RustTest: specify module name to run exact one test case

Author: rhysd

autoload/rust.vim

@@ -485,6 +485,14 @@ function! rust#Test(all, options) abort
         return
     endif
 
+    let mod_name = expand('%:t:r')
+    if mod_name ==# ''
+        echohl ErrorMsg
+        echo 'Cannot extract a module name from file name. Please add ! to command if you want to run all tests'
+        echohl None
+        return
+    endif
+
     let saved = getpos('.')
     try
         let func_name = s:SearchTestFunctionNameUnderCursor()
@@ -494,10 +502,11 @@ function! rust#Test(all, options) abort
             echohl None
             return
         endif
+        let spec = mod_name . '::' . func_name
         if a:options ==# ''
-            execute cmd . 'cargo test --manifest-path' manifest func_name
+            execute cmd . 'cargo test --manifest-path' manifest spec
         else
-            execute cmd . 'cargo test --manifest-path' manifest func_name a:options
+            execute cmd . 'cargo test --manifest-path' manifest spec a:options
         endif
         return
     finally