test(vereinfacht): add tests and scope README

- Config, Client, SyncContact, Vereinfacht module tests (no real API)
- vereinfacht_test_README: document test scope

test/mv/config_vereinfacht_test.exs

@@ -0,0 +1,61 @@
+defmodule Mv.ConfigVereinfachtTest do
+  @moduledoc """
+  Tests for Mv.Config Vereinfacht-related helpers.
+  """
+  use Mv.DataCase, async: false
+
+  describe "vereinfacht_env_configured?/0" do
+    test "returns false when no Vereinfacht ENV variables are set" do
+      clear_vereinfacht_env()
+      refute Mv.Config.vereinfacht_env_configured?()
+    end
+
+    test "returns true when VEREINFACHT_API_URL is set" do
+      set_vereinfacht_env("VEREINFACHT_API_URL", "https://api.example.com")
+      assert Mv.Config.vereinfacht_env_configured?()
+    after
+      clear_vereinfacht_env()
+    end
+
+    test "returns true when VEREINFACHT_CLUB_ID is set" do
+      set_vereinfacht_env("VEREINFACHT_CLUB_ID", "2")
+      assert Mv.Config.vereinfacht_env_configured?()
+    after
+      clear_vereinfacht_env()
+    end
+  end
+
+  describe "vereinfacht_configured?/0" do
+    test "returns false when no config is set" do
+      clear_vereinfacht_env()
+      # Settings may have nil for vereinfacht fields
+      refute Mv.Config.vereinfacht_configured?()
+    end
+  end
+
+  describe "vereinfacht_contact_view_url/1" do
+    test "returns nil when API URL is not configured" do
+      clear_vereinfacht_env()
+      assert Mv.Config.vereinfacht_contact_view_url("123") == nil
+    end
+
+    test "returns URL when API URL is set" do
+      set_vereinfacht_env("VEREINFACHT_API_URL", "https://api.example.com/api/v1")
+
+      assert Mv.Config.vereinfacht_contact_view_url("42") ==
+               "https://api.example.com/api/v1/finance-contacts/42"
+    after
+      clear_vereinfacht_env()
+    end
+  end
+
+  defp set_vereinfacht_env(key, value) do
+    System.put_env(key, value)
+  end
+
+  defp clear_vereinfacht_env do
+    System.delete_env("VEREINFACHT_API_URL")
+    System.delete_env("VEREINFACHT_API_KEY")
+    System.delete_env("VEREINFACHT_CLUB_ID")
+  end
+end

