diff --git a/bin/cmdtest.rb b/bin/cmdtest.rb
index c3006c0..5587cea 100755
--- a/bin/cmdtest.rb
+++ b/bin/cmdtest.rb
@@ -492,6 +492,10 @@ module Cmdtest
 
     private
 
+    def _sorted_glob(str)
+      Dir.glob(str).sort
+    end
+
     def _fs_test_filenames
       if ! @argv.empty?
         files = _expand_files_or_dirs(@argv)
@@ -502,13 +506,13 @@ module Cmdtest
         return files
       end
 
-      try = Dir.glob("t/CMDTEST_*.rb")
+      try = _sorted_glob("t/CMDTEST_*.rb")
       return try if ! try.empty?
 
-      try = Dir.glob("test/CMDTEST_*.rb")
+      try = _sorted_glob("test/CMDTEST_*.rb")
       return try if ! try.empty?
 
-      try = Dir.glob("CMDTEST_*.rb")
+      try = _sorted_glob("CMDTEST_*.rb")
       return try if ! try.empty?
 
       puts "ERROR: no CMDTEST_*.rb files found"
diff --git a/t/CMDTEST_glob_files.rb b/t/CMDTEST_glob_files.rb
new file mode 100644
index 0000000..73c0f68
--- /dev/null
+++ b/t/CMDTEST_glob_files.rb
@@ -0,0 +1,55 @@
+
+require "selftest_utils"
+
+class CMDTEST_glob_files < Cmdtest::Testcase
+
+  include SelftestUtils
+
+  def make_file(name)
+    create_file "t/CMDTEST_#{name}.rb", [
+      "class CMDTEST_#{name} < Cmdtest::Testcase",
+      "  def setup",
+      "    prepend_path #{BIN.inspect}",
+      "    prepend_path #{PLATFORM_BIN.inspect}",
+      "  end",
+      "",
+
+      "  def test_1",
+      "    cmd \"true\" do",
+      "      comment \"#{name}\"",
+      "    end",
+      "  end",
+      "",
+      "end",
+    ]
+  end
+
+  def test_1
+    make_file("aaa")
+    make_file("ccc")
+    make_file("bbb")
+    make_file("ddd")
+
+    cmd_cmdtest do
+      stdout_equal [
+        "### aaa",
+        "### bbb",
+        "### ccc",
+        "### ddd",
+      ]
+    end
+  end
+
+  def test_2
+    # generate "aaa", "aab", "aac", ...
+    names = (1..30).reduce(["aaa"]) {|acc, i| acc << acc[-1].succ }
+    for name in names.shuffle(random: Random.new(1234))
+      make_file(name)
+    end
+
+    cmd_cmdtest do
+      stdout_equal names.map {|name| "### #{name}" }
+    end
+  end
+
+end