Update the :ruby25 job

Author: chrisseaton

ci.jsonnet

@@ -386,8 +386,8 @@ local part_definitions = {
       run+: [
         ["mx", "unittest", "org.truffleruby"],
         ["mx", "tck"],
-      ] + jt(["test", "specs"] + self["$.run.specs"].test_spec_options) +
-          jt(["test", "specs", ":ruby25"]),
+      ] + jt(["test", "specs"] + self["$.run.specs"].test_spec_options),
+              # + jt(["test", "specs", ":next"]) disabled as it's currently empty and MSpec doesn't support empty sets of files
     },
 
     test_fast: {

doc/contributor/workflow.md

@@ -191,8 +191,9 @@ $ PRETEND_RUBY_VERSION=2.5.0 jt test spec/ruby/core/integer/digits_spec.rb
 
 This also works for `jt tag`/`jt untag`.
 
-When working on a 2.4/2.5 feature, add the spec file in the corresponding file
-list (`:ruby25`) in `spec/truffle.mspec` so that the specs are run in CI too.
+When working on a feature from the next version of Ruby, add the spec file in
+the corresponding file list (`:next`) in `spec/truffle.mspec` so that the
+specs are run in CI too.
 
 ## How to fix a failing MRI test
 

spec/truffle.mspec

@@ -93,16 +93,7 @@ class MSpecScript
     "spec/truffle/capi"
   ]
 
-  set :ruby25, [
-    "spec/ruby/core/kernel/yield_self_spec.rb",
-    "spec/ruby/core/method/case_compare_spec.rb",
-    "spec/ruby/core/enumerable/all_spec.rb",
-    "spec/ruby/core/enumerable/any_spec.rb",
-    "spec/ruby/core/enumerable/none_spec.rb",
-    "spec/ruby/core/enumerable/one_spec.rb",
-    "spec/ruby/core/exception/full_message_spec.rb",
-    "spec/ruby/core/hash/transform_keys_spec.rb",
-    "spec/ruby/library/mathn/mathn_spec.rb",
+  set :next, [
   ]
 
   set :backtrace_filter, /mspec\//
@@ -147,15 +138,15 @@ class MSpecScript
   set :files, get(:command_line) + get(:language) + get(:core) + get(:library) + get(:truffle) + get(:security)
 
   # All specs, including specs needing C-extensions support.
-  # 2.4/2.5 specs are not included as they need to run in a separate process.
+  # Next version specs are not included as they need to run in a separate process.
   set :all, get(:files) + get(:capi) + get(:truffle_capi) + get(:library_cext)
 end
 
 if MSpecScript.child_process?
   if version = ENV["PRETEND_RUBY_VERSION"]
     ::VersionGuard::FULL_RUBY_VERSION = SpecVersion.new(version)
-  elsif ARGV.include? ":ruby25"
-    ::VersionGuard::FULL_RUBY_VERSION = SpecVersion.new("2.5.3")
+  elsif ARGV.include? ":next"
+    ::VersionGuard::FULL_RUBY_VERSION = SpecVersion.new("2.7.0")
   end
 
   # We do not use Ruby 2.5's FrozenError yet