test/mv/vereinfacht/changes/sync_contact_test.exs

@@ -0,0 +1,92 @@
+defmodule Mv.Vereinfacht.Changes.SyncContactTest do
+  @moduledoc """
+  Tests for Mv.Vereinfacht.Changes.SyncContact.
+
+  When Vereinfacht is not configured, member create/update should succeed
+  and vereinfacht_contact_id remains nil.
+  """
+  use Mv.DataCase, async: false
+
+  alias Mv.Membership
+
+  setup do
+    clear_vereinfacht_env()
+    :ok
+  end
+
+  describe "member create when Vereinfacht not configured" do
+    test "member is created and vereinfacht_contact_id is nil" do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      attrs = %{
+        first_name: "Sync",
+        last_name: "Test",
+        email: "sync_test_#{System.unique_integer([:positive])}@example.com"
+      }
+
+      assert {:ok, member} = Membership.create_member(attrs, actor: system_actor)
+      assert member.vereinfacht_contact_id == nil
+    end
+  end
+
+  describe "member update when Vereinfacht not configured" do
+    test "member is updated and vereinfacht_contact_id is unchanged" do
+      member = Mv.Fixtures.member_fixture()
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      assert {:ok, updated} =
+               Membership.update_member(member, %{first_name: "Updated"}, actor: system_actor)
+
+      assert updated.vereinfacht_contact_id == nil
+    end
+  end
+
+  describe "when Vereinfacht is configured" do
+    # Regression: after_transaction callback receives 2 args (changeset, result), not 3.
+    # If the callback had arity 3, create_member would raise BadArityError.
+    # Also: Client must send JSON-encoded body (iodata); raw map causes ArgumentError
+    # when the request is sent. With an unreachable URL we get :econnrefused before
+    # that, so this test would not catch the iodata bug; a Bypass/stub server would.
+    test "create_member succeeds and after_transaction runs without error (API may fail)" do
+      set_vereinfacht_env()
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      attrs = %{
+        first_name: "API",
+        last_name: "Test",
+        email: "api_test_#{System.unique_integer([:positive])}@example.com"
+      }
+
+      assert {:ok, member} = Membership.create_member(attrs, actor: system_actor)
+      assert member.id
+      # Sync may fail (e.g. connection refused), so contact_id can stay nil
+    after
+      clear_vereinfacht_env()
+    end
+
+    test "update_member succeeds and after_transaction runs without error (API may fail)" do
+      set_vereinfacht_env()
+      member = Mv.Fixtures.member_fixture()
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      assert {:ok, updated} =
+               Membership.update_member(member, %{first_name: "Updated"}, actor: system_actor)
+
+      assert updated.id == member.id
+    after
+      clear_vereinfacht_env()
+    end
+  end
+
+  defp set_vereinfacht_env do
+    System.put_env("VEREINFACHT_API_URL", "http://127.0.0.1:1/api/v1")
+    System.put_env("VEREINFACHT_API_KEY", "test-key")
+    System.put_env("VEREINFACHT_CLUB_ID", "2")
+  end
+
+  defp clear_vereinfacht_env do
+    System.delete_env("VEREINFACHT_API_URL")
+    System.delete_env("VEREINFACHT_API_KEY")
+    System.delete_env("VEREINFACHT_CLUB_ID")
+  end
+end

test/mv/vereinfacht/client_test.exs

@@ -0,0 +1,50 @@
+defmodule Mv.Vereinfacht.ClientTest do
+  @moduledoc """
+  Tests for Mv.Vereinfacht.Client.
+
+  Only tests the "not configured" path; no real HTTP calls. Config reads from
+  ENV first, then from Settings (DB), so we use DataCase so get_settings() is available.
+  """
+  use Mv.DataCase, async: false
+
+  alias Mv.Vereinfacht.Client
+
+  setup do
+    clear_vereinfacht_env()
+    :ok
+  end
+
+  describe "create_contact/1" do
+    test "returns {:error, :not_configured} when Vereinfacht is not configured" do
+      member = build_member_struct()
+
+      assert Client.create_contact(member) == {:error, :not_configured}
+    end
+  end
+
+  describe "update_contact/2" do
+    test "returns {:error, :not_configured} when Vereinfacht is not configured" do
+      member = build_member_struct()
+
+      assert Client.update_contact("123", member) == {:error, :not_configured}
+    end
+  end
+
+  defp build_member_struct do
+    %{
+      first_name: "Test",
+      last_name: "User",
+      email: "test@example.com",
+      street: "Street 1",
+      house_number: "2",
+      postal_code: "12345",
+      city: "Berlin"
+    }
+  end
+
+  defp clear_vereinfacht_env do
+    System.delete_env("VEREINFACHT_API_URL")
+    System.delete_env("VEREINFACHT_API_KEY")
+    System.delete_env("VEREINFACHT_CLUB_ID")
+  end
+end

