Fix tests on older Rubies

Endless/beginless ranges are not valid syntax pre 2.6

Author: tomdalling

.rspec

@@ -2,5 +2,5 @@
 --format documentation
 --color
 <% if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.7') %>
-  --exclude-pattern spec/pattern_matching_spec.rb
+  --exclude-pattern spec/pattern_matching_spec.rb,spec/range_of_endless_spec.rb
 <% end %>

spec/pattern_matching_spec.rb

@@ -1,3 +1,4 @@
+# Only works in Ruby 2.7+
 RSpec.describe ValueSemantics, 'pattern matching integration' do
   shared_examples 'pattern matching' do
     it 'deconstructs to a hash' do

spec/range_of_endless_spec.rb

@@ -0,0 +1,12 @@
+# Only works in Ruby 2.6+
+RSpec.describe ValueSemantics::RangeOf do
+  subject { described_class.new(Integer) }
+
+  it 'matches beginless ranges' do
+    is_expected.to be === (1..)
+  end
+
+  it 'matches endless ranges' do
+    is_expected.to be === (..10)
+  end
+end

spec/range_of_spec.rb

@@ -5,14 +5,6 @@
     is_expected.to be === (1..10)
   end
 
-  it 'matches beginless ranges' do
-    is_expected.to be === (1..)
-  end
-
-  it 'matches endless ranges' do
-    is_expected.to be === (..10)
-  end
-
   it 'does not match ranges whose `begin` does not match the subvalidator' do
     expect(subject === (1.0..10)).to be(false)
   end