diff --git a/config/config.exs b/config/config.exs
index 1b885c837..79abc90f4 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -31,7 +31,6 @@ config :livebook,
   learn_notebooks: [],
   plugs: [],
   shutdown_callback: nil,
-  storage: Livebook.Storage.Ets,
   update_instructions_url: nil,
   within_iframe: false,
   allowed_uri_schemes: []
diff --git a/lib/livebook/application.ex b/lib/livebook/application.ex
index a7e3d4b6c..fae7c36a6 100644
--- a/lib/livebook/application.ex
+++ b/lib/livebook/application.ex
@@ -19,7 +19,7 @@ defmodule Livebook.Application do
         # Start a supervisor for Livebook tasks
         {Task.Supervisor, name: Livebook.TaskSupervisor},
         # Start the storage module
-        Livebook.Storage.current(),
+        Livebook.Storage,
         # Start the periodic version check
         Livebook.UpdateCheck,
         # Periodic measurement of system resources
diff --git a/lib/livebook/settings.ex b/lib/livebook/settings.ex
index e375dc478..01b3b7d48 100644
--- a/lib/livebook/settings.ex
+++ b/lib/livebook/settings.ex
@@ -82,16 +82,12 @@ defmodule Livebook.Settings do
   @spec remove_file_system(file_system_id()) :: :ok
   def remove_file_system(file_system_id) do
     if default_file_system_id() == file_system_id do
-      storage().delete_key(:settings, "global", :default_file_system_id)
+      Livebook.Storage.delete_key(:settings, "global", :default_file_system_id)
     end
 
     Livebook.NotebookManager.remove_file_system(file_system_id)
 
-    storage().delete(:filesystem, file_system_id)
-  end
-
-  defp storage() do
-    Livebook.Storage.current()
+    Livebook.Storage.delete(:filesystem, file_system_id)
   end
 
   defp storage_to_fs(%{type: "s3"} = config) do
@@ -230,7 +226,7 @@ defmodule Livebook.Settings do
   """
   @spec set_default_file_system(file_system_id()) :: :ok
   def set_default_file_system(file_system_id) do
-    storage().insert(:settings, "global", default_file_system_id: file_system_id)
+    Livebook.Storage.insert(:settings, "global", default_file_system_id: file_system_id)
   end
 
   @doc """
@@ -238,7 +234,7 @@ defmodule Livebook.Settings do
   """
   @spec default_file_system() :: Filesystem.t()
   def default_file_system() do
-    case storage().fetch(:filesystem, default_file_system_id()) do
+    case Livebook.Storage.fetch(:filesystem, default_file_system_id()) do
       {:ok, file} -> storage_to_fs(file)
       :error -> Livebook.Config.local_file_system()
     end
@@ -249,7 +245,7 @@ defmodule Livebook.Settings do
   """
   @spec default_file_system_id() :: file_system_id()
   def default_file_system_id() do
-    case storage().fetch_key(:settings, "global", :default_file_system_id) do
+    case Livebook.Storage.fetch_key(:settings, "global", :default_file_system_id) do
       {:ok, default_file_system_id} -> default_file_system_id
       :error -> "local"
     end
diff --git a/lib/livebook/storage.ex b/lib/livebook/storage.ex
index e9ec97586..ae0645655 100644
--- a/lib/livebook/storage.ex
+++ b/lib/livebook/storage.ex
@@ -1,8 +1,18 @@
 defmodule Livebook.Storage do
-  @moduledoc """
-  Behaviour defining an interface for storing arbitrary data in
-  [Entity-Attribute-Value](https://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model) fashion.
-  """
+  @moduledoc false
+
+  # Storage for arbitrary data in [Entity-Attribute-Value](https://en.wikipedia.org/wiki/Entity%E2%80%93attribute%E2%80%93value_model)
+  # fashion.
+  #
+  # The storage uses an ETS table and synchronizes all the changes to
+  # a file, so they are restored when the application is started again.
+  #
+  # `insert` and `delete` operations are supposed to be called using a GenServer
+  # while all the lookups can be performed by directly accessing the named table.
+
+  use GenServer
+
+  require Logger
 
