Update

autoload/rust.vim

@@ -1,6 +1,5 @@
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'rust') == -1
 
-" Author: Kevin Ballard
 " Description: Helper functions for Rust commands/mappings
 " Last Modified: May 27, 2014
 " For bugs, patches and license go to https://github.com/rust-lang/rust.vim
@@ -510,16 +509,23 @@ function! s:SearchTestFunctionNameUnderCursor() abort
     return matchstr(getline(test_func_line), '\m\C^\s*fn\s\+\zs\h\w*')
 endfunction
 
-function! rust#Test(all, options) abort
+function! rust#Test(mods, winsize, all, options) abort
     let manifest = findfile('Cargo.toml', expand('%:p:h') . ';')
     if manifest ==# ''
         return rust#Run(1, '--test ' . a:options)
     endif
 
+    " <count> defaults to 0, but we prefer an empty string
+    let winsize = a:winsize ? a:winsize : ''
+
     if has('terminal')
-        let cmd = 'terminal '
+        if has('patch-8.0.910')
+            let cmd = printf('%s noautocmd %snew | terminal ++curwin ', a:mods, winsize)
+        else
+            let cmd = printf('%s terminal ', a:mods)
+        endif
     elseif has('nvim')
-        let cmd = 'noautocmd new | terminal '
+        let cmd = printf('%s noautocmd %snew | terminal ', a:mods, winsize)
     else
         let cmd = '!'
         let manifest = shellescape(manifest)