Disallow downgrades to too old versions

Consider the version original included with each ruby as the minimum
supported version.

1 files changed, 20 insertions, 0 deletions

diff --git a/test/rubygems/test_gem_commands_update_command.rb b/test/rubygems/test_gem_commands_update_command.rb
index 65a70b2b74..eed799c5aa 100644
--- a/test/rubygems/test_gem_commands_update_command.rb
+++ b/test/rubygems/test_gem_commands_update_command.rb
@@ -158,6 +158,26 @@ class TestGemCommandsUpdateCommand < Gem::TestCase
     assert_empty out
   end
 
+  def test_execute_system_specific_older_than_minimum_supported_rubygems
+    spec_fetcher do |fetcher|
+      fetcher.download 'rubygems-update', "2.5.1" do |s|
+        s.files = %w[setup.rb]
+      end
+    end
+
+    @cmd.options[:args]          = []
+    @cmd.options[:system]        = "2.5.1"
+
+    assert_raises Gem::MockGemUi::TermError do
+      use_ui @ui do
+        @cmd.execute
+      end
+    end
+
+    assert_empty @ui.output
+    assert_equal "ERROR:  rubygems 2.5.1 is not supported. The oldest supported version is 2.5.2\n", @ui.error
+  end
+
   def test_execute_system_specific_older_than_3_2_removes_plugins_dir
     spec_fetcher do |fetcher|
       fetcher.download 'rubygems-update', 3.1 do |s|