   @type namespace :: atom()
   @type entity_id :: binary()
@@ -22,38 +32,69 @@ defmodule Livebook.Storage do
   end
 
   @doc """
-  Returns all values in namespace.
-
-      all(:filesystem)
-      [%{id: "rand-id", type: "s3", bucket_url: "/...", secret: "abc", access_key: "xyz"}]
-
+  Starts the storage process.
   """
-  @callback all(namespace()) :: [entity()]
+  @spec start_link(keyword()) :: GenServer.on_start()
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
 
   @doc """
-  Delegate for `c:all/1`.
+  Returns all values in namespace.
+
+  ## Examples
+
+      Livebook.Storage.all(:filesystem)
+      #=> [%{id: "rand-id", type: "s3", bucket_url: "/...", secret: "abc", access_key: "xyz"}]
+
   """
-  def all(namespace), do: current().all(namespace)
+  @spec all(namespace()) :: [entity()]
+  def all(namespace) do
+    table_name()
+    |> :ets.match({{namespace, :"$1"}, :"$2", :"$3", :_})
+    |> Enum.group_by(
+      fn [entity_id, _attr, _val] -> entity_id end,
+      fn [_id, attr, val] -> {attr, val} end
+    )
+    |> Enum.map(fn {entity_id, attributes} ->
+      attributes
+      |> Map.new()
+      |> Map.put(:id, entity_id)
+    end)
+  end
 
   @doc """
   Returns a map identified by `entity_id` in `namespace`.
 
-      fetch(:filesystem, "rand-id")
+  ## Examples
+
+      Livebook.Storage.fetch(:filesystem, "rand-id")
       #=> {:ok, %{id: "rand-id", type: "s3", bucket_url: "/...", secret: "abc", access_key: "xyz"}}
 
   """
-  @callback fetch(namespace(), entity_id()) :: {:ok, entity()} | :error
+  @spec fetch(namespace(), entity_id()) :: {:ok, entity()} | :error
+  def fetch(namespace, entity_id) do
+    table_name()
+    |> :ets.lookup({namespace, entity_id})
+    |> case do
+      [] ->
+        :error
 
-  @doc """
-  Delegate for `c:fetch/2`.
-  """
-  def fetch(namespace, id), do: current().fetch(namespace, id)
+      entries ->
+        entries
+        |> Enum.map(fn {_key, attr, val, _timestamp} -> {attr, val} end)
+        |> Map.new()
+        |> Map.put(:id, entity_id)
+        |> then(&{:ok, &1})
+    end
+  end
 
   @doc """
   Raising delegate for `c:fetch/2`.
   """
+  @spec fetch!(namespace(), entity_id()) :: entity()
   def fetch!(namespace, id) do
-    case current().fetch(namespace, id) do
+    case fetch(namespace, id) do
       {:ok, entity} -> entity
       :error -> raise NotFoundError, namespace: namespace, id: id
     end
@@ -62,47 +103,144 @@ defmodule Livebook.Storage do
   @doc """
   Returns the value for a given `namespace`-`entity_id`-`attribute`.
 
-      fetch_key(:filesystem, "rand-id", :type)
+  ## Examples
+
+      Livebook.Storage.fetch_key(:filesystem, "rand-id", :type)
       #=> {:ok, "s3"}
 
   """
-  @callback fetch_key(namespace(), entity_id(), attribute()) :: {:ok, value()} | :error
+  @spec fetch_key(namespace(), entity_id(), attribute()) :: {:ok, value()} | :error
+  def fetch_key(namespace, entity_id, key) do
+    table_name()
+    |> :ets.match({{namespace, entity_id}, key, :"$1", :_})
+    |> case do
+      [[value]] -> {:ok, value}
+      [] -> :error
+    end
+  end
 
