fix(assertions): accept pseudo in not_to_have_css (#3261)

Author: pavelfeldman

.claude/skills/playwright-release/SKILL.md

@@ -106,7 +106,7 @@ Open a PR from the branch with the roll commit:
   release version, even when `DRIVER_VERSION` is a beta build.
 - Description: the release notes from step 2, in GitHub markdown (see below).
   The user copies this description into the GitHub release, so for this PR it
-  replaces the "keep PR descriptions short" rule in `CLAUDE.md`.
+  replaces the "keep PR descriptions short" rule in `AGENTS.md`.
 
 Convert the notes to GitHub markdown yourself:
 

.claude/skills/playwright-roll/SKILL.md

@@ -281,9 +281,11 @@ After the script settles, run `pre-commit run --all-files` once more to confirm
 
 ### 6. Add tests
 
-For each PORT, add one async test and a matching sync test. Conventions:
+For each PORT, port the upstream test that covers it, as an async test and a matching sync test. Conventions:
 
-- Tests go in the existing topic file (`test_page_network_request.py`, `test_browsercontext.py`, `test_dialog.py`, …) — don't create new files unless there's no obvious home.
+- The upstream file decides the Python file: `tests/page/expect-misc.spec.ts` becomes `tests/async/test_expect_misc.py` and `tests/sync/test_expect_misc.py`. Create the file if it does not exist.
+- The upstream title decides the test name: the `describe` title and the test title, in snake_case. `test('should support pseudo element')` in `test.describe('toHaveCSS')` becomes `test_to_have_css_should_support_pseudo_element`.
+- When no upstream test covers the change, extend an existing test before you add a new one.
 - Use `from playwright.async_api import …`, **not** `from playwright._impl._page import Page` (the impl class doesn't have the public wrappers like `expect_console_message`).
 - For event-info objects, `await message_info.value` (it's an `async` property).
 - Don't write tests that hang the page (e.g. `page.evaluate(... fetch slow ...)` followed by `page.close()` from a fixture) — the request task gets a `TargetClosedError`. Use `page.on("event", handler)` to capture state at event time instead.

CLAUDE.md AGENTS.mdCLAUDE.md renamed to AGENTS.md

@@ -1,6 +1,6 @@
-# CLAUDE.md
+# AGENTS.md
 
-Guidance for Claude when working in this repository.
+Guidance for coding agents working in this repository.
 
 ## What this is
 
@@ -14,7 +14,7 @@ Python bindings for [Playwright](https://playwright.dev). The Python client talk
 - `scripts/codegen/python_rules.js` — the Python facts that the docs do not contain (positional options, struct `total=`, hidden members and options). Policy: the shipped Python API wins; each entry is a candidate for an upstream docs fix, and the generator fails on entries that no longer match anything. Every entry needs a one-line rationale comment above it.
 - `playwright/_impl/_protocol.py` — **auto-generated** by `scripts/codegen/generate_protocol.py` (run by `./scripts/update_api.sh`) from the upstream protocol spec: the parameters of every command. With `PW_CHECK_PROTOCOL=1`, `playwright/_impl/_protocol_check.py` checks each message that the client sends against it. The test suite sets this, and fails a test that sends an unknown command, an unknown or missing parameter, or a value of the wrong type.
 - `scripts/codegen/compare_api.py` — compares two generated files (signatures, annotations, call bodies, docstrings) and lists every difference. Use it to check that a generator change does not change the API.
-- `tests/async/`, `tests/sync/` — pytest suites. Most new tests are added to the async file with a sync mirror.
+- `tests/async/`, `tests/sync/` — pytest suites, ported from the upstream tests. Most new tests are added to the async file with a sync mirror. See [Tests](#tests).
 - `DRIVER_VERSION` — the single source of truth for which Playwright release the driver is assembled from (one line, the `playwright-core` npm version, e.g. `1.61.0`, no `v` prefix). Read by `setup.py`, `scripts/build_driver.py`, and CI. The wheel build downloads `playwright-core` at this version from npm plus the matching Node.js binary and assembles the per-platform bundles — no source build. The version is baked into the staged bundle filenames (`driver/playwright-<version>-<suffix>.zip`), so it doubles as the build cache key.
 - `NODE_VERSION` — the Node.js version bundled with the driver (one line, e.g. `24.16.0`). Maintained at roll time by `scripts/update_node_version.py` (latest LTS, mirroring upstream's `utils/build/update-playwright-node.mjs`).
 - `scripts/build_driver.py` — assembles the per-platform driver bundles into `driver/` by downloading the `playwright-core` npm package (`DRIVER_VERSION`) and the official Node.js binaries (`NODE_VERSION`). Fetches `playwright-core` with `npm pack` (needs Node.js/npm on PATH; honours a root `.npmrc`) and the Node.js binaries over plain HTTP; invoked from `setup.py`'s `bdist_wheel` with the target platform's suffix (no arg builds all six).
@@ -45,6 +45,23 @@ If the system lacks `python3-venv`, `uv venv env` is an acceptable substitute (t
 
 The public API comes from the upstream docs. After `./scripts/update_api.sh`, run `mypy playwright`: the generated classes type their `_impl_obj`, so every new member or option that `_impl/` does not implement yet is a mypy error in `_generated.py`. Fix it in `_impl/`, or record a justified difference in `scripts/codegen/python_rules.js` — not by hand-editing `_generated.py`.
 
