diff --git a/lib/imbecile/code_point_range.rb b/lib/imbecile/code_point_range.rb
index 513a6d0..b1d9a96 100644
--- a/lib/imbecile/code_point_range.rb
+++ b/lib/imbecile/code_point_range.rb
@@ -50,6 +50,8 @@ module Imbecile
           if code_point_range.first > (last_cp + 1)
             new_ranges << CodePointRange.new(last_cp + 1, code_point_range.first - 1)
             last_cp = code_point_range.last
+          else
+            last_cp = [last_cp, code_point_range.last].max
           end
         end
         if last_cp < MAX_CODE_POINT
diff --git a/spec/imbecile/code_point_range_spec.rb b/spec/imbecile/code_point_range_spec.rb
new file mode 100644
index 0000000..e62edad
--- /dev/null
+++ b/spec/imbecile/code_point_range_spec.rb
@@ -0,0 +1,87 @@
+module Imbecile
+  describe CodePointRange do
+
+    describe "#<=>" do
+      it "sorts ranges" do
+        arr = [
+          CodePointRange.new(100,102),
+          CodePointRange.new(65, 68),
+          CodePointRange.new(65, 65),
+          CodePointRange.new(100, 100),
+          CodePointRange.new(68, 70),
+        ]
+        arr.sort!
+        expect(arr[0]).to eq CodePointRange.new(65, 65)
+        expect(arr[1]).to eq CodePointRange.new(65, 68)
+        expect(arr[2]).to eq CodePointRange.new(68, 70)
+        expect(arr[3]).to eq CodePointRange.new(100, 100)
+        expect(arr[4]).to eq CodePointRange.new(100, 102)
+      end
+    end
+
+    describe "#include?" do
+      it "returns whether the code point is included in the range" do
+        expect(CodePointRange.new(100).include?(100)).to be_truthy
+        expect(CodePointRange.new(100, 100).include?(99)).to be_falsey
+        expect(CodePointRange.new(100, 100).include?(101)).to be_falsey
+        expect(CodePointRange.new(100, 120).include?(99)).to be_falsey
+        expect(CodePointRange.new(100, 120).include?(100)).to be_truthy
+        expect(CodePointRange.new(100, 120).include?(110)).to be_truthy
+        expect(CodePointRange.new(100, 120).include?(120)).to be_truthy
+        expect(CodePointRange.new(100, 120).include?(121)).to be_falsey
+      end
+
+      it "returns whether the range is included in the range" do
+        expect(CodePointRange.new(100).include?(CodePointRange.new(100))).to be_truthy
+        expect(CodePointRange.new(100, 100).include?(CodePointRange.new(99))).to be_falsey
+        expect(CodePointRange.new(100, 100).include?(CodePointRange.new(99, 100))).to be_falsey
+        expect(CodePointRange.new(100, 120).include?(CodePointRange.new(90, 110))).to be_falsey
+        expect(CodePointRange.new(100, 120).include?(CodePointRange.new(110, 130))).to be_falsey
+        expect(CodePointRange.new(100, 120).include?(CodePointRange.new(100, 120))).to be_truthy
+        expect(CodePointRange.new(100, 120).include?(CodePointRange.new(100, 110))).to be_truthy
+        expect(CodePointRange.new(100, 120).include?(CodePointRange.new(110, 120))).to be_truthy
+        expect(CodePointRange.new(100, 120).include?(CodePointRange.new(102, 118))).to be_truthy
+      end
+    end
+
+    describe ".invert_ranges" do
+      it "inverts ranges" do
+        expect(CodePointRange.invert_ranges(
+          [CodePointRange.new(60, 90),
+           CodePointRange.new(80, 85),
+           CodePointRange.new(80, 100),
+           CodePointRange.new(101),
+           CodePointRange.new(200, 300)])).to eq [
+             CodePointRange.new(0, 59),
+             CodePointRange.new(102, 199),
+             CodePointRange.new(301, 0xFFFFFFFF)]
+        expect(CodePointRange.invert_ranges(
+          [CodePointRange.new(0, 500),
+           CodePointRange.new(7000, 0xFFFFFFFF)])).to eq [
+             CodePointRange.new(501, 6999)]
+      end
+    end
+
+    describe ".first_subrange" do
+      it "returns the first subrange to split" do
+        expect(CodePointRange.first_subrange(
+          [CodePointRange.new(65, 90),
+           CodePointRange.new(66, 66),
+           CodePointRange.new(80, 90)])).to eq CodePointRange.new(65)
+        expect(CodePointRange.first_subrange(
+          [CodePointRange.new(65, 90)])).to eq CodePointRange.new(65, 90)
+        expect(CodePointRange.first_subrange(
+          [CodePointRange.new(65, 90),
+           CodePointRange.new(80, 90)])).to eq CodePointRange.new(65, 79)
+        expect(CodePointRange.first_subrange(
+          [CodePointRange.new(65, 90),
+           CodePointRange.new(65, 100),
+           CodePointRange.new(65, 95)])).to eq CodePointRange.new(65, 90)
+        expect(CodePointRange.first_subrange(
+          [CodePointRange.new(100, 120),
+           CodePointRange.new(70, 90)])).to eq CodePointRange.new(70, 90)
+      end
+    end
+
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index f772d77..98461d1 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -5,9 +5,6 @@ RSpec.configure do |config|
   # Enable flags like --only-failures and --next-failure
   config.example_status_persistence_file_path = ".rspec_status"
 
-  # Disable RSpec exposing methods globally on `Module` and `main`
-  config.disable_monkey_patching!
-
   config.expect_with :rspec do |c|
     c.syntax = :expect
   end