test/mv/vereinfacht/vereinfacht_test.exs

@@ -0,0 +1,59 @@
+defmodule Mv.VereinfachtTest do
+  @moduledoc """
+  Tests for Mv.Vereinfacht business logic.
+
+  No real API calls; tests "not configured" path and pure helpers (format_error).
+  """
+  use Mv.DataCase, async: false
+
+  alias Mv.Vereinfacht
+
+  setup do
+    clear_vereinfacht_env()
+    :ok
+  end
+
+  describe "sync_member/1" do
+    test "returns :ok when Vereinfacht is not configured (no-op)" do
+      member = Mv.Fixtures.member_fixture()
+
+      assert Vereinfacht.sync_member(member) == :ok
+    end
+  end
+
+  describe "sync_members_without_contact/0" do
+    test "returns {:error, :not_configured} when Vereinfacht is not configured" do
+      assert Vereinfacht.sync_members_without_contact() == {:error, :not_configured}
+    end
+  end
+
+  describe "format_error/1" do
+    test "formats HTTP error with detail" do
+      assert Vereinfacht.format_error({:http, 422, "The email field is required."}) ==
+               "Vereinfacht: The email field is required."
+    end
+
+    test "formats HTTP error without detail" do
+      assert Vereinfacht.format_error({:http, 500, nil}) ==
+               "Vereinfacht: API error (HTTP 500)."
+    end
+
+    test "formats request_failed" do
+      assert Vereinfacht.format_error({:request_failed, %{reason: :econnrefused}}) ==
+               "Vereinfacht: Request failed (e.g. connection error)."
+    end
+
+    test "formats invalid_response and other terms" do
+      assert Vereinfacht.format_error({:invalid_response, %{}}) ==
+               "Vereinfacht: Invalid API response."
+
+      assert Vereinfacht.format_error(:timeout) == "Vereinfacht: :timeout"
+    end
+  end
+
+  defp clear_vereinfacht_env do
+    System.delete_env("VEREINFACHT_API_URL")
+    System.delete_env("VEREINFACHT_API_KEY")
+    System.delete_env("VEREINFACHT_CLUB_ID")
+  end
+end

test/mv/vereinfacht/vereinfacht_test_README.md

@@ -0,0 +1,29 @@
+# Vereinfacht tests – scope and rationale
+
+## Constraint: no real API in CI
+
+Tests do **not** call the real Vereinfacht API or a shared test endpoint. All tests use dummy data and either:
+
+- Assert behaviour when **Vereinfacht is not configured** (ENV + Settings unset), or  
+- Run the **full Member/User flow** with a **unreachable URL** (e.g. `http://127.0.0.1:1`) so the HTTP client fails fast (e.g. `:econnrefused`) and we only assert that the application path does not crash.
+
+## What the tests cover
+
+| Test file | What it tests | Why it’s enough without an API |
+|-----------|----------------|---------------------------------|
+| **ConfigVereinfachtTest** | `vereinfacht_env_configured?`, `vereinfacht_configured?`, `vereinfacht_contact_view_url` with ENV set/cleared | Pure config logic; no HTTP. |
+| **ClientTest** | `create_contact/1` and `update_contact/2` return `{:error, :not_configured}` when nothing is configured | Ensures the client does not call Req when config is missing. |
+| **VereinfachtTest** | `sync_members_without_contact/0` returns `{:error, :not_configured}` when not configured | Ensures bulk sync is a no-op when config is missing. |
+| **SyncContactTest** | Member create/update with SyncContact change: not configured → no sync; configured with bad URL → action still succeeds, sync may fail | Ensures the Ash change and after_transaction arity are correct and the action result is not broken by sync failures. |
+
+## What is *not* tested (and would need a stub or real endpoint)
+
+- Actual HTTP request shape (body, headers) and response handling (201/200, error codes).  
+- Persistence of `vereinfacht_contact_id` after a successful create.  
+- Translation of specific API error payloads into user messages.
+
+Those would require either a **Bypass** (or similar) stub in front of Req or a dedicated test endpoint; both are out of scope for the current “no real API” setup.
+
+## Conclusion
+
+Given the constraint that the API is not called in CI, the tests are **meaningful**: they cover config, “not configured” paths, and integration of SyncContact with Member create/update without crashing. They are **sufficient** for regression safety and refactoring; extending them with a Bypass stub would be an optional next step if we want to assert on request/response shape without hitting the real API.