1 files changed, 14 insertions, 15 deletions
diff --git a/spec/ruby/core/string/rstrip_spec.rb b/spec/ruby/core/string/rstrip_spec.rb
index 4332b33b20..1638ea375d 100644
--- a/spec/ruby/core/string/rstrip_spec.rb
+++ b/spec/ruby/core/string/rstrip_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/strip'
@@ -29,7 +30,7 @@ end
 describe "String#rstrip!" do
   it "modifies self in place and returns self" do
     a = "  hello  "
-    a.rstrip!.should equal(a)
+    a.rstrip!.should.equal?(a)
     a.should == "  hello"
   end
 
@@ -51,31 +52,29 @@ describe "String#rstrip!" do
     "  ".rstrip.should == ""
   end
 
-  ruby_version_is '3.0' do
-    it "removes trailing NULL bytes and whitespace" do
-      a = "\000 goodbye \000"
-      a.rstrip!
-      a.should == "\000 goodbye"
-    end
+  it "removes trailing NULL bytes and whitespace" do
+    a = "\000 goodbye \000"
+    a.rstrip!
+    a.should == "\000 goodbye"
   end
 
   it "raises a FrozenError on a frozen instance that is modified" do
-    -> { "  hello  ".freeze.rstrip! }.should raise_error(FrozenError)
+    -> { "  hello  ".freeze.rstrip! }.should.raise(FrozenError)
   end
 
   # see [ruby-core:23666]
   it "raises a FrozenError on a frozen instance that would not be modified" do
-    -> { "hello".freeze.rstrip! }.should raise_error(FrozenError)
-    -> { "".freeze.rstrip!      }.should raise_error(FrozenError)
+    -> { "hello".freeze.rstrip! }.should.raise(FrozenError)
+    -> { "".freeze.rstrip!      }.should.raise(FrozenError)
   end
 
-  it "raises an ArgumentError if the last non-space codepoint is invalid" do
+  it "raises an Encoding::CompatibilityError if the last non-space codepoint is invalid" do
     s = "abc\xDF".force_encoding(Encoding::UTF_8)
-    s.valid_encoding?.should be_false
-    -> { s.rstrip! }.should raise_error(ArgumentError)
+    s.valid_encoding?.should == false
+    -> { s.rstrip! }.should.raise(Encoding::CompatibilityError)
 
     s = "abc\xDF   ".force_encoding(Encoding::UTF_8)
-    s.valid_encoding?.should be_false
-    -> { s.rstrip! }.should raise_error(ArgumentError)
+    s.valid_encoding?.should == false
+    -> { s.rstrip! }.should.raise(Encoding::CompatibilityError)
   end
 end