9eb8d916302fe6bf03faed227f1e"},
    {file = "click-8.1.2.tar.gz", hash = "sha256:479707fe14d9ec9a0757618b7a100a0ae4c4e236fac5b7f80ca68028141a1a72"},
@@ -923,19 +936,28 @@ colorama = [
    {file = "colorama-0.4.5-py2.py3-none-any.whl", hash = "sha256:854bf444933e37f5824ae7bfc1e98d5bce2ebe4160d46b5edf346a89358e99da"},
    {file = "colorama-0.4.5.tar.gz", hash = "sha256:e6c6b4334fc50988a639d9b98aa429a0b57da6e17b9a44f0451f930b6967b7a4"},
 ]
+colored = [
+    {file = "colored-1.4.3.tar.gz", hash = "sha256:b7b48b9f40e8a65bbb54813d5d79dd008dc8b8c5638d5bbfd30fc5a82e6def7a"},
+]
 commonmark = [
    {file = "commonmark-0.9.1-py2.py3-none-any.whl", hash = "sha256:da2f38c92590f83de410ba1a3cbceafbc74fee9def35f9251ba9a971d6d66fd9"},
    {file = "commonmark-0.9.1.tar.gz", hash = "sha256:452f9dc859be7f06631ddcb328b6919c67984aca654e5fefb3914d54691aed60"},
 ]
 coverage = []
 distlib = []
-filelock = []
+filelock = [
+    {file = "filelock-3.8.0-py3-none-any.whl", hash = "sha256:617eb4e5eedc82fc5f47b6d61e4d11cb837c56cb4544e39081099fa17ad109d4"},
+    {file = "filelock-3.8.0.tar.gz", hash = "sha256:55447caa666f2198c5b6b13a26d2084d26fa5b115c00d065664b2124680c4edc"},
+]
 frozenlist = []
 ghp-import = [
    {file = "ghp-import-2.1.0.tar.gz", hash = "sha256:9c535c4c61193c2df8871222567d7fd7e5014d835f97dc7b7439069e2413d343"},
    {file = "ghp_import-2.1.0-py3-none-any.whl", hash = "sha256:8337dd7b50877f163d4c0289bc1f1c7f127550241988d568c1db512c4324a619"},
 ]
-griffe = []
+griffe = [
+    {file = "griffe-0.22.0-py3-none-any.whl", hash = "sha256:65c94cba634d6ad397c495b04ed5fd3f06d9b16c4f9f78bd63be9ea34d6b7113"},
+    {file = "griffe-0.22.0.tar.gz", hash = "sha256:a3c25a2b7bf729ecee7cd455b4eff548f01c620b8f58a8097a800caad221f12e"},
+]
 identify = []
 idna = [
    {file = "idna-3.3-py3-none-any.whl", hash = "sha256:84d9dd047ffa80596e0f246e2eab0b391788b0503584e8945f2368256d2735ff"},
@@ -1008,7 +1030,10 @@ mkdocs-autorefs = [
    {file = "mkdocs-autorefs-0.4.1.tar.gz", hash = "sha256:70748a7bd025f9ecd6d6feeba8ba63f8e891a1af55f48e366d6d6e78493aba84"},
    {file = "mkdocs_autorefs-0.4.1-py3-none-any.whl", hash = "sha256:a2248a9501b29dc0cc8ba4c09f4f47ff121945f6ce33d760f145d6f89d313f5b"},
 ]
-mkdocs-material = []
+mkdocs-material = [
+    {file = "mkdocs-material-8.4.2.tar.gz", hash = "sha256:704c64c3fff126a3923c2961d95f26b19be621342a6a4e49ed039f0bb7a5c540"},
+    {file = "mkdocs_material-8.4.2-py2.py3-none-any.whl", hash = "sha256:166287bb0e4197804906bf0389a852d5ced43182c30127ac8b48a4e497ecd7e5"},
+]
 mkdocs-material-extensions = [
    {file = "mkdocs-material-extensions-1.0.3.tar.gz", hash = "sha256:bfd24dfdef7b41c312ede42648f9eb83476ea168ec163b613f9abd12bbfddba2"},
