Polished.
Added a test based on a user-forum question.
Modified the test so that it better matches to the given use-case by the user-forum.
Extended the test to show the user how to properly make use of the Spring PropertyPlaceholderConfigurer.SYSTEM_PROPERTIES_XYZ setting.
Put back the line feed being unintentionally removed by the previous commit.
Polished the comment of the tests being recently added into the codebase.