Add testing

shared/isWritable.go

@@ -6,6 +6,8 @@ package shared
 import "golang.org/x/sys/unix"
 
 // Copied from https://stackoverflow.com/a/20026945 and https://stackoverflow.com/a/49148866
+// Not testable as host environment could be just about anything
+// and this function is for testing the host environment
 func IsWritable(path string) bool {
 	return unix.Access(path, unix.W_OK) == nil
 }