    {file = "mkdocs_material_extensions-1.0.3-py3-none-any.whl", hash = "sha256:a82b70e533ce060b2a5d9eb2bc2e1be201cf61f901f93704b4acf6e3d5983a44"},
@@ -1201,8 +1226,8 @@ pyparsing = [
    {file = "pyparsing-3.0.9.tar.gz", hash = "sha256:2b020ecf7d21b687f219b71ecad3631f644a47f01403fa1d1036b0c6416d70fb"},
 ]
 pytest = [
-    {file = "pytest-6.2.5-py3-none-any.whl", hash = "sha256:7310f8d27bc79ced999e760ca304d69f6ba6c6649c0b60fb0e04a4a77cacc134"},
-    {file = "pytest-6.2.5.tar.gz", hash = "sha256:131b36680866a76e6781d13f101efb86cf674ebb9762eb70d3082b6f29889e89"},
+    {file = "pytest-7.1.3-py3-none-any.whl", hash = "sha256:1377bda3466d70b55e3f5cecfa55bb7cfcf219c7964629b967c37cf0bda818b7"},
+    {file = "pytest-7.1.3.tar.gz", hash = "sha256:4f365fec2dff9c1162f834d9f18af1ba13062db0c708bf7b946f8a5c76180c39"},
 ]
 pytest-aiohttp = [
    {file = "pytest-aiohttp-1.0.4.tar.gz", hash = "sha256:39ff3a0d15484c01d1436cbedad575c6eafbf0f57cdf76fb94994c97b5b8c5a4"},
@@ -1261,6 +1286,10 @@ six = [
    {file = "six-1.16.0-py2.py3-none-any.whl", hash = "sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254"},
    {file = "six-1.16.0.tar.gz", hash = "sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926"},
 ]
+syrupy = [
+    {file = "syrupy-3.0.0-py3-none-any.whl", hash = "sha256:e5e4d376766f46a52a3585365fb90aba0295611043a41a760302d2cd7aa74488"},
+    {file = "syrupy-3.0.0.tar.gz", hash = "sha256:e1e2b6504c85c871fed89b82ce1d02442cf7b622b4b88f95c1332e71e012cd86"},
+]
 time-machine = []
 toml = [
    {file = "toml-0.10.2-py2.py3-none-any.whl", hash = "sha256:806143ae5bfb6a3c6e736a764057db0e6a0e05e338b5630894a5f779cabb4f9b"},
@@ -1296,7 +1325,10 @@ typed-ast = [
    {file = "typed_ast-1.5.4-cp39-cp39-win_amd64.whl", hash = "sha256:0fdbcf2fef0ca421a3f5912555804296f0b0960f0418c440f5d6d3abb549f3e1"},
    {file = "typed_ast-1.5.4.tar.gz", hash = "sha256:39e21ceb7388e4bb37f4c679d72707ed46c2fbf2a5609b8b8ebc4b067d977df2"},
 ]
-typing-extensions = []
+typing-extensions = [
+    {file = "typing_extensions-4.3.0-py3-none-any.whl", hash = "sha256:25642c956049920a5aa49edcdd6ab1e06d7e5d467fc00e0506c44ac86fbfca02"},
+    {file = "typing_extensions-4.3.0.tar.gz", hash = "sha256:e6d2677a32f47fc7eb2795db1dd15c1f34eff616bcaf2cfb5e997f854fa1c4a6"},
+]
 virtualenv = []
 watchdog = [
    {file = "watchdog-2.1.9-cp310-cp310-macosx_10_9_universal2.whl", hash = "sha256:a735a990a1095f75ca4f36ea2ef2752c99e6ee997c46b0de507ba40a09bf7330"},
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,7 +37,7 @@ nanoid = "^2.0.0"
 dev = ["aiohttp", "click", "msgpack"]

