diff --git a/test/mri/tests/ruby/test_parse.rb b/test/mri/tests/ruby/test_parse.rb
index 6839581a0b71..7c0d5bfa6578 100644
--- a/test/mri/tests/ruby/test_parse.rb
+++ b/test/mri/tests/ruby/test_parse.rb
@@ -27,7 +27,7 @@ def test_else_without_rescue
   end
 
   def test_alias_backref
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /can't make alias|invalid argument being passed to `alias`/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /can't make alias/) do
       begin;
         alias $foo $1
       end;
@@ -85,7 +85,7 @@ class << o
     assert_equal([42, 42], [o.Foo, o.Bar])
     assert_equal([42, 42], [o::baz, o::qux])
 
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /Can't set variable|immutable variable as a write target/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /Can't set variable/) do
       begin;
         $1 ||= t.foo 42
       end;
@@ -193,13 +193,13 @@ def foo
   end
 
   def test_class_module
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /must be CONSTANT|expected a constant name/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /must be CONSTANT/) do
       begin;
         class foo; end
       end;
     end
 
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /in method body|unexpected class definition in a method definition/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /in method body/) do
       begin;
         def foo
           class Foo; end
@@ -295,7 +295,7 @@ def foo(@@foo); end
       end;
     end
 
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /cannot be an instance variable|expected a local variable name in the block parameters/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /cannot be an instance variable/) do
       begin;
         o.foo {|; @a| @a = 42 }
       end;
@@ -439,13 +439,13 @@ def test_duplicate_argument
       end;
     end
 
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /duplicated argument|repeated parameter name/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /duplicated argument/) do
       begin;
         1.times {|a, a|}
       end;
     end
 
-    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /duplicated argument|repeated parameter name/) do
+    assert_syntax_error("#{<<~"begin;"}\n#{<<~'end;'}", /duplicated argument/) do
       begin;
         def foo(a, a); end
       end;
@@ -652,12 +652,12 @@ def test_question
 
   def test_percent
     assert_equal(:foo, eval('%s(foo)'))
-    assert_syntax_error('%s', /unterminated quoted string|expected a closing delimiter for the dynamic symbol/)
-    assert_syntax_error('%ss', /unknown type|invalid `%` token/)
-    assert_syntax_error('%z()', /unknown type|invalid `%` token/)
-    assert_syntax_error("%\u3042", /unknown type|invalid `%` token/)
-    assert_syntax_error("%q\u3042", /unknown type|invalid `%` token/)
-    assert_syntax_error("%", /unterminated quoted string|invalid `%` token/)
+    assert_syntax_error('%s', /unterminated quoted string/)
+    assert_syntax_error('%ss', /unknown type/)
+    assert_syntax_error('%z()', /unknown type/)
+    assert_syntax_error("%\u3042", /unknown type/)
+    assert_syntax_error("%q\u3042", /unknown type/)
+    assert_syntax_error("%", /unterminated quoted string/)
   end
 
   def test_symbol
@@ -685,7 +685,7 @@ def test_symbol
   end
 
   def test_parse_string
-    assert_syntax_error("/\n", /unterminated|expected a closing delimiter for the regular expression/)
+    assert_syntax_error("/\n", /unterminated/)
   end
 
   def test_here_document
@@ -869,7 +869,7 @@ def test_block_dup
   end
 
   def test_set_backref
-    assert_syntax_error("$& = 1", /Can't set variable|immutable variable as a write target/)
+    assert_syntax_error("$& = 1", /Can't set variable/)
   end
 
   def test_arg_concat
@@ -1278,7 +1278,7 @@ def test_heredoc_unterminated_interpolation
   end
 
   def test_unexpected_token_error
-    assert_syntax_error('"x"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx', /unexpected|expected a newline or semicolon after the statement/)
+    assert_syntax_error('"x"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx', /unexpected/)
   end
 
   def test_unexpected_token_after_numeric
@@ -1298,7 +1298,7 @@ def test_truncated_source_line
   end
 
   def test_unterminated_regexp_error
-    e = assert_syntax_error("/x", /unterminated regexp meets end of file|expected a closing delimiter for the regular expression/)
+    e = assert_syntax_error("/x", /unterminated regexp meets end of file/)
     assert_not_match(/unexpected tSTRING_END/, e.message)
   end
 
