diff --git a/.formatter.exs b/.formatter.exs
index 048ad18..1360534 100644
--- a/.formatter.exs
+++ b/.formatter.exs
@@ -1,4 +1,4 @@
-locals_without_parens = [field: 2, field: 3, parameter: 1, plugin: 1, plugin: 2]
+locals_without_parens = [field: 2, field: 3, parameter: 1, parameter: 2, plugin: 1, plugin: 2]
 
 [
   inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"],
diff --git a/guides/plugins/reflection.md b/guides/plugins/reflection.md
index a51d30a..6f72f90 100644
--- a/guides/plugins/reflection.md
+++ b/guides/plugins/reflection.md
@@ -21,7 +21,7 @@ defmodule Guides.Plugins.Reflection do
         |> Enum.to_list()
 
       def __typed_structor__(:fields), do: unquote(fields)
-      def __typed_structor__(:parameters), do: unquote(definition.parameters)
+      def __typed_structor__(:parameters), do: Enum.map(unquote(definition.parameters), &Keyword.fetch!(&1, :name))
       def __typed_structor__(:enforced_fields), do: unquote(enforced_fields)
 
       for field <- definition.fields do
diff --git a/lib/typed_structor.ex b/lib/typed_structor.ex
index c2959a4..8db43f8 100644
--- a/lib/typed_structor.ex
+++ b/lib/typed_structor.ex
@@ -91,7 +91,8 @@ defmodule TypedStructor do
 
       # create a lexical scope
       try do
-        import TypedStructor, only: [field: 2, field: 3, parameter: 1, plugin: 1, plugin: 2]
+        import TypedStructor,
+          only: [field: 2, field: 3, parameter: 1, parameter: 2, plugin: 1, plugin: 2]
 
         unquote(register_global_plugins())
 
@@ -136,6 +137,7 @@ defmodule TypedStructor do
   defp register_global_plugins do
     :typed_structor
     |> Application.get_env(:plugins, [])
+    |> List.wrap()
     |> Enum.map(fn
       {plugin, opts} when is_atom(plugin) and is_list(opts) ->
         {plugin, opts}
@@ -206,14 +208,17 @@ defmodule TypedStructor do
 
       fied :number, int # not int()
   """
-  defmacro parameter(name) when is_atom(name) do
+  defmacro parameter(name, opts \\ [])
+
+  defmacro parameter(name, opts) when is_atom(name) and is_list(opts) do
     quote do
-      @__ts_struct_parameters__ unquote(name)
+      @__ts_struct_parameters__ Keyword.merge(unquote(opts), name: unquote(name))
     end
   end
 
-  defmacro parameter(name) do
-    raise ArgumentError, "expected an atom, got: #{inspect(name)}"
+  defmacro parameter(name, opts) do
+    raise ArgumentError,
+          "name must be an atom and opts must be a list, got: #{inspect(name)} and #{inspect(opts)}"
   end
 
   @doc """
@@ -285,7 +290,15 @@ defmodule TypedStructor do
 
       type_name = Keyword.get(@__ts_options__, :type_name, :t)
 
-      parameters = Enum.map(@__ts_definition__.parameters, &Macro.var(&1, __MODULE__))
+      parameters =
+        Enum.map(
+          @__ts_definition__.parameters,
+          fn parameter ->
+            parameter
+            |> Keyword.fetch!(:name)
+            |> Macro.var(__MODULE__)
+          end
+        )
 
       case Keyword.get(@__ts_options__, :type_kind, :type) do
         :type ->
diff --git a/lib/typed_structor/definition.ex b/lib/typed_structor/definition.ex
index 389e614..7911142 100644
--- a/lib/typed_structor/definition.ex
+++ b/lib/typed_structor/definition.ex
@@ -7,7 +7,7 @@ defmodule TypedStructor.Definition do
   @type t() :: %__MODULE__{
           options: Keyword.t(),
           fields: [Keyword.t()],
-          parameters: [atom()]
+          parameters: [Keyword.t()]
         }
 
   defstruct [:options, :fields, :parameters]
diff --git a/test/config_test.exs b/test/config_test.exs
index e877976..d8534be 100644
--- a/test/config_test.exs
+++ b/test/config_test.exs
@@ -84,7 +84,7 @@ defmodule ConfigTest do
   end
 
   defp set_plugins_config(plugins) do
-    previous_value = Application.get_env(:typed_structor, :plugins)
+    previous_value = Application.get_env(:typed_structor, :plugins, [])
     Application.put_env(:typed_structor, :plugins, plugins)
     on_exit(fn -> Application.put_env(:typed_structor, :plugins, previous_value) end)
   end
diff --git a/test/support/test_case.ex b/test/support/test_case.ex
index 4d5347c..d462b38 100644
--- a/test/support/test_case.ex
+++ b/test/support/test_case.ex
@@ -30,7 +30,7 @@ defmodule TypedStructor.TestCase do
       |> Macro.expand(__CALLER__)
       |> then(&Module.concat(__CALLER__.module, &1))
 
