Use assert_nil to fix warnings

test/unit/error_collector_test.rb

@@ -156,10 +156,10 @@ def test_can_handle_explicit_null_error_values
       assert_equal "1337", error.id
 
       assert_equal({}, error.about, nil)
-      assert_equal(nil, error.status, nil)
-      assert_equal(nil, error.code, nil)
-      assert_equal(nil, error.title, nil)
-      assert_equal(nil, error.detail, nil)
+      assert_nil(error.status, nil)
+      assert_nil(error.code, nil)
+      assert_nil(error.title, nil)
+      assert_nil(error.detail, nil)
       assert_equal({}, error.source, nil)
       assert_equal({}, error.meta.attributes,nil)
   end

test/unit/parser_test.rb

@@ -53,7 +53,7 @@ def test_can_parse_null_data
     article = Article.find(1).first
     author = article.author
 
-    assert_equal nil, author
+    assert_nil author
   end
 
 end

test/unit/schemable_test.rb

@@ -56,8 +56,8 @@ def test_defines_defaults
     assert_equal 'foo', resource['a']
     assert_equal false, resource.b
     assert_equal false, resource['b']
-    assert_equal nil, resource.c
-    assert_equal nil, resource.d
+    assert_nil resource.c
+    assert_nil resource.d
   end
 
   def test_find_property_definition
@@ -90,7 +90,7 @@ def test_can_define_multiple_properties
 
     MultipleSchema.schema.each_property do |property|
       assert_equal :string, property.type
-      assert_equal nil, property.default
+      assert_nil property.default
     end
   end
 

test/unit/top_level_links_test.rb

@@ -253,7 +253,7 @@ def assert_pagination_when_no_next_page
     assert_equal 0, articles.offset
     assert_equal 1, articles.total_entries
     assert_equal 1, articles.limit_value
-    assert_equal nil, articles.next_page
+    assert_nil articles.next_page
     assert_equal 1, articles.per_page
     assert_equal false, articles.out_of_bounds?