+unit tests for null arg handling in WcatTest cstor
+unit test SetsTestResultFilePath
+unit test ReturnsWcatCommandsWrapper
adding File class wrapper and using it in WcatTest; +unit test ReturnsEmptyStringIfNoTestResultFile
adding ReadAllText method to wrapper
+unit test ReturnsResultFileText
fixing unit test ReturnsEmptyStringIfNoTestResultFile
-comment
+unit tests for WcatRunCommand cstor
+unit tests for wcat run command Execute() method; +necessary wrapper classes