Try and get AppVeyor to run a single test

.appveyor.yml

@@ -26,4 +26,6 @@ install:
   - cd C:\
 
 test_script:
+  - cd C:\projects\ale
   - C:\vim\vim\vim80\vim.exe --version
+  - 'C:\vim\vim\vim80\vim.exe -u test\vimrc "+Vader! test/test_path_uri.vader"'

test/vimrc

@@ -1,17 +1,25 @@
 " vint: -ProhibitSetNoCompatible
 
-" Make most tests just set lists synchronously when run in Docker.
+" Make most tests just set lists synchronously when run in Docker, etc.
 let g:ale_set_lists_synchronously = 1
 
 " Load builtin plugins
 " We need this because run_vim.sh sets -i NONE
-set runtimepath=/home/vim,$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after,/testplugin,/vader
+if has('win32')
+    set runtimepath=$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after,C:\vader,C:\projects\ale
+else
+    set runtimepath=/home/vim,$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after,/testplugin,/vader
+endif
 
 " The following is just an example
 filetype plugin indent on
 syntax on
-set shell=/bin/sh
-set shellcmdflag=-c
+
+if !has('win32')
+    set shell=/bin/sh
+    set shellcmdflag=-c
+endif
+
 set nocompatible
 set tabstop=4
 set softtabstop=4