Add WebDriver tests for computed label/role

This adds tests for the new Get Computed Role and
Get Computed Label endpoints
described in w3c/webdriver#1444

webdriver/tests/get_computed_label/get.py

@@ -0,0 +1,35 @@
+import pytest
+from six import text_type
+
+from webdriver.error import NoSuchAlertException
+
+from tests.support.asserts import assert_error, assert_success
+from tests.support.inline import inline
+
+
+def get_computed_label(session, element):
+    return session.transport.send(
+        "GET", "session/{session_id}/element/{element_id}/computedlabel".format(
+            session_id=session.session_id,
+            element_id=element))
+
+
+def test_no_browsing_context(session, closed_window):
+    response = get_computed_label(session)
+    assert_error(response, "no such window")
+
+
+def test_no_user_prompt(session):
+    response = get_computed_label(session)
+    assert_error(response, "no such alert")
+
+
+@pytest.mark.parametrize("tag,label", [
+    ("<button>ok</button>", "ok"),
+    ("<button aria-labelledby='one two'></button><div id='one'>ok</div><div id='two'>go</div>", "ok go"),
+    ("<button aria-label='foo'>bar</button>", "foo")]
+def test_get_computed_label(session, tag, label):
+    session.url=inline("{0}".format(tag))
+    element=session.find.css(tag, all=False)
+    result=get_computed_label(session, element.id)
+    assert_success(result, label)

webdriver/tests/get_computed_role/get.py

@@ -0,0 +1,35 @@
+import pytest
+from six import text_type
+
+from webdriver.error import NoSuchAlertException
+
+from tests.support.asserts import assert_error, assert_success
+from tests.support.inline import inline
+
+
+def get_computed_role(session, element):
+    return session.transport.send(
+        "GET", "session/{session_id}/element/{element_id}/computedrole".format(
+            session_id=session.session_id,
+            element_id=element))
+
+
+def test_no_browsing_context(session, closed_window):
+    response = get_computed_role(session, "id")
+    assert_error(response, "no such window")
+
+
+def test_no_user_prompt(session):
+    response = get_computed_role(session, "id")
+    assert_error(response, "no such alert")
+
+
+@pytest.mark.parametrize("tag,role", [
+    ("li", "menuitem"),
+    ("input", "searchbox"),
+    ("img", "presentation")])
+def test_computed_roles(session, tag, role):
+    session.url = inline("<{0} role={1}>".format(tag, role))
+    element = session.find.css(tag, all=False)
+    result = get_computed_role(session, element.id)
+    assert_success(result, role)