https://tracker.moodle.org/browse/MDL-61063 
BEHAT RESULTS:
$vendor/bin/behat --config /Volumes/HDDATA/dev/private/bht_moodledata35/behatrun/behat/behat.yml --name="Clear scheduled task fail delay" --format=pretty --out=/pretty.txt

@tool @tool_task
Feature: Clear scheduled task fail delay
  In order to stop failures from delaying a scheduled task run
  As an admin
  I need to be able to clear the fail delay on a task

  Background:                                                                                           # /Volumes/HDDATA/dev/htdocsnew/moodle35/admin/tool/task/tests/behat/clear_fail_delay.feature:7
    Given the scheduled task "\core\task\send_new_user_passwords_task" has a fail delay of "60" seconds # behat_hooks::i_look_for_exceptions()
    And I log in as "admin"                                                                             # behat_hooks::i_look_for_exceptions()
    And I navigate to "Scheduled tasks" node in "Site administration > Server"                          # behat_hooks::i_look_for_exceptions()

  Scenario: Clear fail delay                                                    # /Volumes/HDDATA/dev/htdocsnew/moodle35/admin/tool/task/tests/behat/clear_fail_delay.feature:12
    When I click on "Clear" "text" in the "Send new user passwords" "table_row" # behat_hooks::i_look_for_exceptions()
    And I should see "Are you sure you want to clear the fail delay"            # behat_hooks::i_look_for_exceptions()
    And I press "Clear"                                                         # behat_hooks::i_look_for_exceptions()
    Then I should not see "60" in the "Send new user passwords" "table_row"     # behat_hooks::i_look_for_exceptions()
    And I should not see "Clear" in the "Send new user passwords" "table_row"   # behat_hooks::i_look_for_exceptions()

  Scenario: Cancel clearing the fail delay                                      # /Volumes/HDDATA/dev/htdocsnew/moodle35/admin/tool/task/tests/behat/clear_fail_delay.feature:20
    When I click on "Clear" "text" in the "Send new user passwords" "table_row" # behat_hooks::i_look_for_exceptions()
    And I press "Cancel"                                                        # behat_hooks::i_look_for_exceptions()
    Then I should see "60" in the "Send new user passwords" "table_row"         # behat_hooks::i_look_for_exceptions()
    And I should see "Clear" in the "Send new user passwords" "table_row"       # behat_hooks::i_look_for_exceptions()

2 escenarios (2 pasaron)
15 pasos (15 pasaron)
0m14.69s (43.00Mb)

PHPUNIT RESULTS
---------------
$vendor/bin/phpunit lib/tests/scheduled_task_test.php 
Moodle 3.5dev (Build: 20171214)
Php: 7.0.25, mysqli: 5.5.44, OS: Darwin 15.2.0 x86_64
PHPUnit 6.4.4 by Sebastian Bergmann and contributors.

..........                                                        10 / 10 (100%)

Time: 1.17 minutes, Memory: 36.00MB

OK (10 tests, 66 assertions)