-    code = Keyword.fetch(options, :do)
+    code = Keyword.fetch!(options, :do)
 
     content =
       """
@@ -60,14 +60,14 @@ defmodule TypedStructor.TestCase do
   def __with_file__(%{tmp_dir: dir}, {module_name, content}, fun) when is_function(fun, 0) do
     path = Path.join([dir, Atom.to_string(module_name)])
 
-    try do
-      File.write!(path, content)
-      compile_file!(path, dir)
+    File.write!(path, content)
+    mods = compile_file!(path, dir)
 
+    try do
       fun.()
     after
       File.rm!(path)
-      cleanup_modules([module_name], dir)
+      cleanup_modules(mods, dir)
     end
   end
 
@@ -139,7 +139,7 @@ defmodule TypedStructor.TestCase do
     module
     |> Code.Typespec.fetch_types()
     |> case do
-      :error -> refute "Failed to fetch types for module #{module}"
+      :error -> flunk("Failed to fetch types for module #{module}")
       {:ok, types} -> types
     end
   end
@@ -150,18 +150,26 @@ defmodule TypedStructor.TestCase do
   def fetch_doc!(module, :moduledoc) when is_atom(module) do
     case Code.fetch_docs(module) do
       {:docs_v1, _, :elixir, _, %{"en" => doc}, _, _} -> doc
-      _ -> refute "Failed to fetch moduledoc for #{module}"
+      _ -> flunk("Failed to fetch moduledoc for #{module}")
     end
   end
 
   def fetch_doc!(module, {type, name, arity}) when is_atom(module) do
-    with(
-      {:docs_v1, _, :elixir, _, _, _, docs} <- Code.fetch_docs(module),
-      {_, _, _, %{"en" => doc}, _} <- List.keyfind(docs, {type, name, arity}, 0)
-    ) do
-      doc
-    else
-      _other -> refute "Failed to fetch doc for #{inspect({type, name, arity})} at #{module}"
+    docs =
+      case Code.fetch_docs(module) do
+        {:docs_v1, _, :elixir, _, _, _, docs} -> docs
+        {:error, reason} -> flunk("Failed to fetch doc for #{module}: #{inspect(reason)}")
+      end
+
+    case List.keyfind(docs, {type, name, arity}, 0) do
+      nil ->
+        flunk("""
+        Failed to fetch doc for #{inspect({type, name, arity})} at #{module}, docs:
+        #{Enum.map_join(docs, "  \n", fn doc -> inspect(elem(doc, 0)) end)}
+        """)
+
+      {_, _, _, %{"en" => doc}, _} ->
+        doc
     end
   end
 
@@ -174,7 +182,7 @@ defmodule TypedStructor.TestCase do
     expected_types = format_types(expected)
 
     if String.length(String.trim(expected_types)) === 0 do
-      refute "Expected types are empty: #{inspect(expected)}"
+      flunk("Expected types are empty: #{inspect(expected)}")
     end
 
     assert expected_types == format_types(actual)
diff --git a/test/typed_structor_test.exs b/test/typed_structor_test.exs
index 1751942..3a31f26 100644
--- a/test/typed_structor_test.exs
+++ b/test/typed_structor_test.exs
@@ -379,15 +379,17 @@ defmodule TypedStructorTest do
     end
 
     test "raises an error when the parameter is not a atom" do
-      assert_raise ArgumentError, ~r[expected an atom, got: "age"], fn ->
-        defmodule Struct do
-          use TypedStructor
-
-          typed_structor do
-            parameter "age"
-          end
-        end
-      end
+      assert_raise ArgumentError,
+                   ~r|name must be an atom and opts must be a list|,
+                   fn ->
+                     defmodule Struct do
+                       use TypedStructor
+
+                       typed_structor do
+                         parameter "age"
+                       end
+                     end
+                   end
     end
   end