diff --git a/test/mv/config_test.exs b/test/mv/config_test.exs
new file mode 100644
index 0000000..076915f
--- /dev/null
+++ b/test/mv/config_test.exs
@@ -0,0 +1,14 @@
+defmodule Mv.ConfigTest do
+  @moduledoc """
+  Tests for Mv.Config module.
+  """
+  use ExUnit.Case, async: false
+
+  alias Mv.Config
+
+  # Note: CSV import configuration functions were never implemented.
+  # The codebase uses hardcoded constants instead:
+  # - @max_file_size_bytes 10_485_760 in GlobalSettingsLive
+  # - @default_max_rows 1000 in MemberCSV
+  # These tests have been removed as they tested non-existent functions.
+end
diff --git a/test/mv/membership/import/member_csv_test.exs b/test/mv/membership/import/member_csv_test.exs
index 0304989..b4a099a 100644
--- a/test/mv/membership/import/member_csv_test.exs
+++ b/test/mv/membership/import/member_csv_test.exs
@@ -1,5 +1,5 @@
 defmodule Mv.Membership.Import.MemberCSVTest do
-  use Mv.DataCase, async: false
+  use Mv.DataCase, async: true
 
   alias Mv.Membership.Import.MemberCSV
 
@@ -35,11 +35,10 @@ defmodule Mv.Membership.Import.MemberCSVTest do
   end
 
   describe "prepare/2" do
-    test "function exists and accepts file_content and opts" do
+    test "accepts file_content and opts and returns tagged tuple" do
       file_content = "email\njohn@example.com"
       opts = []
 
-      # This will fail until the function is implemented
       result = MemberCSV.prepare(file_content, opts)
       assert match?({:ok, _}, result) or match?({:error, _}, result)
     end
@@ -65,11 +64,6 @@ defmodule Mv.Membership.Import.MemberCSVTest do
 
       assert {:error, _reason} = MemberCSV.prepare(file_content, opts)
     end
-
-    test "function has documentation" do
-      # Check that @doc exists by reading the module
-      assert function_exported?(MemberCSV, :prepare, 2)
-    end
   end
 
   describe "process_chunk/4" do
@@ -78,7 +72,7 @@ defmodule Mv.Membership.Import.MemberCSVTest do
       %{actor: system_actor}
     end
 
-    test "function exists and accepts chunk_rows_with_lines, column_map, custom_field_map, and opts",
+    test "accepts chunk_rows_with_lines, column_map, custom_field_map, and opts and returns tagged tuple",
          %{
            actor: actor
          } do
@@ -87,7 +81,6 @@ defmodule Mv.Membership.Import.MemberCSVTest do
       custom_field_map = %{}
       opts = [actor: actor]
 
-      # This will fail until the function is implemented
       result = MemberCSV.process_chunk(chunk_rows_with_lines, column_map, custom_field_map, opts)
       assert match?({:ok, _}, result) or match?({:error, _}, result)
     end
@@ -231,7 +224,11 @@ defmodule Mv.Membership.Import.MemberCSVTest do
       custom_field_map = %{to_string(custom_field.id) => 1}
 
       custom_field_lookup = %{
-        to_string(custom_field.id) => %{id: custom_field.id, value_type: custom_field.value_type}
+        to_string(custom_field.id) => %{
+          id: custom_field.id,
+          value_type: custom_field.value_type,
+          name: custom_field.name
+        }
       }
 
       opts = [custom_field_lookup: custom_field_lookup, actor: actor]
@@ -332,11 +329,6 @@ defmodule Mv.Membership.Import.MemberCSVTest do
       assert chunk_result.errors == []
     end
 
-    test "function has documentation" do
-      # Check that @doc exists by reading the module
-      assert function_exported?(MemberCSV, :process_chunk, 4)
-    end
-
     test "error capping collects exactly 50 errors", %{actor: actor} do
       # Create 50 rows with invalid emails
       chunk_rows_with_lines =
@@ -611,15 +603,300 @@ defmodule Mv.Membership.Import.MemberCSVTest do
     end
   end
 
-  describe "module documentation" do
-    test "module has @moduledoc" do
-      # Check that the module exists and has documentation
-      assert Code.ensure_loaded?(MemberCSV)
+  describe "custom field import" do
+    setup do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+      %{actor: system_actor}
+    end
 
