Apply suggestions from code review

Better namings for unit test cases.

logstash-core/spec/logstash/util/substitution_variables_spec.rb

@@ -37,7 +37,7 @@
 
   describe "exclude config comments" do
 
-    it "doesn't exclude comments if config string dosn't contain ${VAR}" do
+    it "uses as it is if config string doesn't contain ${VAR}" do
       single_line_config = "{ sleep { time => 1 } }"
       multiline_config = "stdout {
         codec => rubydebug
@@ -46,7 +46,7 @@
       expect(substitution_var_test_class.exclude_config_comments(multiline_config)).to eq(multiline_config)
     end
 
-    it "removes the line value if commented" do
+    it "removes the config line if commented" do
       config_with_commented_var_line = 'tcp {
           port => 12345
           #"${TCP_PORT}"
@@ -55,7 +55,7 @@
         .to eq("tcp {\nport => 12345\n}")
     end
 
-    it "wipes out comments if config string contains ${VAR}" do
+    it "wipes out comments if ${VAR} is in the comment of the config string" do
       config_with_var_and_comment = 'elasticsearch {
       	hosts => ["${ES_DEV_HOST}"] # use ["${ES_PROD_HOST}"] for production
         index => "%{[some_field][sub_field]}-%{+YYYY.MM.dd}"