+## Tests
+
+The tests are a port of the upstream tests in `microsoft/playwright` (`tests/page/`, `tests/library/`). Keep them close to upstream, so that each upstream test has one place in this repo.
+
+**First rule: follow the upstream names and files.**
+
+- When a change needs a test, find the upstream test for the same behavior and port it. Do not write a new test when an upstream test exists.
+- Put the test in the Python file that matches the upstream file: `tests/page/expect-misc.spec.ts` becomes `tests/async/test_expect_misc.py`. If that file does not exist, create it.
+- Name the test after the upstream title, in snake_case, with the `describe` title in front: `test('should support pseudo element')` in `test.describe('toHaveCSS')` becomes `test_to_have_css_should_support_pseudo_element`.
+- Add the sync mirror in `tests/sync/`, with the same file name and test name.
+
+**Second rule: keep the number of tests small.** This applies to every test, and most of all to Python-only behavior that has no upstream test (the sync API, asyncio, the driver).
+
+- **Extend before you add**: before you write a new test, look for an existing test that covers the same feature or code path. If one exists, add the new edge case or assertion to it. Create a new test only when no existing test is a good fit, or when the new scenario needs a different setup.
+- **New features**: cover the mainstream scenario and the important edge cases only. Do not create matrices of tests for every scenario, option, or aspect.
+- **Regressions**: generalize the provided regression cases into meaningful tests, and stop there. Do not add more tests around them.
+
 ## Rolling Playwright to a new version
 
 This is the recurring high-stakes task. Use the dedicated skill:

playwright/_impl/_assertions.py

@@ -505,9 +505,10 @@ async def not_to_have_css(
         name: str,
         value: Union[str, Pattern[str]],
         timeout: float = None,
+        pseudo: Literal["after", "before"] = None,
     ) -> None:
         __tracebackhide__ = True
-        await self._not.to_have_css(name, value, timeout)
+        await self._not.to_have_css(name, value, timeout, pseudo)
 
     async def to_have_id(
         self,

playwright/async_api/_generated.py

@@ -14112,6 +14112,7 @@ async def not_to_have_css(
         name: str,
         value: typing.Union[str, typing.Pattern[str]],
         *,
+        pseudo: typing.Optional[Literal["after", "before"]] = None,
         timeout: typing.Optional[typing.Union[float, datetime.timedelta]] = None,
     ) -> None:
         """LocatorAssertions.not_to_have_css
@@ -14124,13 +14125,15 @@ async def not_to_have_css(
             CSS property name.
         value : Union[Pattern[str], str]
             CSS property value.
+        pseudo : Union["after", "before", None]
+            Pseudo-element to read computed styles from.
         timeout : Union[float, None]
             Time to retry the assertion for in milliseconds. Defaults to `5000`.
         """
         __tracebackhide__ = True
 
         await self._impl_obj.not_to_have_css(
-            name=name, value=value, timeout=to_milliseconds(timeout)
+            name=name, value=value, pseudo=pseudo, timeout=to_milliseconds(timeout)
         )
 
     async def not_to_have_id(

playwright/sync_api/_generated.py

@@ -14184,6 +14184,7 @@ def not_to_have_css(
         name: str,
         value: typing.Union[str, typing.Pattern[str]],
         *,
+        pseudo: typing.Optional[Literal["after", "before"]] = None,
         timeout: typing.Optional[typing.Union[float, datetime.timedelta]] = None,
     ) -> None:
         """LocatorAssertions.not_to_have_css
@@ -14196,14 +14197,16 @@ def not_to_have_css(
             CSS property name.
         value : Union[Pattern[str], str]
             CSS property value.
+        pseudo : Union["after", "before", None]
+            Pseudo-element to read computed styles from.
         timeout : Union[float, None]
             Time to retry the assertion for in milliseconds. Defaults to `5000`.
         """
         __tracebackhide__ = True
 
         self._sync(
             self._impl_obj.not_to_have_css(
-                name=name, value=value, timeout=to_milliseconds(timeout)
+                name=name, value=value, pseudo=pseudo, timeout=to_milliseconds(timeout)
             )
         )
 

tests/async/test_expect_misc.py

@@ -78,3 +78,23 @@ async def test_should_have_timeout_error_name(page: Page) -> None:
     with pytest.raises(TimeoutError) as exc_info:
         await page.wait_for_selector("#not-found", timeout=1)
     assert exc_info.value.name == "TimeoutError"
+
+
+async def test_to_have_css_should_support_pseudo_element(page: Page) -> None:
+    await page.set_content(
+        """
+      <style>
+        #node::before {
+          color: rgb(255, 0, 0);
+          content: "Text content";
+        }
+      </style>
+      <div id=node></div>
+    """
+    )
+    locator = page.locator("#node")
+    await expect(locator).to_have_css("color", "rgb(255, 0, 0)", pseudo="before")
+    with pytest.raises(AssertionError):
+        await expect(locator).not_to_have_css(
+            "color", "rgb(255, 0, 0)", pseudo="before", timeout=100
+        )

tests/sync/test_expect_misc.py

@@ -70,3 +70,23 @@ def test_to_be_in_viewport_should_report_intersection_even_if_fully_covered_by_o
     """
     )
     expect(page.locator("h1")).to_be_in_viewport()
+
+
+def test_to_have_css_should_support_pseudo_element(page: Page) -> None:
+    page.set_content(
+        """
+      <style>
+        #node::before {
+          color: rgb(255, 0, 0);
+          content: "Text content";
+        }
+      </style>
+      <div id=node></div>
+    """
+    )
+    locator = page.locator("#node")
+    expect(locator).to_have_css("color", "rgb(255, 0, 0)", pseudo="before")
+    with pytest.raises(AssertionError):
+        expect(locator).not_to_have_css(
+            "color", "rgb(255, 0, 0)", pseudo="before", timeout=100
+        )