@@ -1330,9 +1330,9 @@ def test_eof
   end
 
   def test_eof_in_def
-    assert_syntax_error("def m\n\0""end", /unexpected|cannot parse the expression/)
-    assert_syntax_error("def m\n\C-d""end", /unexpected|cannot parse the expression/)
-    assert_syntax_error("def m\n\C-z""end", /unexpected|cannot parse the expression/)
+    assert_syntax_error("def m\n\0""end", /unexpected/)
+    assert_syntax_error("def m\n\C-d""end", /unexpected/)
+    assert_syntax_error("def m\n\C-z""end", /unexpected/)
   end
 
   def test_unexpected_eof
diff --git a/test/mri/tests/ruby/test_pattern_matching.rb b/test/mri/tests/ruby/test_pattern_matching.rb
index 1641b631a5f0..74f039e7b96c 100644
--- a/test/mri/tests/ruby/test_pattern_matching.rb
+++ b/test/mri/tests/ruby/test_pattern_matching.rb
@@ -1161,8 +1161,7 @@ def test_hash_pattern
       end
     end
 
-    bug18890 = self.then do # TruffleRuby: keep the test but do not check the warning
-      # bug18890 = assert_warning(/(?:.*:[47]: warning: possibly useless use of a literal in void context\n){2}/) do
+    bug18890 = assert_warning(/(?:.*:[47]: warning: possibly useless use of a literal in void context\n){2}/) do
       eval("#{<<~';;;'}")
       proc do |i|
         case i
@@ -1248,13 +1247,13 @@ def test_hash_pattern
       case _
       in "#{a}": a
       end
-    }, /symbol literal with interpolation is not allowed|expected a label as the key in the hash pattern/)
+    }, /symbol literal with interpolation is not allowed/)
 
     assert_syntax_error(%q{
       case _
       in "#{a}":
       end
-    }, /symbol literal with interpolation is not allowed|expected a label as the key in the hash pattern/)
+    }, /symbol literal with interpolation is not allowed/)
   end
 
   def test_paren
diff --git a/test/mri/tests/ruby/test_refinement.rb b/test/mri/tests/ruby/test_refinement.rb
index 06ff9323402e..8771f8bc98e7 100644
--- a/test/mri/tests/ruby/test_refinement.rb
+++ b/test/mri/tests/ruby/test_refinement.rb
@@ -2572,15 +2572,11 @@ def test_refine_array_min_max
   class Bug17822
     module Ext
       refine(Bug17822) do
-        def foo
-          :refined
-        end
+        def foo = :refined
       end
     end
 
-    private def foo
-      :not_refined
-    end
+    private(def foo = :not_refined)
 
     module Client
       using Ext
diff --git a/test/mri/tests/ruby/test_require.rb b/test/mri/tests/ruby/test_require.rb
index 35274ccfc934..871912e4910b 100644
--- a/test/mri/tests/ruby/test_require.rb
+++ b/test/mri/tests/ruby/test_require.rb
@@ -221,7 +221,7 @@ def assert_syntax_error_backtrace
     Dir.mktmpdir do |tmp|
       req = File.join(tmp, "test.rb")
       File.write(req, ",\n")
-      e = assert_raise_with_message(SyntaxError, /unexpected|cannot parse the expression/) {
+      e = assert_raise_with_message(SyntaxError, /unexpected/) {
         yield req
       }
       assert_not_nil(bt = e.backtrace, "no backtrace")
@@ -237,7 +237,7 @@ def test_require_syntax_error
 
   def test_require_syntax_error_rescued
     assert_syntax_error_backtrace do |req|
-      assert_raise_with_message(SyntaxError, /unexpected|cannot parse the expression/) {require req}
+      assert_raise_with_message(SyntaxError, /unexpected/) {require req}
       require req
     end
   end
diff --git a/test/mri/tests/ruby/test_syntax.rb b/test/mri/tests/ruby/test_syntax.rb
index 04ab4eb70e11..cd84988efd34 100644
--- a/test/mri/tests/ruby/test_syntax.rb
+++ b/test/mri/tests/ruby/test_syntax.rb
@@ -600,28 +600,28 @@ def test_cmdarg_kwarg_lvar_clashing_method
   end
 
   def test_duplicated_arg
-    assert_syntax_error("def foo(a, a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a, a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_, _) end")
     (obj = Object.new).instance_eval("def foo(_, x, _) x end")
     assert_equal(2, obj.foo(1, 2, 3))
   end
 
   def test_duplicated_rest
-    assert_syntax_error("def foo(a, *a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a, *a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_, *_) end")
     (obj = Object.new).instance_eval("def foo(_, x, *_) x end")
     assert_equal(2, obj.foo(1, 2, 3))
   end
 
