test(run): Add test for separate output and error

test/bats.bats

@@ -262,3 +262,8 @@ fixtures bats
   [ $status -eq 0 ]
   [ "${lines[1]}" = "ok 1 loop_func" ]
 }
+
+@test "testing stdout and stderr are separated" {
+  run bats "$FIXTURE_ROOT/stdout_stderr_separate.bats"
+  [ $status -eq 0 ]
+}

test/fixtures/bats/stdout_stderr_separate.bats

@@ -0,0 +1,14 @@
+# see issue #89
+echo_std_err() {
+  echo "std output"
+  (>&2 echo "err output")
+  return 0
+}
+
+@test "std err" {
+  run echo_std_err
+  [ $status -eq 0 ]
+  [ "${stdout}" = "std output" ]
+  [ "${stderr}" = "err output" ]
+  [ "${output}" = "std outputerr output" ]
+}