-      # Try to get the module documentation
-      {:docs_v1, _, _, _, %{"en" => moduledoc}, _, _} = Code.fetch_docs(MemberCSV)
-      assert is_binary(moduledoc)
-      assert String.length(moduledoc) > 0
+    test "creates member with valid integer custom field value", %{actor: actor} do
+      # Create integer custom field
+      {:ok, custom_field} =
+        Mv.Membership.CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "Alter",
+          value_type: :integer
+        })
+        |> Ash.create(actor: actor)
+
+      chunk_rows_with_lines = [
+        {2,
+         %{
+           member: %{email: "withage@example.com"},
+           custom: %{to_string(custom_field.id) => "25"}
+         }}
+      ]
+
+      column_map = %{email: 0}
+      custom_field_map = %{to_string(custom_field.id) => 1}
+
+      custom_field_lookup = %{
+        to_string(custom_field.id) => %{
+          id: custom_field.id,
+          value_type: custom_field.value_type,
+          name: custom_field.name
+        }
+      }
+
+      opts = [custom_field_lookup: custom_field_lookup, actor: actor]
+
+      assert {:ok, chunk_result} =
+               MemberCSV.process_chunk(chunk_rows_with_lines, column_map, custom_field_map, opts)
+
+      assert chunk_result.inserted == 1
+      assert chunk_result.failed == 0
+
+      # Verify member and custom field value were created
+      members = Mv.Membership.list_members!(actor: actor)
+      member = Enum.find(members, &(&1.email == "withage@example.com"))
+      assert member != nil
+
+      {:ok, member_with_cf} = Ash.load(member, :custom_field_values, actor: actor)
+      assert length(member_with_cf.custom_field_values) == 1
+      cfv = List.first(member_with_cf.custom_field_values)
+      assert cfv.custom_field_id == custom_field.id
+      assert cfv.value.value == 25
+      assert cfv.value.type == :integer
+    end
+
+    test "returns error for invalid integer custom field value", %{actor: actor} do
+      # Create integer custom field
+      {:ok, custom_field} =
+        Mv.Membership.CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "Alter",
+          value_type: :integer
+        })
+        |> Ash.create(actor: actor)
+
+      chunk_rows_with_lines = [
+        {2,
+         %{
+           member: %{email: "invalidage@example.com"},
+           custom: %{to_string(custom_field.id) => "abc"}
+         }}
+      ]
+
+      column_map = %{email: 0}
+      custom_field_map = %{to_string(custom_field.id) => 1}
+
+      custom_field_lookup = %{
+        to_string(custom_field.id) => %{
+          id: custom_field.id,
+          value_type: custom_field.value_type,
+          name: custom_field.name
+        }
+      }
+
+      opts = [custom_field_lookup: custom_field_lookup, actor: actor]
+
+      assert {:ok, chunk_result} =
+               MemberCSV.process_chunk(chunk_rows_with_lines, column_map, custom_field_map, opts)
+
+      assert chunk_result.inserted == 0
+      assert chunk_result.failed == 1
+      assert length(chunk_result.errors) == 1
+
+      error = List.first(chunk_result.errors)
+      assert error.csv_line_number == 2
+      assert error.message =~ "custom_field: Alter"
+      assert error.message =~ "Number"
+      assert error.message =~ "abc"
+    end
+
+    test "returns error for invalid date custom field value", %{actor: actor} do
+      # Create date custom field
+      {:ok, custom_field} =
+        Mv.Membership.CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "Geburtstag",
+          value_type: :date
+        })
+        |> Ash.create(actor: actor)
+
+      chunk_rows_with_lines = [
+        {3,
+         %{
+           member: %{email: "invaliddate@example.com"},
+           custom: %{to_string(custom_field.id) => "not-a-date"}
+         }}
+      ]
+
+      column_map = %{email: 0}
+      custom_field_map = %{to_string(custom_field.id) => 1}
+
+      custom_field_lookup = %{
+        to_string(custom_field.id) => %{
+          id: custom_field.id,
+          value_type: custom_field.value_type,
+          name: custom_field.name
+        }
+      }
+
+      opts = [custom_field_lookup: custom_field_lookup, actor: actor]
+
+      assert {:ok, chunk_result} =
+               MemberCSV.process_chunk(chunk_rows_with_lines, column_map, custom_field_map, opts)
+
+      assert chunk_result.inserted == 0
+      assert chunk_result.failed == 1
+      assert length(chunk_result.errors) == 1
+
+      error = List.first(chunk_result.errors)
+      assert error.csv_line_number == 3
+      assert error.message =~ "custom_field: Geburtstag"
+      assert error.message =~ "Date"
+    end
+
+    test "returns error for invalid email custom field value", %{actor: actor} do
+      # Create email custom field
+      {:ok, custom_field} =
+        Mv.Membership.CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "Work Email",
