diff --git a/spec/cbor_spec.cr b/spec/cbor_spec.cr
index 4d6dc79..ed1b0ac 100644
--- a/spec/cbor_spec.cr
+++ b/spec/cbor_spec.cr
@@ -1,5 +1,115 @@
 require "./spec_helper"
 
-describe CBOR do
-  # TODO: Write tests
+class Location
+  include CBOR::Serializable
+
+  @[CBOR::Field(key: "lat")]
+  property latitude : Float64
+
+  @[CBOR::Field(key: "lng")]
+  property longitude : Float64
+
+  def initialize(@latitude, @longitude)
+  end
 end
+
+class House
+  include CBOR::Serializable
+
+  property address   : String
+  property location  : Location?
+
+  def initialize(@address)
+  end
+end
+
+class Person
+  include CBOR::Serializable
+  include CBOR::Serializable::Unmapped
+
+  property name : String?
+  def initialize(@name = nil)
+  end
+end
+
+
+describe CBOR do
+  describe "basics: to_cbor" do
+    it "empty array" do
+      empty_array_cbor = [] of Nil
+      empty_array_cbor.to_cbor.hexstring.should eq "80"
+    end
+
+    it "array - strings" do
+      ["a", "b", "c"].to_cbor.hexstring.should eq "83616161626163"
+    end
+
+    it "empty hash" do
+      empty = {} of Nil => Nil
+      cbor_stuff = empty.to_cbor
+      cbor_stuff.hexstring.should eq "a0"
+    end
+
+    it "hash" do
+      {"a" => 10, "b" => true, "c" => nil}.to_cbor.hexstring.should eq "a361610a6162f56163f6"
+    end
+
+    it "union String | Int32" do
+      value = (String | Int32).from_cbor(30.to_cbor).to_cbor
+      value.hexstring.should eq "181e"
+    end
+    it "union (String | Int32)" do
+      value = (String | Int32).from_cbor("blah".to_cbor).to_cbor
+      value.hexstring.should eq "64626c6168"
+    end
+    it "union (Bool | Int32)" do
+      value = (Bool | Int32).from_cbor(30.to_cbor).to_cbor
+      value.hexstring.should eq "181e"
+    end
+    it "union (Bool | Int32)" do
+      value = (Bool | Int32).from_cbor(false.to_cbor).to_cbor
+      value.hexstring.should eq "f4"
+    end
+    it "union (String | Bool | Int32)" do
+      value = (String | Bool | Int32).from_cbor("hello".to_cbor).to_cbor
+      value.hexstring.should eq "6568656c6c6f"
+    end
+    it "union (String | Nil | Int32)" do
+      value = (String | Nil | Int32).from_cbor(nil.to_cbor).to_cbor
+      value.hexstring.should eq "f6"
+    end
+  end
+
+  describe "CBOR library annotations and features" do
+    it "House#to_cbor with CBOR::Field annotations" do
+      house = House.new "my address"
+      house.location = Location.new 1.1, 1.2
+      house.to_cbor.hexstring.should eq "a267616464726573736a6d792061646472657373686c6f636174696f6ea2636c6174fb3ff199999999999a636c6e67fb3ff3333333333333"
+    end
+
+    it "House#from_cbor with CBOR::Field annotations" do
+      other_house = House.new "my address"
+      other_house.location = Location.new 1.1, 1.2
+
+      house = House.from_cbor other_house.to_cbor
+      house.to_cbor.hexstring.should eq "a267616464726573736a6d792061646472657373686c6f636174696f6ea2636c6174fb3ff199999999999a636c6e67fb3ff3333333333333"
+    end
+
+    it "Person#from_cbor with unmapped values" do
+      h = Hash(String | Int32, String | Int32).new
+      h["name"] = "Alice"
+      h["age"]  = 30
+      h["size"] = 160
+      alice = Person.from_cbor h.to_cbor
+      alice.to_cbor.hexstring.should eq "a3646e616d6565416c69636563616765181e6473697a6518a0"
+    end
+
+    it "Person#to_cbor with unmapped values" do
+      alice = Person.new "Alice"
+      alice.cbor_unmapped["age"] = 30
+      alice.cbor_unmapped["size"] = 160
+      alice.to_cbor.hexstring.should eq "a3646e616d6565416c69636563616765181e6473697a6518a0"
+    end
+  end
+end
+