This is a testharness.js-based test.
Harness Error. harness_status.status = 1 , harness_status.message = Uncaught Error: assert_true: Selection should be modified before mouseup event expected true got false
[FAIL] Shift + Primary click should extend the selection
promise_test: Unhandled rejection with value: object "Error: We do not support keydown and keyup mixed with other actions, please use test_driver.send_keys. See crbug.com/893480."
[FAIL] Shift + Primary click in a link shouldn't extend the selection
promise_test: Unhandled rejection with value: object "Error: We do not support keydown and keyup mixed with other actions, please use test_driver.send_keys. See crbug.com/893480."
[FAIL] Primary mouse button down should move caret, and primary mouse button up should extend the selection
assert_equals: Selection#anchorNode should stay in the second <span> element which mousedown occurred on expected Text node "second span." but got Text node "first span."
Harness: the test ran to completion.