   @doc """
-  Delegate for `c:fetch_key/3`.
+  Inserts given list of attribute-value pairs to a entity belonging to
+  specified namespace.
   """
-  def fetch_key(namespace, id, attribute), do: current().fetch_key(namespace, id, attribute)
-
-  @doc """
-  Inserts given list of attribute-value paris to a entity belonging to specified namespace.
-  """
-  @callback insert(namespace(), entity_id(), [{attribute(), value()}]) :: :ok
-
-  @doc """
-  Delegate for `c:insert/3`.
-  """
-  def insert(namespace, id, attributes), do: current().insert(namespace, id, attributes)
+  @spec insert(namespace(), entity_id(), [{attribute(), value()}]) :: :ok
+  def insert(namespace, entity_id, attributes) do
+    GenServer.call(__MODULE__, {:insert, namespace, entity_id, attributes})
+  end
 
   @doc """
   Deletes an entity of given id from given namespace.
   """
-  @callback delete(namespace(), entity_id()) :: :ok
-
-  @doc """
-  Delegate for `c:delete/2`.
-  """
-  def delete(namespace, id), do: current().delete(namespace, id)
+  @spec delete(namespace(), entity_id()) :: :ok
+  def delete(namespace, entity_id) do
+    GenServer.call(__MODULE__, {:delete, namespace, entity_id})
+  end
 
   @doc """
   Deletes an attribute from given entity.
   """
-  @callback delete_key(namespace(), entity_id(), attribute()) :: :ok
+  @spec delete_key(namespace(), entity_id(), attribute()) :: :ok
+  def delete_key(namespace, entity_id, key) do
+    GenServer.call(__MODULE__, {:delete_key, namespace, entity_id, key})
+  end
 
   @doc """
-  Delegate for `c:delete_key/3`.
+  Returns file path where the data is persisted.
   """
-  def delete_key(namespace, id, attribute), do: current().delete_key(namespace, id, attribute)
+  @spec config_file_path() :: Path.t()
+  def config_file_path() do
+    Path.join([Livebook.Config.data_path(), "livebook_config.ets"])
+  end
 
