Update

compiler/exunit.vim

@@ -16,9 +16,15 @@ endif
 
 let s:cpo_save = &cpo
 set cpo-=C
-
 CompilerSet makeprg=mix\ test
-CompilerSet errorformat=%A\ \ %.)\ %m(%.%#),%C\ \ \ \ \ **%m,%C\ \ \ \ \ \ \ %m,%Z\ \ \ \ \ at\ %f:%l,%-G%.%#
+CompilerSet errorformat=
+  \%E\ \ %n)\ %m,
+  \%+G\ \ \ \ \ **\ %m,
+  \%+G\ \ \ \ \ stacktrace:,
+  \%C\ \ \ \ \ %f:%l,
+  \%+G\ \ \ \ \ \ \ (%\\w%\\+)\ %f:%l:\ %m,
+  \%+G\ \ \ \ \ \ \ %f:%l:\ %.%#,
+  \**\ (%\\w%\\+)\ %f:%l:\ %m
 
 let &cpo = s:cpo_save
 unlet s:cpo_save

compiler/rspec.vim

@@ -27,6 +27,7 @@ CompilerSet errorformat=
     \%-Z\ \ \ \ \ %\\+\#\ %f:%l:%.%#,
     \%E\ \ %\\d%\\+)%.%#,
     \%C\ \ \ \ \ %m,
+    \%C%\\s%#,
     \%-G%.%#
 
 let &cpo = s:cpo_save