You have a Scenario or Scenario Outline without a Then step. You should add a Then step to show what the scenario is testing.

Bad

Feature: logging in

  Scenario: logging in
    Given I have visited the website
    When I log in with "<username>" and "<password>"

Good

Feature: logging in

  Scenario: logging in
    Given I have visited the website
    When I log in with "<username>" and "<password>"
    Then I will see my account