2 files changed, 17 insertions, 1 deletions
diff --git a/spec/ruby/library/erb/new_spec.rb b/spec/ruby/library/erb/new_spec.rb
index f18e25939e..a5aeeaeed1 100644
--- a/spec/ruby/library/erb/new_spec.rb
+++ b/spec/ruby/library/erb/new_spec.rb
@@ -138,4 +138,20 @@ END
     ERB.new(@eruby_str).result
     ->{ ERB.new("<%= list %>").result }.should raise_error(NameError)
   end
+
+  describe "warning about arguments" do
+    version_is ERB.version, "2.2.1" do #ruby_version_is "3.1" do
+      it "warns when passed safe_level and later arguments" do
+        -> {
+          ERB.new(@eruby_str, nil, '%')
+        }.should complain(/warning: Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments./)
+      end
+
+      it "does not warn when passed arguments as keyword argument" do
+        -> {
+          ERB.new(@eruby_str, trim_mode: '%')
+        }.should_not complain(/warning: Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments./)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/erb/run_spec.rb b/spec/ruby/library/erb/run_spec.rb
index 8c07442d8f..602e53ab38 100644
--- a/spec/ruby/library/erb/run_spec.rb
+++ b/spec/ruby/library/erb/run_spec.rb
@@ -6,7 +6,7 @@ describe "ERB#run" do
   # lambda { ... }.should output
   def _steal_stdout
     orig = $stdout
-    s = ''
+    s = +''
     def s.write(arg); self << arg.to_s; end
     $stdout = s
     begin