feat: adding mfv_existfolder.sas and tests

tests/viya/mfv_existfolder.test.sas

@@ -0,0 +1,29 @@
+/**
+  @file
+  @brief Testing mfv_existfolder macro function
+
+  <h4> SAS Macros </h4>
+  @li mf_uid.sas
+  @li mfv_existfolder.sas
+  @li mp_assert.sas
+  @li mv_createfolder.sas
+
+**/
+
+options mprint sgen;
+
+%let folder=%mf_uid();
+
+/* create a folder */
+%mv_createfolder(path=&mcTestAppLoc/temp/&folder)
+
+
+%mp_assert(
+  iftrue=(%mfv_existfolder(&mcTestAppLoc/temp/&folder)=1),
+  desc=Check if created folder exists
+)
+
+%mp_assert(
+  iftrue=(%mfv_existfolder(&mcTestAppLoc/temp/&folder/%mf_uid()/noway)=0),
+  desc=Check if non created folder does not exist
+)