1 files changed, 133 insertions, 6 deletions
diff --git a/spec/ruby/core/string/capitalize_spec.rb b/spec/ruby/core/string/capitalize_spec.rb
index e279f7d061..10f9ab00a1 100644
--- a/spec/ruby/core/string/capitalize_spec.rb
+++ b/spec/ruby/core/string/capitalize_spec.rb
@@ -26,8 +26,65 @@ describe "String#capitalize" do
   end
 
   ruby_version_is '2.4' do
-    it "works for all of Unicode" do
-      "äöü".capitalize.should == "Äöü"
+    describe "full Unicode case mapping" do
+      it "works for all of Unicode with no option" do
+        "äöÜ".capitalize.should == "Äöü"
+      end
+
+      it "only capitalizes the first resulting character when upcasing a character produces a multi-character sequence" do
+        "ß".capitalize.should == "Ss"
+      end
+
+      it "updates string metadata" do
+        capitalized = "ßeT".capitalize
+
+        capitalized.should == "Sset"
+        capitalized.size.should == 4
+        capitalized.bytesize.should == 4
+        capitalized.ascii_only?.should be_true
+      end
+    end
+
+    describe "ASCII-only case mapping" do
+      it "does not capitalize non-ASCII characters" do
+        "ßet".capitalize(:ascii).should == "ßet"
+      end
+    end
+
+    describe "full Unicode case mapping adapted for Turkic languages" do
+      it "capitalizes ASCII characters according to Turkic semantics" do
+        "iSa".capitalize(:turkic).should == "İsa"
+      end
+
+      it "allows Lithuanian as an extra option" do
+        "iSa".capitalize(:turkic, :lithuanian).should == "İsa"
+      end
+
+      it "does not allow any other additional option" do
+        lambda { "iSa".capitalize(:turkic, :ascii) }.should raise_error(ArgumentError)
+      end
+    end
+
+    describe "full Unicode case mapping adapted for Lithuanian" do
+      it "currently works the same as full Unicode case mapping" do
+        "iß".capitalize(:lithuanian).should == "Iß"
+      end
+
+      it "allows Turkic as an extra option (and applies Turkic semantics)" do
+        "iß".capitalize(:lithuanian, :turkic).should == "İß"
+      end
+
+      it "does not allow any other additional option" do
+        lambda { "iß".capitalize(:lithuanian, :ascii) }.should raise_error(ArgumentError)
+      end
+    end
+
+    it "does not allow the :fold option for upcasing" do
+      lambda { "abc".capitalize(:fold) }.should raise_error(ArgumentError)
+    end
+
+    it "does not allow invalid options" do
+      lambda { "abc".capitalize(:invalid_option) }.should raise_error(ArgumentError)
     end
   end
 
@@ -45,10 +102,80 @@ describe "String#capitalize!" do
   end
 
   ruby_version_is '2.4' do
-    it "capitalizes self in place for all of Unicode" do
-      a = "äöü"
-      a.capitalize!.should equal(a)
-      a.should == "Äöü"
+    describe "full Unicode case mapping" do
+      it "modifies self in place for all of Unicode with no option" do
+        a = "äöÜ"
+        a.capitalize!
+        a.should == "Äöü"
+      end
+
+      it "only capitalizes the first resulting character when upcasing a character produces a multi-character sequence" do
+        a = "ß"
+        a.capitalize!
+        a.should == "Ss"
+      end
+
+      it "updates string metadata" do
+        capitalized = "ßeT"
+        capitalized.capitalize!
+
+        capitalized.should == "Sset"
+        capitalized.size.should == 4
+        capitalized.bytesize.should == 4
+        capitalized.ascii_only?.should be_true
+      end
+    end
+
+    describe "modifies self in place for ASCII-only case mapping" do
+      it "does not capitalize non-ASCII characters" do
+        a = "ßet"
+        a.capitalize!(:ascii)
+        a.should == "ßet"
+      end
+    end
+
+    describe "modifies self in place for full Unicode case mapping adapted for Turkic languages" do
+      it "capitalizes ASCII characters according to Turkic semantics" do
+        a = "iSa"
+        a.capitalize!(:turkic)
+        a.should == "İsa"
+      end
+
+      it "allows Lithuanian as an extra option" do
+        a = "iSa"
+        a.capitalize!(:turkic, :lithuanian)
+        a.should == "İsa"
+      end
+
+      it "does not allow any other additional option" do
+        lambda { a = "iSa"; a.capitalize!(:turkic, :ascii) }.should raise_error(ArgumentError)
+      end
+    end
+
+    describe "modifies self in place for full Unicode case mapping adapted for Lithuanian" do
+      it "currently works the same as full Unicode case mapping" do
+        a = "iß"
+        a.capitalize!(:lithuanian)
+        a.should == "Iß"
+      end
+
+      it "allows Turkic as an extra option (and applies Turkic semantics)" do
+        a = "iß"
+        a.capitalize!(:lithuanian, :turkic)
+        a.should == "İß"
+      end
+
+      it "does not allow any other additional option" do
+        lambda { a = "iß"; a.capitalize!(:lithuanian, :ascii) }.should raise_error(ArgumentError)
+      end
+    end
+
+    it "does not allow the :fold option for upcasing" do
+      lambda { a = "abc"; a.capitalize!(:fold) }.should raise_error(ArgumentError)
+    end
+
+    it "does not allow invalid options" do
+      lambda { a = "abc"; a.capitalize!(:invalid_option) }.should raise_error(ArgumentError)
     end
   end