-  @spec current() :: module()
-  def current(), do: Application.fetch_env!(:livebook, :storage)
+  @doc """
+  Synchronously awaits for all prior changes to be processed.
+  """
+  @spec sync() :: :ok
+  def sync() do
+    GenServer.call(__MODULE__, :sync)
+  end
+
+  @impl true
+  def init(_opts) do
+    # Make sure that this process does not terminate abruptly
+    # in case it is persisting to disk. terminate/2 is still a no-op.
+    Process.flag(:trap_exit, true)
+
+    table = load_or_create_table()
+    :persistent_term.put(__MODULE__, table)
+
+    {:ok, %{table: table}}
+  end
+
+  @impl true
+  def handle_call(:sync, _from, state) do
+    {:reply, :ok, state}
+  end
+
+  @impl true
+  def handle_call({:insert, namespace, entity_id, attributes}, _from, %{table: table} = state) do
+    keys_to_delete = Enum.map(attributes, fn {key, _val} -> key end)
+
+    delete_keys(table, namespace, entity_id, keys_to_delete)
+
+    timestamp = System.os_time(:millisecond)
+
+    attributes =
+      Enum.map(attributes, fn {attr, val} ->
+        {{namespace, entity_id}, attr, val, timestamp}
+      end)
+
+    :ets.insert(table, attributes)
+    {:reply, :ok, state, {:continue, :save_to_file}}
+  end
+
+  @impl true
+  def handle_call({:delete, namespace, entity_id}, _from, %{table: table} = state) do
+    :ets.delete(table, {namespace, entity_id})
+    {:reply, :ok, state, {:continue, :save_to_file}}
+  end
+
+  @impl true
+  def handle_call({:delete_key, namespace, entity_id, key}, _from, %{table: table} = state) do
+    delete_keys(table, namespace, entity_id, [key])
+    {:reply, :ok, state, {:continue, :save_to_file}}
+  end
+
+  @impl true
+  def handle_continue(:save_to_file, %{table: table} = state) do
+    file_path = String.to_charlist(config_file_path())
+    :ok = :ets.tab2file(table, file_path)
+    {:noreply, state}
+  end
+
+  defp table_name(), do: :persistent_term.get(__MODULE__)
+
+  defp load_or_create_table() do
+    path = config_file_path()
+
+    path
+    |> String.to_charlist()
+    |> :ets.file2tab()
+    |> case do
+      {:ok, tab} ->
+        Logger.info("Reading storage from #{path}")
+        tab
+
+      {:error, reason} ->
+        case reason do
+          {:read_error, {:file_error, _, :enoent}} -> :ok
+          _ -> Logger.warning("Could not open up #{config_file_path()}: #{inspect(reason)}")
+        end
+
+        :ets.new(__MODULE__, [:protected, :duplicate_bag])
+    end
+  end
+
+  defp delete_keys(table, namespace, entity_id, keys) do
+    match_head = {{namespace, entity_id}, :"$1", :_, :_}
+
+    guards = Enum.map(keys, &{:==, :"$1", &1})
+
+    :ets.select_delete(table, [{match_head, guards, [true]}])
+  end
 end
diff --git a/lib/livebook/storage/ets.ex b/lib/livebook/storage/ets.ex
deleted file mode 100644
index f40984f5e..000000000
--- a/lib/livebook/storage/ets.ex
+++ /dev/null
@@ -1,171 +0,0 @@
-defmodule Livebook.Storage.Ets do
-  @moduledoc """
-  Ets implementation of `Livebook.Storage` behaviour.
-
-  The module is supposed to be started just once as it
-  is responsible for managing a named ets table.
-
-  `insert` and `delete` operations are supposed to be called using a GenServer
-  while all the lookups can be performed by directly accessing the named table.
-  """
-  @behaviour Livebook.Storage
-
-  require Logger
-  use GenServer
-
-  @impl Livebook.Storage
-  def all(namespace) do
-    table_name()
-    |> :ets.match({{namespace, :"$1"}, :"$2", :"$3", :_})
-    |> Enum.group_by(
-      fn [entity_id, _attr, _val] -> entity_id end,
-      fn [_id, attr, val] -> {attr, val} end
-    )
-    |> Enum.map(fn {entity_id, attributes} ->
-      attributes
-      |> Map.new()
-      |> Map.put(:id, entity_id)
-    end)
-  end
-
-  @impl Livebook.Storage
-  def fetch(namespace, entity_id) do
-    table_name()
-    |> :ets.lookup({namespace, entity_id})
-    |> case do
-      [] ->
-        :error
-
-      entries ->
-        entries
-        |> Enum.map(fn {_key, attr, val, _timestamp} -> {attr, val} end)
-        |> Map.new()
-        |> Map.put(:id, entity_id)
-        |> then(&{:ok, &1})
-    end
-  end
-
-  @impl Livebook.Storage
-  def fetch_key(namespace, entity_id, key) do
-    table_name()
-    |> :ets.match({{namespace, entity_id}, key, :"$1", :_})
-    |> case do
-      [[value]] -> {:ok, value}
-      [] -> :error
-    end
-  end
-
-  @spec config_file_path() :: Path.t()
-  def config_file_path() do
-    Path.join([Livebook.Config.data_path(), "livebook_config.ets"])
-  end
-
-  @spec sync() :: :ok
-  def sync() do
-    GenServer.call(__MODULE__, :sync)
-  end
-
-  @impl Livebook.Storage
-  def insert(namespace, entity_id, attributes) do
-    GenServer.call(__MODULE__, {:insert, namespace, entity_id, attributes})
-  end
-
-  @impl Livebook.Storage
-  def delete(namespace, entity_id) do
-    GenServer.call(__MODULE__, {:delete, namespace, entity_id})
-  end
-
-  @impl Livebook.Storage
-  def delete_key(namespace, entity_id, key) do
-    GenServer.call(__MODULE__, {:delete_key, namespace, entity_id, key})
-  end
-
-  @spec start_link(keyword()) :: GenServer.on_start()
-  def start_link(opts) do
-    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
-  end
-
-  @impl GenServer
-  def init(_opts) do
-    # Make sure that this process does not terminate abruptly
-    # in case it is persisting to disk. terminate/2 is still a no-op.
-    Process.flag(:trap_exit, true)
-
-    table = load_or_create_table()
-    :persistent_term.put(__MODULE__, table)
-
-    {:ok, %{table: table}}
-  end
-
-  @impl GenServer
-  def handle_call(:sync, _from, state) do
-    {:reply, :ok, state}
-  end
-
-  @impl GenServer
-  def handle_call({:insert, namespace, entity_id, attributes}, _from, %{table: table} = state) do
-    keys_to_delete = Enum.map(attributes, fn {key, _val} -> key end)
-
-    delete_keys(table, namespace, entity_id, keys_to_delete)
-
-    timestamp = System.os_time(:millisecond)
-
-    attributes =
-      Enum.map(attributes, fn {attr, val} ->
-        {{namespace, entity_id}, attr, val, timestamp}
-      end)
-
-    :ets.insert(table, attributes)
-    {:reply, :ok, state, {:continue, :save_to_file}}
-  end
-
-  @impl GenServer
-  def handle_call({:delete, namespace, entity_id}, _from, %{table: table} = state) do
-    :ets.delete(table, {namespace, entity_id})
-    {:reply, :ok, state, {:continue, :save_to_file}}
-  end
-
-  @impl GenServer
-  def handle_call({:delete_key, namespace, entity_id, key}, _from, %{table: table} = state) do
-    delete_keys(table, namespace, entity_id, [key])
-    {:reply, :ok, state, {:continue, :save_to_file}}
-  end
-
-  @impl GenServer
-  def handle_continue(:save_to_file, %{table: table} = state) do
-    file_path = String.to_charlist(config_file_path())
-    :ok = :ets.tab2file(table, file_path)
-    {:noreply, state}
-  end
-
-  defp table_name(), do: :persistent_term.get(__MODULE__)
-
-  defp load_or_create_table() do
-    path = config_file_path()
-
-    path
-    |> String.to_charlist()
-    |> :ets.file2tab()
-    |> case do
-      {:ok, tab} ->
-        Logger.info("Reading storage from #{path}")
-        tab
-
-      {:error, reason} ->
-        case reason do
-          {:read_error, {:file_error, _, :enoent}} -> :ok
-          _ -> Logger.warning("Could not open up #{config_file_path()}: #{inspect(reason)}")
-        end
-
-        :ets.new(__MODULE__, [:protected, :duplicate_bag])
-    end
-  end
-
-  defp delete_keys(table, namespace, entity_id, keys) do
-    match_head = {{namespace, entity_id}, :"$1", :_, :_}
-
-    guards = Enum.map(keys, &{:==, :"$1", &1})
-
-    :ets.select_delete(table, [{match_head, guards, [true]}])
-  end
-end
diff --git a/test/livebook/storage/ets_test.exs b/test/livebook/storage/ets_test.exs
deleted file mode 100644
index 9082c4d85..000000000
--- a/test/livebook/storage/ets_test.exs
+++ /dev/null
@@ -1,125 +0,0 @@
-defmodule Livebook.Storage.EtsTest do
-  use ExUnit.Case, async: true
-
-  alias Livebook.Storage.Ets
-
-  describe "insert/3 and fetch/2" do
-    test "properly inserts a new key-value attribute" do
-      assert :ok = Ets.insert(:insert, "test", key1: "val1", key2: "val2")
-
-      assert {:ok,
-              %{
-                id: "test",
-                key1: "val1",
-                key2: "val2"
-              }} = Ets.fetch(:insert, "test")
-    end
-
-    test "replaces already existing attributes with new values" do
-      assert :ok = Ets.insert(:insert, "replace", key1: "val1", key2: "val2")
-
-      assert {:ok,
-              %{
-                key1: "val1",
-                key2: "val2"
-              }} = Ets.fetch(:insert, "replace")
-
-      assert :ok =
-               Ets.insert(:insert, "replace", key1: "updated_val1", key2: "val2", key3: "val3")
-
-      assert {:ok,
-              %{
-                key1: "updated_val1",
-                key2: "val2",
-                key3: "val3"
-              }} = Ets.fetch(:insert, "replace")
-    end
-  end
-
-  describe "fetch_key/3" do
-    test "reads a given key" do
-      :ok = Ets.insert(:fetch_key, "test", key1: "val1")
-      assert Ets.fetch_key(:fetch_key, "test", :key1) == {:ok, "val1"}
-      assert Ets.fetch_key(:fetch_key, "test", :key2) == :error
-    end
-
-    test "handles nil accordingly" do
-      assert Ets.fetch_key(:fetch_key, "test_nil", :key1) == :error
-      :ok = Ets.insert(:fetch_key, "test_nil", key1: nil)
-      assert Ets.fetch_key(:fetch_key, "test_nil", :key1) == {:ok, nil}
-    end
-  end
-
-  test "fetch/2" do
-    :ok = Ets.insert(:fetch, "test", key1: "val1")
-
-    assert {:ok,
-            %{
-              id: "test",
-              key1: "val1"
-            }} = Ets.fetch(:fetch, "test")
-
-    assert :error = Ets.fetch(:fetch, "unknown")
-  end
-
-  test "delete/2" do
-    :ok = Ets.insert(:delete, "test", key1: "val1")
-
-    assert {:ok, _entity} = Ets.fetch(:delete, "test")
-
-    assert :ok = Ets.delete(:delete, "test")
-
-    assert :error = Ets.fetch(:delete, "test")
-  end
-
-  test "delete_key/3" do
-    :ok = Ets.insert(:delete_key, "test", key1: "val1", key2: "val2")
-
-    assert :ok = Ets.delete_key(:delete_key, "test", :key2)
-
-    assert {:ok, "val1"} = Ets.fetch_key(:delete_key, "test", :key1)
-    assert :error = Ets.fetch_key(:delete_key, "test", :key2)
-  end
-
-  describe "all/1" do
-    test "returns all inserted entities for given namespace" do
-      :ok = Ets.insert(:all, "test1", key1: "val1")
-      :ok = Ets.insert(:all, "test2", key1: "val1")
-
-      {:ok, entity1} = Ets.fetch(:all, "test1")
-      {:ok, entity2} = Ets.fetch(:all, "test2")
-
-      assert [^entity1, ^entity2] = Enum.sort(Ets.all(:all))
-    end
-
-    test "returns an empty list if no entities exist for given namespace" do
-      assert [] = Ets.all(:unknown_namespace)
-    end
-  end
-
-  describe "persistence" do
-    defp read_table_and_lookup(entity) do
-      :ok = Ets.sync()
-
-      {:ok, tab} =
-        Ets.config_file_path()
-        |> String.to_charlist()
-        |> :ets.file2tab()
-
-      :ets.lookup(tab, {:persistence, entity})
-    end
-
-    test "insert triggers saving to file" do
-      :ok = Ets.insert(:persistence, "insert", key: "val")
-
-      assert [_test] = read_table_and_lookup("insert")
-    end
-
-    test "delete triggers saving to file" do
-      :ok = Ets.insert(:persistence, "delete", key: "val")
-      :ok = Ets.delete(:persistence, "delete")
-
-      assert [] = read_table_and_lookup("delete")
-    end
-  end
-end
diff --git a/test/livebook/storage_test.exs b/test/livebook/storage_test.exs
