diff --git a/lib/parameter/field.ex b/lib/parameter/field.ex
index bae49c6..507ffec 100644
--- a/lib/parameter/field.ex
+++ b/lib/parameter/field.ex
@@ -172,7 +172,7 @@ defmodule Parameter.Field do
     :ok
   end
 
-  defp function_valid?(_validator, _arity, message) do
-    {:error, message}
+  defp function_valid?(_validator, arity, message) do
+    {:error, "#{message} with #{arity} arity"}
   end
 end
diff --git a/lib/parameter/types.ex b/lib/parameter/types.ex
index 0bde201..b3e8b45 100644
--- a/lib/parameter/types.ex
+++ b/lib/parameter/types.ex
@@ -64,6 +64,7 @@ defmodule Parameter.Types do
 
   @spec assoc_type?(any) :: boolean
   def assoc_type?({type, _}), do: type in @assoc_types
+  def assoc_type?(_), do: false
 
   @types_mod %{
     any: Parameter.Types.Any,
@@ -128,7 +129,7 @@ defmodule Parameter.Types do
   end
 
   def validate({:map, _inner_type}, _values) do
-    {:error, "invalid array type"}
+    {:error, "invalid map type"}
   end
 
   def validate({:has_one, inner_type}, values) when is_map(values) do
diff --git a/lib/parameter/types/boolean.ex b/lib/parameter/types/boolean.ex
index a11e4ad..8ee3c7b 100644
--- a/lib/parameter/types/boolean.ex
+++ b/lib/parameter/types/boolean.ex
@@ -9,9 +9,15 @@ defmodule Parameter.Types.Boolean do
   loads boolean type
 
   ## Examples
+      iex> Parameter.Types.Boolean.load(true)
+      {:ok, true}
+
       iex> Parameter.Types.Boolean.load("true")
       {:ok, true}
 
+      iex> Parameter.Types.Boolean.load("True")
+      {:ok, true}
+
       iex> Parameter.Types.Boolean.load("false")
       {:ok, false}
 
diff --git a/lib/parameter/types/float.ex b/lib/parameter/types/float.ex
index 7508704..f9dd246 100644
--- a/lib/parameter/types/float.ex
+++ b/lib/parameter/types/float.ex
@@ -5,6 +5,25 @@ defmodule Parameter.Types.Float do
 
   use Parameter.Parametrizable
 
+  @doc """
+  loads float type
+
+  ## Examples
+      iex> Parameter.Types.Float.load(1.5)
+      {:ok, 1.5}
+
+      iex> Parameter.Types.Float.load("2.5")
+      {:ok, 2.5}
+
+      iex> Parameter.Types.Float.load(1)
+      {:ok, 1.0}
+
+      iex> Parameter.Types.Float.load("not float")
+      {:error, "invalid float type"}
+
+      iex> Parameter.Types.Float.load(:atom)
+      {:error, "invalid float type"}
+  """
   @impl true
   def load(value) when is_float(value) do
     {:ok, value}
diff --git a/lib/parameter/types/naive_datetime.ex b/lib/parameter/types/naive_datetime.ex
index b2257fd..dc33035 100644
--- a/lib/parameter/types/naive_datetime.ex
+++ b/lib/parameter/types/naive_datetime.ex
@@ -5,6 +5,25 @@ defmodule Parameter.Types.NaiveDateTime do
 
   use Parameter.Parametrizable
 
+  @doc """
+  loads NaiveDateTime type
+
+  ## Examples
+      iex> Parameter.Types.NaiveDateTime.load(~N[2000-01-01 23:00:07])
+      {:ok, ~N[2000-01-01 23:00:07]}
+
+      iex> Parameter.Types.NaiveDateTime.load("2000-01-01 22:00:07")
+      {:ok, ~N[2000-01-01 22:00:07]}
+
+      iex> Parameter.Types.NaiveDateTime.load({{2021, 05, 11}, {22, 30, 10}})
+      {:ok, ~N[2021-05-11 22:30:10]}
+
+      iex> Parameter.Types.NaiveDateTime.load({{2021, 25, 11}, {22, 30, 10}})
+      {:error, "invalid naive_datetime type"}
+
+      iex> Parameter.Types.NaiveDateTime.load("2015-25-23")
+      {:error, "invalid naive_datetime type"}
+  """
   @impl true
   def load(%NaiveDateTime{} = value) do
     {:ok, value}
diff --git a/test/parameter/field_test.exs b/test/parameter/field_test.exs
index 8b1fd05..c76d47b 100644
--- a/test/parameter/field_test.exs
+++ b/test/parameter/field_test.exs
@@ -36,6 +36,30 @@ defmodule Parameter.FieldTest do
       assert {:error, "invalid float type"} == Field.new(opts)
     end
 
