diff --git a/README.md b/README.md
index 63fc9c9..770f7b8 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ The package can be installed by adding `phone_verification` to your list of depe
 def deps do
   [
     {:jason, "~> 1.1"}, # or any other JSON library
-    {:phone_verification, "~> 0.1.0"}
+    {:phone_verification, "~> 0.3.0"}
   ]
 end
 ```
@@ -24,7 +24,8 @@ config :phone_verification,
 
 config :phone_verification, PhoneVerification.Provider.Authy,
   json_codec: Jason,
-  api_key: System.get_env("AUTHY_API_KEY")
+  api_key: System.get_env("AUTHY_API_KEY"),
+  mocks: %{}
 ```
 
 ## Usage
diff --git a/config/config.exs b/config/config.exs
index 0b6e45d..857cb18 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -8,4 +8,6 @@ config :phone_verification,
 
 config :phone_verification, PhoneVerification.Provider.Authy,
   # json_codec: Jason,
-  api_key: System.get_env("AUTHY_API_KEY")
+  api_key: System.get_env("AUTHY_API_KEY"),
+  # example: %{ "+380001234567" => "0000", "+380001234568" => "1234" }
+  mocks: %{}
diff --git a/lib/phone_verification.ex b/lib/phone_verification.ex
index f0cf6ec..fab0dc0 100644
--- a/lib/phone_verification.ex
+++ b/lib/phone_verification.ex
@@ -7,6 +7,20 @@ defmodule PhoneVerification do
     Application.get_env(:phone_verification, key)
   end
 
+  @spec start(%{
+          required(:phone_number) => PhoneVerification.PhoneNumber.t(),
+          required(:via) => :sms | :call,
+          optional(:locale) => String.t(),
+          optional(:code_length) => non_neg_integer(),
+          optional(:custom_code) => PhoneVerification.verification_code()
+        }) ::
+          {:ok,
+           %{
+             message: String.t(),
+             carrier: String.t(),
+             seconds_to_expire: non_neg_integer()
+           }}
+          | {:error, %{message: String.t(), code: non_neg_integer()}}
   def start(params) do
     config(:default)
     |> Enum.into(%{})
@@ -14,6 +28,10 @@ defmodule PhoneVerification do
     |> config(:provider).start()
   end
 
+  @spec check(%{
+          required(:phone_number) => PhoneVerification.PhoneNumber.t(),
+          required(:verification_code) => PhoneVerification.verification_code()
+        }) :: {:ok, %{message: String.t()}} | {:error, %{message: String.t(), code: String.t()}}
   def check(params) do
     config(:provider).check(params)
   end
diff --git a/lib/phone_verification/provider/authy.ex b/lib/phone_verification/provider/authy.ex
index d433bb9..9368092 100644
--- a/lib/phone_verification/provider/authy.ex
+++ b/lib/phone_verification/provider/authy.ex
@@ -2,17 +2,33 @@ defmodule PhoneVerification.Provider.Authy do
   @behaviour PhoneVerification.Provider
 
   @base_url "https://api.authy.com/protected/json/phones/verification/"
+  # actually, it can be infinity, but we have to return a number
+  @expiration_time_for_mock_phone_number_security_code 600
 
+  @mock_carrier "life:) - Astelit"
   @supported_keys [:phone_number, :country_code, :via, :locale, :code_length, :custom_code]
   @impl true
-  def start(params) do
-    request(:post, "start", transform_params(params, @supported_keys))
+  def start(%{phone_number: phone_number} = params) do
+    if mock_number?(phone_number) do
+      {:ok,
+       %{
+         seconds_to_expire: @expiration_time_for_mock_phone_number_security_code,
+         message: "Requested verification using mock: #{phone_number}.",
+         carrier: @mock_carrier
+       }}
+    else
+      request(:post, "start", transform_params(params, @supported_keys))
+    end
   end
 
   @supported_keys [:phone_number, :country_code, :verification_code]
   @impl true
-  def check(params) do
-    request(:get, "check", transform_params(params, @supported_keys))
+  def check(%{phone_number: phone_number} = params) do
+    if mock_number?(phone_number) do
+      check_mock_number(params)
+    else
+      request(:get, "check", transform_params(params, @supported_keys))
+    end
   end
 
   defp request(method, action, params) do
@@ -77,4 +93,16 @@ defmodule PhoneVerification.Provider.Authy do
     |> PhoneVerification.config()
     |> Keyword.fetch!(key)
   end
+
+  defp mock_number?(phone_number) do
+    !is_nil(config(:mocks)[to_string(phone_number)])
+  end
+
+  defp check_mock_number(%{phone_number: phone_number, verification_code: code}) do
+    if config(:mocks)[to_string(phone_number)] == code do
+      {:ok, %{message: "Verification code is correct."}}
+    else
+      {:error, %{message: "Verification code is incorrect", code: 60_022}}
+    end
+  end
 end
diff --git a/mix.exs b/mix.exs
index 9bb1ef7..7f17743 100644
--- a/mix.exs
+++ b/mix.exs
@@ -4,7 +4,7 @@ defmodule PhoneVerification.MixProject do
   def project do
     [
       app: :phone_verification,
-      version: "0.2.0",
+      version: "0.3.0",
       elixir: "~> 1.3",
       start_permanent: Mix.env() == :prod,
       description: description(),