diff --git a/src/testdir/test_findfile.vim b/src/testdir/test_findfile.vim
index f8be713..3a1066b 100644
--- a/src/testdir/test_findfile.vim
+++ b/src/testdir/test_findfile.vim
@@ -294,7 +294,6 @@
   " basic tests
   func FindExpr1()
     let fnames = ['Xfindexpr1.c', 'Xfindexpr2.c', 'Xfindexpr3.c']
-    "return fnames->copy()->filter('v:val =~? v:fname')->join("\n")
     return fnames->copy()->filter('v:val =~? v:fname')
   endfunc
 
@@ -353,8 +352,8 @@
   set findexpr=FindExpr2()
   call assert_fails('find Xfindexpr1.c', 'find error')
 
-  " Try using a null string as the expression
-  set findexpr=test_null_string()
+  " Try using a null List as the expression
+  set findexpr=test_null_list()
   call assert_fails('find Xfindexpr1.c', 'E345: Can''t find file "Xfindexpr1.c" in path')
 
   " Try to create a new window from the find expression
@@ -373,6 +372,10 @@
   set findexpr=FindExpr4()
   call assert_fails('find Xfindexpr1.c', 'E565: Not allowed to change text or change window')
 
+  " Expression returning a string
+  set findexpr='abc'
+  call assert_fails('find Xfindexpr1.c', 'E1514: findexpr did not return a List type')
+
   set findexpr&
   delfunc! FindExpr1
   delfunc! FindExpr2
@@ -449,4 +452,31 @@
   delfunc s:FindExprScript
 endfunc
 
+" Test for expanding the argument to the :find command using 'findexpr'
+func Test_findexpr_expand_arg()
+  func FindExpr1()
+    let fnames = ['Xfindexpr1.c', 'Xfindexpr2.c', 'Xfindexpr3.c']
+    return fnames->copy()->filter('v:val =~? v:fname')
+  endfunc
+  set findexpr=FindExpr1()
+
+  call feedkeys(":find \<Tab>\<C-B>\"\<CR>", "xt")
+  call assert_equal('"find Xfindexpr1.c', @:)
+
+  call feedkeys(":find Xfind\<Tab>\<Tab>\<C-B>\"\<CR>", "xt")
+  call assert_equal('"find Xfindexpr2.c', @:)
+
+  call feedkeys(":find *3*\<Tab>\<C-B>\"\<CR>", "xt")
+  call assert_equal('"find Xfindexpr3.c', @:)
+
+  call feedkeys(":find Xfind\<C-A>\<C-B>\"\<CR>", "xt")
+  call assert_equal('"find Xfindexpr1.c Xfindexpr2.c Xfindexpr3.c', @:)
+
+  call feedkeys(":find abc\<Tab>\<C-B>\"\<CR>", "xt")
+  call assert_equal('"find abc', @:)
+
+  set findexpr&
+  delfunc! FindExpr1
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab