undefined steps always fail the test run

resolves #867

CHANGELOG.md

@@ -8,6 +8,7 @@
 * `cucumber-expressions`:
   * using an undefined parameter type now results in an error
   * `{stringInDoubleQuotes}` is now `{string}` which works for strings in single or double quotes
+* Undefined steps fail the build in non-strict mode. Non-strict mode only allows pending steps now.
 
 #### New Features
 

features/strict_mode.feature

@@ -1,7 +1,7 @@
 Feature: Strict mode
 
   Using the `--no-strict` flag will cause cucumber to succeed even if there are
-  undefined or pending steps.
+  pending steps.
 
   Background:
     Given a file named "features/a.feature" with:
@@ -11,14 +11,6 @@ Feature: Strict mode
           Given a step
       """
 
-  Scenario: Fail with undefined step by default
-    When I run cucumber.js
-    Then it fails
-
-  Scenario: Succeed with undefined step with --no-strict
-    When I run cucumber.js with `--no-strict`
-    Then it passes
-
   Scenario: Fail with pending step by default
     Given a file named "features/step_definitions/cucumber_steps.js" with:
       """

src/runtime/index.js

@@ -76,9 +76,8 @@ export default class Runtime {
 
   shouldCauseFailure(status) {
     return (
-      _.includes([Status.AMBIGUOUS, Status.FAILED], status) ||
-      (_.includes([Status.PENDING, Status.UNDEFINED], status) &&
-        this.options.strict)
+      _.includes([Status.AMBIGUOUS, Status.FAILED, Status.UNDEFINED], status) ||
+      (status === Status.PENDING && this.options.strict)
     )
   }
 }