[wdspec] Run each "Send Alert Text" in its own tab.

To prevent possible rate limits by the browser when running the
tests in verify mode, each test should run in its own tab.

Differential Revision: https://phabricator.services.mozilla.com/D20312

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1528463
gecko-commit: 83a92a1a4986eaccd94bb16e9b38b41aa1ab445e
gecko-integration-branch: autoland
gecko-reviewers: jgraham

webdriver/tests/send_alert_text/conftest.py

@@ -0,0 +1,24 @@
+import pytest
+
+from webdriver.error import NoSuchAlertException, NoSuchWindowException
+
+
+@pytest.fixture(name="session")
+def fixture_session(capabilities, session, create_window):
+    """Prevent dialog rate limits by running the test in a new window."""
+    original_handle = session.window_handle
+    session.window_handle = create_window()
+
+    yield session
+
+    try:
+        session.alert.dismiss()
+    except NoSuchAlertException:
+        pass
+
+    try:
+        session.close()
+    except NoSuchWindowException:
+        pass
+
+    session.window_handle = original_handle