commit 07e4a197953d12902fb97beb48830a5323a52280
author Bram Moolenaar <Bram@vim.org> Tue Nov 26 12:23:30 2019 +0100
committer Bram Moolenaar <Bram@vim.org> Tue Nov 26 12:23:30 2019 +0100
tree 2606081e24020a6d9985531651099b0fc2aa3381
parent 06b0b4bc27077013e9b4b48fd1d9b33e543ccf99

patch 8.1.2343: using time() for srand() is not very random

Problem:    Using time() for srand() is not very random.
Solution:   use /dev/urandom if available

src/testdir/test_random.vim

diff --git a/src/testdir/test_random.vim b/src/testdir/test_random.vim
index 381475a..9fe71a9 100644
--- a/src/testdir/test_random.vim
+++ b/src/testdir/test_random.vim
@@ -11,9 +11,15 @@
 
   call test_settime(12341234)
   let s = srand()
-  call assert_equal(s, srand())
-  call test_settime(12341235)
-  call assert_notequal(s, srand())
+  if filereadable('/dev/urandom')
+    " using /dev/urandom
+    call assert_notequal(s, srand())
+  else
+    " using time()
+    call assert_equal(s, srand())
+    call test_settime(12341235)
+    call assert_notequal(s, srand())
+  endif
 
   call srand()
   let v = rand()
@@ -25,4 +31,6 @@
   call assert_fails('echo rand([1, [2], 3, 4])', 'E475:')
   call assert_fails('echo rand([1, 2, [3], 4])', 'E475:')
   call assert_fails('echo rand([1, 2, 3, [4]])', 'E475:')
+
+  call test_settime(0)
 endfunc