--- a/testing/web-platform/meta/MANIFEST.json
+++ b/testing/web-platform/meta/MANIFEST.json
@@ -405128,16 +405128,24 @@
     ]
    ],
    "webdriver/tests/element_click/select.py": [
     [
      "/webdriver/tests/element_click/select.py",
      {}
     ]
    ],
+   "webdriver/tests/fullscreen_window.py": [
+    [
+     "/webdriver/tests/fullscreen_window.py",
+     {
+      "timeout": "long"
+     }
+    ]
+   ],
    "webdriver/tests/get_window_rect.py": [
     [
      "/webdriver/tests/get_window_rect.py",
      {}
     ]
    ],
    "webdriver/tests/maximize_window.py": [
     [
@@ -624316,17 +624324,17 @@
    "55100f7d505bc8cbc966ced0d1337ed78534a553",
    "testharness"
   ],
   "web-animations/animation-model/animation-types/property-list.js": [
    "31ad7b4aa12e4485f95545b087779cabb56c696c",
    "support"
   ],
   "web-animations/animation-model/animation-types/property-types.js": [
-   "80be6cea9cc4d5986abbdf2823e013b8e5b4bcab",
+   "f7947653d8668f236117913217d808e690476059",
    "support"
   ],
   "web-animations/animation-model/combining-effects/effect-composition.html": [
    "8ac06085132d822e908d48de4c1109b66323f19f",
    "testharness"
   ],
   "web-animations/animation-model/keyframe-effects/effect-value-context.html": [
    "10d9ee521240475a1729c2facfcea8b50342614e",
@@ -625071,16 +625079,20 @@
   "webdriver/tests/element_click/__init__.py": [
    "da39a3ee5e6b4b0d3255bfef95601890afd80709",
    "support"
   ],
   "webdriver/tests/element_click/select.py": [
    "5ba51b660c7203bba3ada597c2f56fe094358e1f",
    "wdspec"
   ],
+  "webdriver/tests/fullscreen_window.py": [
+   "4c29502fdb33983664fcc687ea87ddac66f36f08",
+   "wdspec"
+  ],
   "webdriver/tests/get_window_rect.py": [
    "2d4c13edc4e659af864750d0341c06ff969a687f",
    "wdspec"
   ],
   "webdriver/tests/maximize_window.py": [
    "55cb76c60c7914bc024f470f6d1f0a47294b6fe3",
    "wdspec"
   ],

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/meta/webdriver/tests/fullscreen_window.py.ini
@@ -0,0 +1,7 @@
+[fullscreen_window.py]
+  type: wdspec
+  [fullscreen_window.py::test_handle_prompt_accept]
+    expected: FAIL
+
+  [fullscreen_window.py::test_handle_prompt_missing_value]
+    expected: FAIL

--- a/testing/web-platform/meta/webdriver/tests/set_window_rect.py.ini
+++ b/testing/web-platform/meta/webdriver/tests/set_window_rect.py.ini
@@ -1,10 +1,7 @@
 [set_window_rect.py]
   type: wdspec
   [set_window_rect.py::test_prompt_accept]
     expected: FAIL
 
   [set_window_rect.py::test_handle_prompt_missing_value]
     expected: FAIL
-
-  [set_window_rect.py::test_fullscreened]
-    expected: FAIL

