X_TEST_LOCATOR_EXPECTED
Means
a matcher expected a locator and got something else
Typical cause
toBeVisible handed a page, a selector string, or the result of awaiting the locator — anything with no isVisible(). Thrown rather than returned as a failing result, exactly as X_TEST_SCHEMA_EXPECTED is: the assertion is not false, it is unanswerable, and a pass: false would read as "the element was hidden"
Fix
expect(page.getByRole("heading", { name: "Feed" })).toBeVisible() — the locator itself, unawaited