 [tool.poetry.dev-dependencies]
-pytest = "^6.2.3"
+pytest = "^7.1.3"
 black = "^22.3.0"
 mypy = "^0.950"
 pytest-cov = "^2.12.1"
@@ -48,6 +48,7 @@ pre-commit = "^2.13.0"
 pytest-aiohttp = "^1.0.4"
 time-machine = "^2.6.0"
 Jinja2 = "<3.1.0"
+syrupy = "^3.0.0"

 [tool.black]
 includes = "src"
@@ -55,8 +56,10 @@ includes = "src"
 [tool.pytest.ini_options]
 asyncio_mode = "auto"
 testpaths = ["tests"]
+addopts = "--strict-markers"
 markers = [
    "integration_test: marks tests as slow integration tests (deselect with '-m \"not integration_test\"')",
+    "snapshot: marks test as a snapshot test",
 ]

 [build-system]
--- a/src/textual/_doc.py
+++ b/src/textual/_doc.py
@@ -3,15 +3,16 @@ from __future__ import annotations
 import runpy
 import os
 import shlex
-from typing import cast, TYPE_CHECKING
+from typing import cast, TYPE_CHECKING, Iterable

 if TYPE_CHECKING:
    from textual.app import App

+
 # This module defines our "Custom Fences", powered by SuperFences
 # @link https://facelessuser.github.io/pymdown-extensions/extensions/superfences/#custom-fences
 def format_svg(source, language, css_class, options, md, attrs, **kwargs) -> str:
-    """A superfences formatter to insert a SVG screenshot."""
+    """A superfences formatter to insert an SVG screenshot."""

    try:
        cmd: list[str] = shlex.split(attrs["path"])
@@ -21,25 +22,13 @@ def format_svg(source, language, css_class, options, md, attrs, **kwargs) -> str
        press = [*_press.split(",")] if _press else ["_"]
        title = attrs.get("title")

-        os.environ["COLUMNS"] = attrs.get("columns", "80")
-        os.environ["LINES"] = attrs.get("lines", "24")
-
        print(f"screenshotting {path!r}")

        cwd = os.getcwd()
        try:
-            app_vars = runpy.run_path(path)
-            if "sys" in app_vars:
-                app_vars["sys"].argv = cmd
-            app: App = cast("App", app_vars["app"])
-            app.run(
-                quit_after=5,
-                press=press or ["ctrl+c"],
-                headless=True,
-                screenshot=True,
-                screenshot_title=title,
-            )
-            svg = app._screenshot
+            rows = int(attrs.get("lines", 24))
+            columns = int(attrs.get("columns", 80))
+            svg = take_svg_screenshot(path, press, title, terminal_size=(rows, columns))
        finally:
            os.chdir(cwd)

@@ -52,8 +41,40 @@ def format_svg(source, language, css_class, options, md, attrs, **kwargs) -> str
        traceback.print_exception(error)


+def take_svg_screenshot(
+    app_path: str,
+    press: Iterable[str] = ("_",),
+    title: str | None = None,
+    terminal_size: tuple[int, int] = (24, 80),
+) -> str:
+    rows, columns = terminal_size
+
+    os.environ["COLUMNS"] = str(columns)
+    os.environ["LINES"] = str(rows)
+
+    app_vars = runpy.run_path(app_path)
+    if "sys" in app_vars:
+        cmd: list[str] = shlex.split(app_path)
+        app_vars["sys"].argv = cmd
+
+    app: App = cast("App", app_vars["app"])
+
+    if title is None:
+        title = app.title
+
+    app.run(
+        quit_after=5,
+        press=press or ["ctrl+c"],
+        headless=True,
+        screenshot=True,
+        screenshot_title=title,
+    )
+    svg = app._screenshot
+    return svg
+
+
 def rich(source, language, css_class, options, md, attrs, **kwargs) -> str:
-    """A superfences formatter to insert a SVG screenshot."""
+    """A superfences formatter to insert an SVG screenshot."""