new file mode 100644
index 000000000..899af70ec
--- /dev/null
+++ b/test/livebook/storage_test.exs
@@ -0,0 +1,125 @@
+defmodule Livebook.StorageTest do
+  use ExUnit.Case, async: true
+
+  alias Livebook.Storage
+
+  describe "insert/3 and fetch/2" do
+    test "properly inserts a new key-value attribute" do
+      assert :ok = Storage.insert(:insert, "test", key1: "val1", key2: "val2")
+
+      assert {:ok,
+              %{
+                id: "test",
+                key1: "val1",
+                key2: "val2"
+              }} = Storage.fetch(:insert, "test")
+    end
+
+    test "replaces already existing attributes with new values" do
+      assert :ok = Storage.insert(:insert, "replace", key1: "val1", key2: "val2")
+
+      assert {:ok,
+              %{
+                key1: "val1",
+                key2: "val2"
+              }} = Storage.fetch(:insert, "replace")
+
+      assert :ok =
+               Storage.insert(:insert, "replace", key1: "updated_val1", key2: "val2", key3: "val3")
+
+      assert {:ok,
+              %{
+                key1: "updated_val1",
+                key2: "val2",
+                key3: "val3"
+              }} = Storage.fetch(:insert, "replace")
+    end
+  end
+
+  describe "fetch_key/3" do
+    test "reads a given key" do
+      :ok = Storage.insert(:fetch_key, "test", key1: "val1")
+      assert Storage.fetch_key(:fetch_key, "test", :key1) == {:ok, "val1"}
+      assert Storage.fetch_key(:fetch_key, "test", :key2) == :error
+    end
+
+    test "handles nil accordingly" do
+      assert Storage.fetch_key(:fetch_key, "test_nil", :key1) == :error
+      :ok = Storage.insert(:fetch_key, "test_nil", key1: nil)
+      assert Storage.fetch_key(:fetch_key, "test_nil", :key1) == {:ok, nil}
+    end
+  end
+
+  test "fetch/2" do
+    :ok = Storage.insert(:fetch, "test", key1: "val1")
+
+    assert {:ok,
+            %{
+              id: "test",
+              key1: "val1"
+            }} = Storage.fetch(:fetch, "test")
+
+    assert :error = Storage.fetch(:fetch, "unknown")
+  end
+
+  test "delete/2" do
+    :ok = Storage.insert(:delete, "test", key1: "val1")
+
+    assert {:ok, _entity} = Storage.fetch(:delete, "test")
+
+    assert :ok = Storage.delete(:delete, "test")
+
+    assert :error = Storage.fetch(:delete, "test")
+  end
+
+  test "delete_key/3" do
+    :ok = Storage.insert(:delete_key, "test", key1: "val1", key2: "val2")
+
+    assert :ok = Storage.delete_key(:delete_key, "test", :key2)
+
+    assert {:ok, "val1"} = Storage.fetch_key(:delete_key, "test", :key1)
+    assert :error = Storage.fetch_key(:delete_key, "test", :key2)
+  end
+
+  describe "all/1" do
+    test "returns all inserted entities for given namespace" do
+      :ok = Storage.insert(:all, "test1", key1: "val1")
+      :ok = Storage.insert(:all, "test2", key1: "val1")
+
+      {:ok, entity1} = Storage.fetch(:all, "test1")
+      {:ok, entity2} = Storage.fetch(:all, "test2")
+
+      assert [^entity1, ^entity2] = Enum.sort(Storage.all(:all))
+    end
+
+    test "returns an empty list if no entities exist for given namespace" do
+      assert [] = Storage.all(:unknown_namespace)
+    end
+  end
+
+  describe "persistence" do
+    defp read_table_and_lookup(entity) do
+      :ok = Storage.sync()
+
+      {:ok, tab} =
+        Storage.config_file_path()
+        |> String.to_charlist()
+        |> :ets.file2tab()
+
+      :ets.lookup(tab, {:persistence, entity})
+    end
+
+    test "insert triggers saving to file" do
+      :ok = Storage.insert(:persistence, "insert", key: "val")
+
+      assert [_test] = read_table_and_lookup("insert")
+    end
+
+    test "delete triggers saving to file" do
+      :ok = Storage.insert(:persistence, "delete", key: "val")
+      :ok = Storage.delete(:persistence, "delete")
+
+      assert [] = read_table_and_lookup("delete")
+    end
+  end
+end