Check stderrs

examples/html.feature

@@ -2,7 +2,7 @@ Feature: HTML
   Scenario: Check an empty HTML file
     Given a file named "foo.html" with ""
     When I successfully run `liche foo.html`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Check a HTML file
     Given a file named "foo.html" with:
@@ -21,4 +21,4 @@ Feature: HTML
     </html>
     """
     When I successfully run `liche foo.html`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""

examples/markdown.feature

@@ -2,7 +2,7 @@ Feature: Markdown
   Scenario: Check an empty markdown file
     Given a file named "foo.md" with ""
     When I successfully run `liche foo.md`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Check a markdown file
     Given a file named "foo.md" with:
@@ -23,7 +23,7 @@ Feature: Markdown
     ```
     """
     When I successfully run `liche foo.md`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Check a markdown file which contains a live link
     Given a file named "foo.md" with:
@@ -31,7 +31,7 @@ Feature: Markdown
     [Google](https://google.com)
     """
     When I successfully run `liche foo.md`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Check a markdown file which contains a dead link
     Given a file named "foo.md" with:
@@ -63,7 +63,7 @@ Feature: Markdown
     [Yahoo](https://yahoo.com)
     """
     When I successfully run `liche foo.md bar.md`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Check images and links
     Given a file named "foo.md" with:

examples/options.feature

@@ -32,7 +32,7 @@ Feature: Options
     [Google](https://google.com)
     """
     When I successfully run `liche --timeout 10 foo.md`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Set concurrency
     Given a file named "foo.md" with:
@@ -40,7 +40,7 @@ Feature: Options
     [Google](https://google.com)
     """
     When I successfully run `liche --concurrency 10 foo.md`
-    Then the stdout should contain exactly ""
+    Then the stderr should contain exactly ""
 
   Scenario: Search files recursively
     Given a directory named "foo"