    from rich.console import Console
    import io
--- a/tests/snapshot_tests/init.py
+++ b/tests/snapshot_tests/init.py
--- a/tests/snapshot_tests/snapshots/test_snapshots.ambr
+++ b/tests/snapshot_tests/snapshots/test_snapshots.ambr
--- a/tests/snapshot_tests/conftest.py
+++ b/tests/snapshot_tests/conftest.py
@@ -0,0 +1,178 @@
+import difflib
+from dataclasses import dataclass
+from datetime import datetime
+from functools import partial
+from operator import attrgetter
+from os import PathLike
+from pathlib import Path
+from typing import Union, List, Optional, Any, Callable
+
+import pytest
+from _pytest.fixtures import FixtureDef, SubRequest, FixtureRequest
+from jinja2 import Template
+from rich.console import Console
+from rich.panel import Panel
+
+from textual._doc import take_svg_screenshot
+
+snapshot_svg_key = pytest.StashKey[str]()
+actual_svg_key = pytest.StashKey[str]()
+snapshot_pass = pytest.StashKey[bool]()
+
+
+@pytest.fixture
+def snap_compare(snapshot, request: FixtureRequest) -> Callable[[str], bool]:
+    def compare(app_path: str, snapshot) -> bool:
+        node = request.node
+        actual_screenshot = take_svg_screenshot(app_path)
+        result = snapshot == actual_screenshot
+
+        if result is False:
+            # The split and join below is a mad hack, sorry...
+            node.stash[snapshot_svg_key] = "\n".join(str(snapshot).splitlines()[1:-1])
+            node.stash[actual_svg_key] = actual_screenshot
+        else:
+            node.stash[snapshot_pass] = True
+
+        return result
+
+    return partial(compare, snapshot=snapshot)
+
+
+@dataclass
+class SvgSnapshotDiff:
+    snapshot: Optional[str]
+    actual: Optional[str]
+    test_name: str
+    file_similarity: float
+    path: PathLike
+    line_number: int
+
+
+#
+# def pytest_runtestloop(session: "Session") -> Optional[object]:
+
+@pytest.hookimpl(hookwrapper=True)
+def pytest_pyfunc_call(pyfuncitem: "pytest.Function") -> Optional[object]:
+    """Call underlying test function.
+
+    Stops at first non-None result, see :ref:`firstresult`.
+    """
+    # Before
+    yield
+    # After
+
+
+def pytest_runtest_teardown(item: pytest.Item, nextitem: Optional[pytest.Item]) -> None:
+    """Called to perform the teardown phase for a test item.
+
+    The default implementation runs the finalizers and calls ``teardown()``
+    on ``item`` and all of its parents (which need to be torn down). This
+    includes running the teardown phase of fixtures required by the item (if
+    they go out of scope).
+
+    :param nextitem:
+        The scheduled-to-be-next test item (None if no further test item is
+        scheduled). This argument is used to perform exact teardowns, i.e.
+        calling just enough finalizers so that nextitem only needs to call
+        setup functions.
+    """
+
+
+@pytest.hookimpl(hookwrapper=True)
+def pytest_fixture_setup(
+    fixturedef: FixtureDef[Any], request: SubRequest
+) -> Optional[object]:
+    """Perform fixture setup execution.
+
+    :returns: The return value of the call to the fixture function.
+
+    Stops at first non-None result, see :ref:`firstresult`.
+
+    .. note::
+        If the fixture function returns None, other implementations of
+        this hook function will continue to be called, according to the
+        behavior of the :ref:`firstresult` option.
+    """
+    value = yield
+    value = value.get_result()
+    value = repr(value)
+
+
+def pytest_sessionfinish(
+    session: "pytest.Session",
+    exitstatus: Union[int, "pytest.ExitCode"],
+) -> None:
+    """Called after whole test run finished, right before returning the exit status to the system.
+
+    :param pytest.Session session: The pytest session object.
+    :param int exitstatus: The status which pytest will return to the system.
