test: verify that msgpacks-rpc exceptions are working

test/functional/api/vim_spec.lua

@@ -105,4 +105,10 @@ describe('vim_* functions', function()
       eq(nvim('get_windows')[2], nvim('get_current_window'))
     end)
   end)
+
+  it('can throw exceptions', function()
+    local status, err = pcall(nvim, 'get_option', 'invalid-option')
+    eq(false, status)
+    ok(err:match('Invalid option name') ~= nil)
+  end)
 end)