+    test "fails if name is not an atom" do
+      opts = [
+        name: "main_address",
+        type: :float,
+        key: "mainAddress",
+        required: true,
+        default: "Hello"
+      ]
+
+      assert {:error, "invalid atom type"} == Field.new(opts)
+    end
+
+    test "fails on invalid function" do
+      opts = [
+        name: :address,
+        type: :float,
+        on_load: fn val -> val end,
+        key: "mainAddress",
+        required: true
+      ]
+
+      assert {:error, "on_load must be a function with 2 arity"} == Field.new(opts)
+    end
+
     test "fails if a default value used at the sametime with load_default and dump_default" do
       opts = [
         name: :main_address,
diff --git a/test/parameter/schema_test.exs b/test/parameter/schema_test.exs
index 5f9f382..3dac565 100644
--- a/test/parameter/schema_test.exs
+++ b/test/parameter/schema_test.exs
@@ -107,6 +107,30 @@ defmodule Parameter.SchemaTest do
     end
   end
 
+  describe "fields/1" do
+    import Parameter.Schema
+
+    param ModuleSchema do
+      field :first_name, :string
+    end
+
+    test "module schema schema fields" do
+      assert [%Parameter.Field{}] = Schema.fields(__MODULE__.ModuleSchema)
+    end
+
+    test "runtime schema fields" do
+      schema =
+        %{
+          first_name: [key: "firstName", type: :string, required: true],
+          address: [required: true, type: {:has_one, %{street: [type: :string, required: true]}}],
+          phones: [type: {:has_many, %{country: [type: :string, required: true]}}]
+        }
+        |> Schema.compile!()
+
+      assert [%Parameter.Field{}, %Parameter.Field{}, %Parameter.Field{}] = Schema.fields(schema)
+    end
+  end
+
   defp from_name(parameters, name) do
     Enum.find(parameters, &(&1.name == name))
   end
diff --git a/test/parameter/types/float_test.exs b/test/parameter/types/float_test.exs
new file mode 100644
index 0000000..c954d59
--- /dev/null
+++ b/test/parameter/types/float_test.exs
@@ -0,0 +1,4 @@
+defmodule Parameter.Types.FloatTest do
+  use ExUnit.Case
+  doctest Parameter.Types.Float
+end
diff --git a/test/parameter/types/naive_datetime_test.exs b/test/parameter/types/naive_datetime_test.exs
new file mode 100644
index 0000000..dfa3aea
--- /dev/null
+++ b/test/parameter/types/naive_datetime_test.exs
@@ -0,0 +1,4 @@
+defmodule Parameter.Types.NaiveDateTimeTest do
+  use ExUnit.Case
+  doctest Parameter.Types.NaiveDateTime
+end
diff --git a/test/parameter/types_test.exs b/test/parameter/types_test.exs
index bed4c59..c9d3dd4 100644
--- a/test/parameter/types_test.exs
+++ b/test/parameter/types_test.exs
@@ -9,6 +9,24 @@ defmodule Parameter.TypesTest do
     enum values: [:user_online, :user_offline]
   end
 
+  test "base_type?/1" do
+    assert Types.base_type?(:any)
+    refute Types.base_type?(:not_type)
+  end
+
+  test "composite_inner_type?/1" do
+    assert Types.composite_inner_type?({:array, :any})
+    assert Types.composite_inner_type?({:map, :not_type})
+    refute Types.composite_inner_type?(:not_type)
+  end
+
+  test "assoc_type?/1" do
+    assert Types.assoc_type?({:has_one, :any})
+    assert Types.assoc_type?({:has_many, :any})
+    refute Types.assoc_type?({:map, :not_type})
+    refute Types.assoc_type?(:not_type)
+  end
+
   describe "load/2" do
     test "load any type" do
       assert Types.load(:any, "Test") == {:ok, "Test"}
@@ -354,5 +372,37 @@ defmodule Parameter.TypesTest do
 
       assert Types.validate({:has_one, :float}, "21") == {:error, "invalid inner data type"}
     end
+
+    test "validate map with inner type" do
+      assert Types.validate({:map, :string}, %{}) == :ok
+      assert Types.validate({:map, :string}, %{key: "value", other_key: "other value"}) == :ok
+
+      assert Types.validate({:map, :string}, %{key: "value", other_key: 22}) ==
+               {:error, "invalid string type"}
+
+      assert Types.validate({:map, :float}, "21") == {:error, "invalid map type"}
+      assert Types.validate({:map, {:array, :float}}, "21") == {:error, "invalid map type"}
+      assert Types.validate({:map, {:array, :float}}, %{k: [1.5]}) == :ok
+    end
+
+    test "validate array with inner type" do
+      assert Types.validate({:array, :string}, []) == :ok
+      assert Types.validate({:array, :string}, ["value", "other value"]) == :ok
+
+      assert Types.validate({:array, :float}, ["value", "other value"]) ==
+               {:error, "invalid float type"}
+
+      assert Types.validate({:array, :float}, "21") == {:error, "invalid array type"}
+      assert Types.validate({:array, {:array, :float}}, "21") == {:error, "invalid array type"}
+      assert Types.validate({:array, {:array, :float}}, [[1.5, 5.5], [1.2]]) == :ok
+    end
+  end
+
+  test "validate!/2" do
+    assert Types.validate!(:any, %{}) == :ok
+
+    assert_raise ArgumentError, "invalid inner data type", fn ->
+      Types.validate!({:has_one, :float}, "21") == {:error, "invalid inner data type"}
+    end
   end
 end