1 files changed, 20 insertions, 0 deletions
diff --git a/spec/ruby/core/string/casecmp_spec.rb b/spec/ruby/core/string/casecmp_spec.rb
index 9e89e1314d..87be999964 100644
--- a/spec/ruby/core/string/casecmp_spec.rb
+++ b/spec/ruby/core/string/casecmp_spec.rb
@@ -37,6 +37,10 @@ describe "String#casecmp independent of case" do
     end
   end
 
+  it "returns nil if incompatible encodings" do
+    "あれ".casecmp("れ".encode(Encoding::EUC_JP)).should be_nil
+  end
+
   describe "in UTF-8 mode" do
     describe "for non-ASCII characters" do
       before :each do
@@ -96,6 +100,12 @@ describe "String#casecmp independent of case" do
     it "returns 1 when numerically greater than other" do
       @lower_a_tilde.casecmp(@upper_a_tilde).should == 1
     end
+
+    ruby_version_is "2.4" do
+      it "does not case fold" do
+        "ß".casecmp("ss").should == 1
+      end
+    end
   end
 
   describe "when comparing a subclass instance" do
@@ -138,6 +148,10 @@ ruby_version_is "2.4" do
       "abc".casecmp?(other).should == true
     end
 
+    it "returns nil if incompatible encodings" do
+      "あれ".casecmp?("れ".encode(Encoding::EUC_JP)).should be_nil
+    end
+
     describe 'for UNICODE characters' do
       it 'returns true when downcase(:fold) on unicode' do
         'äöü'.casecmp?('ÄÖÜ').should == true
@@ -181,6 +195,12 @@ ruby_version_is "2.4" do
       end
     end
 
+    ruby_version_is "2.4" do
+      it "case folds" do
+        "ß".casecmp?("ss").should be_true
+      end
+    end
+
     ruby_version_is "2.4" ... "2.5" do
       it "raises a TypeError if other can't be converted to a string" do
         lambda { "abc".casecmp?(mock('abc')) }.should raise_error(TypeError)