diff --git a/lib/packer.rb b/lib/packer.rb
index 47e05f2..a17b9fb 100644
--- a/lib/packer.rb
+++ b/lib/packer.rb
@@ -46,6 +46,7 @@ class Packer
   end
 
   def self.pack_big_int(sign, num)
+    num += 1 if sign == '1'
     num_bits = num.to_s(2)
     first = "1#{sign}#{num_bits[-6..]}"
 
@@ -129,32 +130,3 @@ class Unpacker
     bits.join.to_i(2) * sign
   end
 end
-
-def todo_make_this_rspec_test
-  # # single byte int
-  # p Packer.pack_int(1) == [1]
-  # p Packer.pack_int(3) == [3]
-  # p Packer.pack_int(16) == [16]
-  # p Packer.pack_int(63) == [63]
-
-  # # negative single byte
-  # p Packer.pack_int(-1) == [64]
-  # p Packer.pack_int(-2) == [65]
-
-  # p Packer.pack_int(-1).first.to_s(2) == '1000000'
-  # p Packer.pack_int(-2).first.to_s(2) == '1000001'
-  # p Packer.pack_int(-3).first.to_s(2) == '1000010'
-  # p Packer.pack_int(-4).first.to_s(2) == '1000011'
-
-  p Packer.pack_int(64).map { |e| e.to_s(2).rjust(8, '0') } == %w[10000000 00000001]
-  p Packer.pack_int(-64).map { |e| e.to_s(2).rjust(8, '0') } == %w[11000000 00000000]
-
-  # # multi byte int
-  # p Packer.pack_int(64) == [128, 1]
-  # p Packer.pack_int(99999999999999999) == [191, 131, 255, 147, 246, 194, 215, 232, 88]
-
-  # # string
-  # p Packer.pack_str("A") == [65, 0]
-end
-
-# todo_make_this_rspec_test
diff --git a/spec/04_packer_spec.rb b/spec/04_packer_spec.rb
new file mode 100644
index 0000000..21fb465
--- /dev/null
+++ b/spec/04_packer_spec.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require_relative '../lib/packer'
+
+describe 'Packer', :packer do
+  context 'Pack strings' do
+    it 'Should pack a single string' do
+      expect(Packer.pack_str('A')).to eq([65, 0])
+    end
+  end
+
+  context 'Pack single byte integers' do
+    it 'Should pack positive' do
+      expect(Packer.pack_int(1)).to eq([1])
+      expect(Packer.pack_int(3)).to eq([3])
+      expect(Packer.pack_int(16)).to eq([16])
+      expect(Packer.pack_int(63)).to eq([63])
+    end
+
+    it 'Should pack negative' do
+      expect(Packer.pack_int(-1)).to eq([64])
+      expect(Packer.pack_int(-2)).to eq([65])
+    end
+
+    it 'Should pack negative match binary' do
+      expect(Packer.pack_int(-1).first.to_s(2)).to eq('1000000')
+      expect(Packer.pack_int(-2).first.to_s(2)).to eq('1000001')
+      expect(Packer.pack_int(-3).first.to_s(2)).to eq('1000010')
+      expect(Packer.pack_int(-4).first.to_s(2)).to eq('1000011')
+    end
+  end
+
+  context 'Pack multi byte integers' do
+    it 'Should pack positive' do
+      expect(Packer.pack_int(64).map { |e| e.to_s(2).rjust(8, '0') }).to eq(%w[10000000 00000001])
+      expect(Packer.pack_int(64)).to eq([128, 1])
+    end
+
+    it 'Should pack negative' do
+      expect(Packer.pack_int(-65).map { |e| e.to_s(2).rjust(8, '0') }).to eq(%w[11000001 00000001])
+    end
+
+    it 'Should pack large numbers' do
+      expect(Packer.pack_int(99_999_999_999_999_999)).to eq([191, 131, 255, 147, 246, 194, 215, 232, 88])
+    end
+  end
+end
diff --git a/spec/04_unpacker_spec.rb b/spec/05_unpacker_spec.rb
similarity index 100%
rename from spec/04_unpacker_spec.rb
rename to spec/05_unpacker_spec.rb