   def test_duplicated_opt
-    assert_syntax_error("def foo(a, a=1) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a, a=1) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_, _=1) end")
     (obj = Object.new).instance_eval("def foo(_, x, _=42) x end")
     assert_equal(2, obj.foo(1, 2))
   end
 
   def test_duplicated_opt_rest
-    assert_syntax_error("def foo(a=1, *a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a=1, *a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_=1, *_) end")
     (obj = Object.new).instance_eval("def foo(_, x=42, *_) x end")
     assert_equal(42, obj.foo(1))
@@ -633,7 +633,7 @@ def test_duplicated_rest_opt
   end
 
   def test_duplicated_rest_post
-    assert_syntax_error("def foo(*a, a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(*a, a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(*_, _) end")
     (obj = Object.new).instance_eval("def foo(*_, x, _) x end")
     assert_equal(2, obj.foo(1, 2, 3))
@@ -644,7 +644,7 @@ def test_duplicated_rest_post
   end
 
   def test_duplicated_opt_post
-    assert_syntax_error("def foo(a=1, a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a=1, a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_=1, _) end")
     (obj = Object.new).instance_eval("def foo(_=1, x, _) x end")
     assert_equal(2, obj.foo(1, 2, 3))
@@ -655,7 +655,7 @@ def test_duplicated_opt_post
   end
 
   def test_duplicated_kw
-    assert_syntax_error("def foo(a, a: 1) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a, a: 1) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_, _: 1) end")
     (obj = Object.new).instance_eval("def foo(_, x, _: 1) x end")
     assert_equal(3, obj.foo(2, 3))
@@ -666,7 +666,7 @@ def test_duplicated_kw
   end
 
   def test_duplicated_rest_kw
-    assert_syntax_error("def foo(*a, a: 1) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(*a, a: 1) end", /duplicated argument name/)
     assert_nothing_raised {def foo(*_, _: 1) end}
     (obj = Object.new).instance_eval("def foo(*_, x: 42, _: 1) x end")
     assert_equal(42, obj.foo(42))
@@ -677,7 +677,7 @@ def test_duplicated_rest_kw
   end
 
   def test_duplicated_opt_kw
-    assert_syntax_error("def foo(a=1, a: 1) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a=1, a: 1) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_=1, _: 1) end")
     (obj = Object.new).instance_eval("def foo(_=42, x, _: 1) x end")
     assert_equal(0, obj.foo(0))
@@ -685,7 +685,7 @@ def test_duplicated_opt_kw
   end
 
   def test_duplicated_kw_kwrest
-    assert_syntax_error("def foo(a: 1, **a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a: 1, **a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_: 1, **_) end")
     (obj = Object.new).instance_eval("def foo(_: 1, x: 42, **_) x end")
     assert_equal(42, obj.foo())
@@ -695,7 +695,7 @@ def test_duplicated_kw_kwrest
   end
 
   def test_duplicated_rest_kwrest
-    assert_syntax_error("def foo(*a, **a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(*a, **a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(*_, **_) end")
     (obj = Object.new).instance_eval("def foo(*_, x, **_) x end")
     assert_equal(1, obj.foo(1))
@@ -704,7 +704,7 @@ def test_duplicated_rest_kwrest
   end
 
   def test_duplicated_opt_kwrest
-    assert_syntax_error("def foo(a=1, **a) end", /duplicated argument name|repeated parameter name/)
+    assert_syntax_error("def foo(a=1, **a) end", /duplicated argument name/)
     assert_valid_syntax("def foo(_=1, **_) end")
     (obj = Object.new).instance_eval("def foo(_=42, x, **_) x end")
     assert_equal(1, obj.foo(1))
@@ -1792,7 +1792,7 @@ def test_numbered_parameter
     assert_syntax_error('-> {-> {_1}; _2}', /numbered parameter is already used/)
     assert_syntax_error('proc {_1; _1 = nil}', /Can't assign to numbered parameter _1/)
     assert_syntax_error('proc {_1 = nil}', /_1 is reserved for numbered parameter/)
-    # assert_syntax_error('_2=1', /_2 is reserved for numbered parameter/) # GR-30031
+    assert_syntax_error('_2=1', /_2 is reserved for numbered parameter/)
     assert_syntax_error('proc {|_3|}', /_3 is reserved for numbered parameter/)
     assert_syntax_error('def x(_4) end', /_4 is reserved for numbered parameter/)
     assert_syntax_error('def _5; end', /_5 is reserved for numbered parameter/)