+    """
+    diffs: List[SvgSnapshotDiff] = []
+    num_snapshots_passing = 0
+    for item in session.items:
+        num_snapshots_passing += int(item.stash.get(snapshot_pass, False))
+        snapshot_svg = item.stash.get(snapshot_svg_key, None)
+        actual_svg = item.stash.get(actual_svg_key, None)
+        if snapshot_svg and actual_svg:
+            path, line_index, name = item.reportinfo()
+            diffs.append(
+                SvgSnapshotDiff(
+                    snapshot=str(snapshot_svg),
+                    actual=str(actual_svg),
+                    file_similarity=100 * difflib.SequenceMatcher(a=str(snapshot_svg), b=str(actual_svg)).ratio(),
+                    test_name=name,
+                    path=path,
+                    line_number=line_index + 1,
+                )
+            )
+
+    diff_sort_key = attrgetter("file_similarity")
+    diffs = sorted(diffs, key=diff_sort_key)
+
+    conftest_path = Path(__file__)
+    snapshot_template_path = conftest_path.parent / "snapshot_report_template.jinja2"
+    snapshot_report_path = conftest_path.parent / "snapshot_report.html"
+
+    template = Template(snapshot_template_path.read_text())
+
+    num_fails = len(diffs)
+    num_snapshot_tests = len(diffs) + num_snapshots_passing
+
+    rendered_report = template.render(
+        diffs=diffs,
+        passes=num_snapshots_passing,
+        fails=num_fails,
+        pass_percentage=100*(num_snapshots_passing/num_snapshot_tests),
+        fail_percentage=100*(num_fails/num_snapshot_tests),
+        num_snapshot_tests=num_snapshot_tests,
+        now=datetime.utcnow()
+    )
+    with open(snapshot_report_path, "wt") as snapshot_file:
+        snapshot_file.write(rendered_report)
+
+    session.config._textual_snapshots = diffs
+    session.config._textual_snapshot_html_report = snapshot_report_path
+
+
+def pytest_terminal_summary(
+    terminalreporter: "pytest.TerminalReporter",
+    exitstatus: pytest.ExitCode,
+    config: pytest.Config,
+) -> None:
+    """Add a section to terminal summary reporting.
+
+    :param _pytest.terminal.TerminalReporter terminalreporter: The internal terminal reporter object.
+    :param int exitstatus: The exit status that will be reported back to the OS.
+    :param pytest.Config config: The pytest config object.
+
+    .. versionadded:: 4.2
+        The ``config`` parameter.
+    """
+    diffs = config._textual_snapshots
+    snapshot_report_location = config._textual_snapshot_html_report
+    console = Console()
+    summary_panel = Panel(
+        f"[b]Report available for {len(diffs)} snapshot test failures.[/]\n\nView the report at:\n\n[blue]{snapshot_report_location}[/]",
+        title="[b red]Textual Snapshot Test Summary", padding=1)
+    console.print(summary_panel)
--- a/tests/snapshot_tests/snapshot_report.html
+++ b/tests/snapshot_tests/snapshot_report.html
--- a/tests/snapshot_tests/snapshot_report_template.jinja2
+++ b/tests/snapshot_tests/snapshot_report_template.jinja2
@@ -0,0 +1,98 @@
+<!doctype html>
+<html lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>Textual Snapshot Test Report</title>
+    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.1/dist/css/bootstrap.min.css" rel="stylesheet"
+          integrity="sha384-iYQeCzEYFbKjA/T2uDLTpkwGzCiq6soy8tYaI1GyVh/UjpbCx/TYkiZhlZB6+fzT" crossorigin="anonymous">
+</head>
+<body>
+<div class="container-fluid">
+    <div class="row mb-4" style="background-color:#F4F8F7;">
+        <div class="col-8 p-4">
+            <h4>
+                <strong>Textual</strong> Snapshot Tests
+            </h4>
+            <span class="text-muted">Showing diffs for {{ fails }} mismatched snapshot(s)</span>
+        </div>
+        <div class="col p-4">
+            <div class="w-100 d-flex justify-content-end mb-1 mt-2">
