The test

 Scenario: Management interface is secured and JAVA_OPTS is modified
    When container is started with env
       | variable                    | value             |
       | ADMIN_USERNAME          | admin2            |
       | ADMIN_PASSWORD          | lollerskates11$   |
       | JAVA_OPTS_APPEND            | -Dfoo=bar         |
    Then container log should contain WFLYSRV0025
     And run /opt/eap/bin/jboss-cli.sh -c --error-on-interact --no-local-auth --user=admin2 --password=lollerskates11$ deployment-info in container once
     # We expect this command to fail, so make sure the return code is zero, we're interested only in output here
     And run /opt/eap/bin/jboss-cli.sh -c --error-on-interact --no-local-auth deployment-info || true in container and immediately check its output does not contain activemq-rar
     And container log should contain -Dfoo=bar

should be failing, as in the current EAP7 image, the management port is not secured even when ADMIN_USERNAME / ADMIN_PASSWORD is set.

The test however passes, as can be seen in the log

2017-06-28 06:41:04,451 - ctf.steps.container - INFO - Preparing to execute '/opt/eap/bin/jboss-cli.sh -c --error-on-interact --no-local-auth deployment-info || true' command in 'Management interface is secured and JAVA_OPTS is modified' container
2017-06-28 06:41:04,451 - ctf.steps.container - INFO - Executing command just once...
And run /opt/eap/bin/jboss-cli.sh -c --error-on-interact --no-local-auth deployment-info || true in container and immediately check its output does not contain activemq-rar # steps/container_steps.py:180
2017-06-28 06:41:05,324 - ctf.steps.container - DEBUG - Return code: 1, captured execute output: Picked up JAVA_TOOL_OPTIONS: -Duser.home=/home/jboss -Duser.name=jboss
'||' is assumed to be a command(s) but the commands to execute have been specified by another argument: [deployment-info]

And container log should contain -Dfoo=bar # steps/container_steps.py:23
2017-06-28 06:41:05,351 - root - INFO - Message '-Dfoo=bar' was found in the logs

because of the "||' is assumed...", the command does return 1 , thus so it throws an exception, thus

@then(u'run {cmd} in container and immediately check its output does not contain {output_phrase}')
def run_command_immediately_unexpect_message(context, cmd, output_phrase):
    try:
        run_command_expect_message(context, cmd, output_phrase, 0)
    except:
        return True

returns True