diff --git a/src/testup/core.rb b/src/testup/core.rb
index 1099e67..7007cc5 100644
--- a/src/testup/core.rb
+++ b/src/testup/core.rb
@@ -1,6 +1,6 @@
 #-------------------------------------------------------------------------------
 #
-# Copyright 2013-2018 Trimble Inc.
+# Copyright 2013-2024 Trimble Inc.
 # License: The MIT License (MIT)
 #
 #-------------------------------------------------------------------------------
@@ -9,7 +9,9 @@
 
 # TODO: Defer this to a point so it doesn't happen during SketchUp startup.
 require 'testup/gem_helper'
-TestUp::GemHelper.require('minitest', 'minitest', version: '5.4.3')
+
+# Minitest 5.15.0 is compatible with Ruby '>= 2.2, < 4.0', released 15-Dec-2021
+TestUp::GemHelper.require('minitest', 'minitest', version: '5.15.0')
 
 require 'testup/ui/runner' if defined?(UI::WebDialog)
 require 'testup/app'
diff --git a/src/testup/file_reporter.rb b/src/testup/file_reporter.rb
index cede48b..6f12e92 100644
--- a/src/testup/file_reporter.rb
+++ b/src/testup/file_reporter.rb
@@ -1,6 +1,6 @@
 #-------------------------------------------------------------------------------
 #
-# Copyright 2013-2016 Trimble Inc.
+# Copyright 2013-2024 Trimble Inc.
 # License: The MIT License (MIT)
 #
 #-------------------------------------------------------------------------------
@@ -85,7 +85,7 @@ def report
 
   def record(result)
     super
-    io.puts "%s#%s = %.2f s = %s" % [result.class,
+    io.puts "%s#%s = %.2f s = %s" % [result.klass,
                                      result.name,
                                      result.time,
                                      result.result_code]
diff --git a/src/testup/gems/minitest-5.15.0.gem b/src/testup/gems/minitest-5.15.0.gem
new file mode 100644
index 0000000..bb3c247
Binary files /dev/null and b/src/testup/gems/minitest-5.15.0.gem differ
diff --git a/src/testup/gems/minitest-5.4.3.gem b/src/testup/gems/minitest-5.4.3.gem
deleted file mode 100644
index 3614461..0000000
Binary files a/src/testup/gems/minitest-5.4.3.gem and /dev/null differ
diff --git a/src/testup/reporter.rb b/src/testup/reporter.rb
index f99001d..98d18ec 100644
--- a/src/testup/reporter.rb
+++ b/src/testup/reporter.rb
@@ -1,6 +1,6 @@
 #-------------------------------------------------------------------------------
 #
-# Copyright 2013-2018 Trimble Inc.
+# Copyright 2013-2024 Trimble Inc.
 # License: The MIT License (MIT)
 #
 #-------------------------------------------------------------------------------
@@ -58,7 +58,7 @@ def record(result)
 
   def process_results(result)
     {
-      test_case_name: result.class.name,
+      test_case_name: result.klass,
       test_name:      result.name,
       run_time:       result.time,
       skipped:        result.skipped?,