use refute in place of assert ! in test suite (PR #2336)

- replace assert ! with refute
- use assert_nil and refute_nil
- use assert_empty and refute_empty
- use assert_kind_of instead of direct is_a? call
- use assert_respond_to instead of direct respond_to? call

1 files changed, 4 insertions, 4 deletions

diff --git a/test/parser_test.rb b/test/parser_test.rb
index db7fcce7..2dedf388 100644
--- a/test/parser_test.rb
+++ b/test/parser_test.rb
@@ -606,7 +606,7 @@ v8.6.8,
     metadata, _ = parse_header_metadata input
     assert_equal 7, metadata.size
     assert_equal '8.6.8', metadata['revnumber']
-    assert !metadata.has_key?('revdate')
+    refute metadata.has_key?('revdate')
   end
 
   # Asciidoctor recognizes a standalone revision without a trailing comma
@@ -618,7 +618,7 @@ v8.6.8
     metadata, _ = parse_header_metadata input
     assert_equal 7, metadata.size
     assert_equal '8.6.8', metadata['revnumber']
-    assert !metadata.has_key?('revdate')
+    refute metadata.has_key?('revdate')
   end
 
   # while compliant w/ AsciiDoc, this is just sloppy parsing
@@ -650,7 +650,7 @@ Joe Cool
     EOS
     metadata, _ = parse_header_metadata input
     refute_equal 'page-layout: post', metadata['revremark']
-    assert !metadata.has_key?('revdate')
+    refute metadata.has_key?('revdate')
   end
 
   test "parse rev remark only" do
@@ -660,7 +660,7 @@ Joe Cool
     EOS
     metadata, _ = parse_header_metadata input
     assert_equal 'Must start revremark-only line with space', metadata['revremark']
-    assert !metadata.has_key?('revdate')
+    refute metadata.has_key?('revdate')
   end
 
   test "skip line comments before author" do