Unit testing

Acceptance criteria for the App

Name		Name	Last commit message	Last commit date
Latest commit History 5 Commits
Google_tests		Google_tests
UI		UI
.gitignore		.gitignore
CMakeLists.txt		CMakeLists.txt
Document.cpp		Document.cpp
Document.h		Document.h
HasContent.h		HasContent.h
HasTitle.cpp		HasTitle.cpp
HasTitle.h		HasTitle.h
Invoice.cpp		Invoice.cpp
Invoice.h		Invoice.h
Newspaper.cpp		Newspaper.cpp
Newspaper.h		Newspaper.h
README.md		README.md
WorkWithDocs.cpp		WorkWithDocs.cpp
WorkWithDocs.h		WorkWithDocs.h
WorkWithInheritanceAndVirtualMethods.cpp		WorkWithInheritanceAndVirtualMethods.cpp
WorkWithInheritanceAndVirtualMethods.h		WorkWithInheritanceAndVirtualMethods.h
main.cpp		main.cpp