diff --git a/lib/bytes.rb b/lib/bytes.rb
index 2386cb1..44d8980 100644
--- a/lib/bytes.rb
+++ b/lib/bytes.rb
@@ -14,6 +14,7 @@ def bytes_to_str(data)
   data.unpack('H*').join
 end
 
+# TODO: remove?
 def get_byte(data, start = 0, num = 1)
   data[start...(start + num)].unpack('H*').join.upcase
 end
diff --git a/spec/07_bytes_spec.rb b/spec/07_bytes_spec.rb
new file mode 100644
index 0000000..be3e521
--- /dev/null
+++ b/spec/07_bytes_spec.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require_relative '../lib/bytes'
+
+describe 'Bytes', :bytes do
+  context '#str_hex' do
+    it 'Should format "\xFF" to "FF"' do
+      expect(str_hex("\xFF")).to eq('FF')
+    end
+    it 'Should format "\x01" to "01"' do
+      expect(str_hex("\x01")).to eq('01')
+    end
+    it 'Should format "\x01\x02" to "01 02"' do
+      expect(str_hex("\x01\x02")).to eq('01 02')
+    end
+  end
+  context '#str_bytes' do
+    it 'Should format "ff" to [255]' do
+      expect(str_bytes('ff')).to eq([255])
+    end
+    it 'Should format "FF" to [255]' do
+      expect(str_bytes('FF')).to eq([255])
+    end
+    it 'Should format "01" to [1]' do
+      expect(str_bytes('01')).to eq([1])
+    end
+    it 'Should format "0101" to [1, 1]' do
+      expect(str_bytes('0101')).to eq([1, 1])
+    end
+  end
+  context '#bytes_to_str' do
+    it 'Should format "\xff" to "ff"' do
+      expect(bytes_to_str("\xff")).to eq('ff')
+    end
+    it 'Should format "\x01" to "01"' do
+      expect(bytes_to_str("\x01")).to eq('01')
+    end
+    it 'Should format "\x01\x01" to "0101"' do
+      expect(bytes_to_str("\x01\x01")).to eq('0101')
+    end
+  end
+end