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/tests/webdriver/tests/fullscreen_window.py
@@ -0,0 +1,198 @@
+# META: timeout=long
+
+from tests.support.inline import inline
+from tests.support.asserts import assert_error, assert_success, assert_dialog_handled
+from tests.support.fixtures import create_dialog
+
+
+alert_doc = inline("<script>window.alert()</script>")
+
+
+def read_global(session, name):
+    return session.execute_script("return %s;" % name)
+
+
+def fullscreen(session):
+    return session.transport.send("POST", "session/%s/window/fullscreen" % session.session_id)
+
+
+# 10.7.5 Fullscreen Window
+
+
+# 1. If the current top-level browsing context is no longer open, return error
+#    with error code no such window.
+def test_no_browsing_context(session, create_window):
+    # step 1
+    session.window_handle = create_window()
+    session.close()
+    response = fullscreen(session)
+    assert_error(response, "no such window")
+
+
+# [...]
+# 2. Handle any user prompts and return its value if it is an error.
+# [...]
+# In order to handle any user prompts a remote end must take the following
+# steps:
+# 2. Run the substeps of the first matching user prompt handler:
+#
+#    [...]
+#    - accept state
+#      1. Accept the current user prompt.
+#    [...]
+#
+# 3. Return success.
+def test_handle_prompt_accept(new_session):
+    _, session = new_session({"alwaysMatch": {"unhandledPromptBehavior": "accept"}})
+    session.url = inline("<title>WD doc title</title>")
+    create_dialog(session)("alert", text="accept #1", result_var="accept1")
+
+    expected_title = read_global(session, "document.title")
+    response = fullscreen(session)
+
+    assert_success(response, expected_title)
+    assert_dialog_handled(session, "accept #1")
+    assert read_global(session, "accept1") == None
+
+    expected_title = read_global(session, "document.title")
+    create_dialog(session)("confirm", text="accept #2", result_var="accept2")
+
+    response = fullscreen(session)
+
+    assert_success(response, expected_title)
+    assert_dialog_handled(session, "accept #2")
+    assert read_global(session, "accept2"), True
+
+    expected_title = read_global(session, "document.title")
+    create_dialog(session)("prompt", text="accept #3", result_var="accept3")
+
+    response = fullscreen(session)
+
+    assert_success(response, expected_title)
+    assert_dialog_handled(session, "accept #3")
+    assert read_global(session, "accept3") == ""
+
+
+# [...]
+# 2. Handle any user prompts and return its value if it is an error.
+# [...]
+# In order to handle any user prompts a remote end must take the following
+# steps:
+# 2. Run the substeps of the first matching user prompt handler:
+#
+#    [...]
+#    - missing value default state
+#    - not in the table of simple dialogs
+#      1. Dismiss the current user prompt.
+#      2. Return error with error code unexpected alert open.
+def test_handle_prompt_missing_value(session, create_dialog):
+    session.url = inline("<title>WD doc title</title>")
+    create_dialog("alert", text="dismiss #1", result_var="dismiss1")
+
+    response = fullscreen(session)
+
+    assert_error(response, "unexpected alert open")
+    assert_dialog_handled(session, "dismiss #1")
+    assert read_global(session, "accept1") == None
+
+    create_dialog("confirm", text="dismiss #2", result_var="dismiss2")
+
+    response = fullscreen(session)
+
+    assert_error(response, "unexpected alert open")
+    assert_dialog_handled(session, "dismiss #2")
+    assert read_global(session, "dismiss2") == False
+
+    create_dialog("prompt", text="dismiss #3", result_var="dismiss3")
+
+    response = fullscreen(session)
+
+    assert_error(response, "unexpected alert open")
+    assert_dialog_handled(session, "dismiss #3")
+    assert read_global(session, "dismiss3") == None
+
+
+# 4. Call fullscreen an element with the current top-level browsing
+# context's active document's document element.
+def test_fullscreen(session):
+    # step 4
+    response = fullscreen(session)
+    assert_success(response)
+    assert session.execute_script("return window.fullScreen") == True
+
+
+# 5. Return success with the JSON serialization of the current top-level
+# browsing context's window rect.
+#
+# [...]
+#
+# A top-level browsing context's window rect is defined as a
+# dictionary of the screenX, screenY, width and height attributes of the
+# WindowProxy. Its JSON representation is the following:
+#
+#   x
+#     WindowProxy's screenX attribute.
+#
+#   y
+#     WindowProxy's screenY attribute.
+#
+#   width
+#     Width of the top-level browsing context's outer dimensions,
+#     including any browser chrome and externally drawn window
+#     decorations in CSS reference pixels.
+#
+#   height
+#     Height of the top-level browsing context's outer dimensions,
+#     including any browser chrome and externally drawn window decorations
+#     in CSS reference pixels.
+#
+#   state
+#     The top-level browsing context's window state.
+#
+# [...]
+#
+# The top-level browsing context has an associated window state which
+# describes what visibility state its OS widget window is in. It can be
+# in one of the following states:
+#
+#   "maximized"
+#     The window is maximized.
+#
+#   "minimized"
+#     The window is iconified.
+#
+#   "normal"
+#     The window is shown normally.
+#
+#   "fullscreen"
+#     The window is in full screen mode.
+#
+# If for whatever reason the top-level browsing context's OS window
+# cannot enter either of the window states, or if this concept is not
+# applicable on the current system, the default state must be normal.
+def test_payload(session):
+    response = fullscreen(session)
+
+    # step 5
+    assert response.status == 200
+    assert isinstance(response.body["value"], dict)
+
+    rect = response.body["value"]
+    assert "width" in rect
+    assert "height" in rect
+    assert "x" in rect
+    assert "y" in rect
+    assert isinstance(rect["width"], (int, float))
+    assert isinstance(rect["height"], (int, float))
+    assert isinstance(rect["x"], (int, float))
+    assert isinstance(rect["y"], (int, float))
+
+
+def test_exit_fullscreen_on_second_call(session):
+    first_response = fullscreen(session)
+    assert_success(first_response)
+    assert session.execute_script("return window.fullScreen") == True
+
+    second_response = fullscreen(session)
+    assert_success(second_response)
+    assert session.execute_script("return window.fullScreen") == False