+                <span class="text-danger">
+                    <strong>{{ diffs | length }}</strong> snapshots changed
+                </span>
+                <span class="text-muted mx-2">
+                    ·
+                </span>
+                <span class="text-success">
+                    <strong>{{ passes }}</strong> snapshots matched
+                </span>
+            </div>
+            <div class="progress">
+                <div class="progress-bar bg-danger" role="progressbar" aria-label="Segment one"
+                     style="width: {{ fail_percentage }}%"
+                     aria-valuenow="{{ fails }}" aria-valuemin="0" aria-valuemax="{{ num_snapshot_tests }}"></div>
+                <div class="progress-bar bg-success" role="progressbar" aria-label="Segment two"
+                     style="width: {{ pass_percentage }}%"
+                     aria-valuenow="{{ num_snapshot_tests }}" aria-valuemin="0"
+                     aria-valuemax="{{ num_snapshot_tests }}"></div>
+            </div>
+        </div>
+    </div>
+
+    {% for diff in diffs %}
+        <div class="row mb-4">
+            <div class="col">
+                <div class="card">
+                    <div class="card-header d-flex justify-content-between">
+                        <div>
+                            <strong class="font-monospace">
+                                {{ diff.test_name }}
+                            </strong>
+                            <span class="text-muted">({{ "%.2f"|format(diff.file_similarity) }}% similar)</span>
+                        </div>
+                        <span class="text-muted">{{ diff.path }}:{{ diff.line_number }}</span>
+                    </div>
+                    <div class="card-body">
+                        <div class="row">
+                            <div class="col">
+                                {{ diff.actual }}
+                                <div class="w-100 d-flex justify-content-center mt-1">
+                                    <span class="small">Output from test</span>
+                                </div>
+                            </div>
+                            <div class="col">
+                                {{ diff.snapshot }}
+                                <div class="w-100 d-flex justify-content-center mt-1">
+                                    <span class="small">Historical snapshot</span>
+                                </div>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+            </div>
+        </div>
+    {% endfor %}
+
+    <div class="row" style="background-color:#F4F8F7;">
+        <div class="col">
+            <div class="card bg-light">
+                <div class="card-body">
+                    <p class="card-text">If you're happy with the change, run pytest with the <span class="font-monospace text-primary">--snapshot-update</span> flag to update the snapshot.</p>
+                </div>
+            </div>
+        </div>
+    </div>
+
+<div class="row">
+    <div class="col">
+        <div class="w-100 d-flex p-4 justify-content-center">
+            <p class="text-muted">Report generated at UTC {{ now }}.</p>
+        </div>
+    </div>
+</div>
+
+</div>
+
+</body>
+</html>
--- a/tests/snapshot_tests/test_snapshots.py
+++ b/tests/snapshot_tests/test_snapshots.py
@@ -0,0 +1,14 @@
+def test_grid_layout_basic(snap_compare):
+    assert snap_compare("docs/examples/guide/layout/grid_layout1.py")
+
+
+def test_grid_layout_basic_overflow(snap_compare):
+    assert snap_compare("docs/examples/guide/layout/grid_layout2.py")
+
+
+def test_combining_layouts(snap_compare):
+    assert snap_compare("docs/examples/guide/layout/combining_layouts.py")
+
+
+def test_layers(snap_compare):
+    assert snap_compare("docs/examples/guide/layout/layers.py")