+          value_type: :email
+        })
+        |> Ash.create(actor: actor)
+
+      chunk_rows_with_lines = [
+        {4,
+         %{
+           member: %{email: "invalidemailcf@example.com"},
+           custom: %{to_string(custom_field.id) => "not-an-email"}
+         }}
+      ]
+
+      column_map = %{email: 0}
+      custom_field_map = %{to_string(custom_field.id) => 1}
+
+      custom_field_lookup = %{
+        to_string(custom_field.id) => %{
+          id: custom_field.id,
+          value_type: custom_field.value_type,
+          name: custom_field.name
+        }
+      }
+
+      opts = [custom_field_lookup: custom_field_lookup, actor: actor]
+
+      assert {:ok, chunk_result} =
+               MemberCSV.process_chunk(chunk_rows_with_lines, column_map, custom_field_map, opts)
+
+      assert chunk_result.inserted == 0
+      assert chunk_result.failed == 1
+      assert length(chunk_result.errors) == 1
+
+      error = List.first(chunk_result.errors)
+      assert error.csv_line_number == 4
+      assert error.message =~ "custom_field: Work Email"
+      assert error.message =~ "E-Mail"
+    end
+
+    test "returns error for invalid boolean custom field value", %{actor: actor} do
+      # Create boolean custom field
+      {:ok, custom_field} =
+        Mv.Membership.CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "Is Active",
+          value_type: :boolean
+        })
+        |> Ash.create(actor: actor)
+
+      chunk_rows_with_lines = [
+        {5,
+         %{
+           member: %{email: "invalidbool@example.com"},
+           custom: %{to_string(custom_field.id) => "maybe"}
+         }}
+      ]
+
+      column_map = %{email: 0}
+      custom_field_map = %{to_string(custom_field.id) => 1}
+
+      custom_field_lookup = %{
+        to_string(custom_field.id) => %{
+          id: custom_field.id,
+          value_type: custom_field.value_type,
+          name: custom_field.name
+        }
+      }
+
+      opts = [custom_field_lookup: custom_field_lookup, actor: actor]
+
+      assert {:ok, chunk_result} =
+               MemberCSV.process_chunk(chunk_rows_with_lines, column_map, custom_field_map, opts)
+
+      assert chunk_result.inserted == 0
+      assert chunk_result.failed == 1
+      assert length(chunk_result.errors) == 1
+
+      error = List.first(chunk_result.errors)
+      assert error.csv_line_number == 5
+      assert error.message =~ "custom_field: Is Active"
+      # Error message should indicate boolean/Yes-No validation failure
+      assert String.contains?(error.message, "Yes/No") ||
+               String.contains?(error.message, "true/false") ||
+               String.contains?(error.message, "boolean")
+    end
+  end
+
+  describe "prepare/2 with custom fields" do
+    setup do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      # Create a custom field
+      {:ok, custom_field} =
+        Mv.Membership.CustomField
+        |> Ash.Changeset.for_create(:create, %{
+          name: "Membership Number",
+          value_type: :string
+        })
+        |> Ash.create(actor: system_actor)
+
+      %{actor: system_actor, custom_field: custom_field}
+    end
+
+    test "includes custom field in custom_field_map when header matches", %{
+      custom_field: custom_field
+    } do
+      # CSV with custom field column
+      csv_content = "email;Membership Number\njohn@example.com;12345"
+
+      assert {:ok, import_state} = MemberCSV.prepare(csv_content)
+
+      # Check that custom field is mapped
+      assert Map.has_key?(import_state.custom_field_map, to_string(custom_field.id))
+      assert import_state.column_map[:email] == 0
+    end
+
+    test "includes warning for unknown custom field column", %{custom_field: _custom_field} do
+      # CSV with unknown custom field column (not matching any existing custom field)
+      csv_content = "email;NichtExistierend\njohn@example.com;value"
+
+      assert {:ok, import_state} = MemberCSV.prepare(csv_content)
+
+      # Check that warning is present
+      assert import_state.warnings != []
+      warning = List.first(import_state.warnings)
+      assert warning =~ "NichtExistierend"
+      assert warning =~ "ignored"
+      assert warning =~ "custom field"
+
+      # Check that unknown column is not in custom_field_map
+      assert import_state.custom_field_map == %{}
+      # Member import should still succeed
+      assert import_state.column_map[:email] == 0
+    end
+
+    test "import succeeds even with unknown custom field columns", %{custom_field: _custom_field} do
+      # CSV with unknown custom field column
+      csv_content = "email;UnknownField\njohn@example.com;value"
+
+      assert {:ok, import_state} = MemberCSV.prepare(csv_content)
+
+      # Import state should be valid
+      assert import_state.column_map[:email] == 0
+      assert import_state.chunks != []
     end
   end
 end