diff --git a/test/mv_web/member_live/show_groups_display_test.exs b/test/mv_web/member_live/show_groups_display_test.exs
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+++ b/test/mv_web/member_live/show_groups_display_test.exs
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+defmodule MvWeb.MemberLive.ShowGroupsDisplayTest do
+  @moduledoc """
+  Tests for displaying groups in the member detail view (Issue #374).
+
+  Tests cover:
+  - Groups section visibility (with and without groups)
+  - Group badges with correct names and links to group detail pages
+  - Edge cases (one group, many groups)
+  - Security: groups section visible only when user may view member
+  - Accessibility: badges have role and aria-label
+
+  ## Note on async
+  async: false to avoid PostgreSQL deadlocks when creating members and groups
+  in the same test run (same as IndexGroupsDisplayTest).
+
+  ## Expected state
+  These tests fail until the Groups section is implemented on the member show page
+  (Issue #374: load groups in handle_params, add "Groups" section with badges and links).
+  """
+  use MvWeb.ConnCase, async: false
+  import Phoenix.LiveViewTest
+  require Ash.Query
+  use Gettext, backend: MvWeb.Gettext
+
+  alias Mv.Membership.{Group, MemberGroup}
+
+  describe "groups section" do
+    setup do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Alice", last_name: "Anderson", email: "alice@example.com"},
+          actor: system_actor
+        )
+
+      %{member: member, actor: system_actor}
+    end
+
+    test "displays Groups section when member has at least one group", %{
+      conn: conn,
+      member: member,
+      actor: actor
+    } do
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      conn = conn_with_oidc_user(conn)
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ gettext("Groups")
+      assert html =~ group.name
+    end
+
+    test "displays all groups as badges with correct names when member is in multiple groups", %{
+      conn: conn,
+      member: member,
+      actor: actor
+    } do
+      {:ok, group1} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+        |> Ash.create(actor: actor)
+
+      {:ok, group2} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Active Members"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg1} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group1.id})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg2} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group2.id})
+        |> Ash.create(actor: actor)
+
+      conn = conn_with_oidc_user(conn)
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ gettext("Groups")
+      assert html =~ group1.name
+      assert html =~ group2.name
+    end
+
+    test "displays Groups section when member has no groups (empty state)", %{
+      conn: conn,
+      member: member
+    } do
+      conn = conn_with_oidc_user(conn)
+      {:ok, view, _html} = live(conn, ~p"/members/#{member}")
+
+      # Assert Groups section in main content (section with h2 "Groups"), not sidebar link
+      assert has_element?(view, "main section h2", gettext("Groups"))
+    end
+
+    test "groups are loaded with member (single request returns all group names)", %{
+      conn: conn,
+      member: member,
+      actor: actor
+    } do
+      {:ok, group1} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Alpha"})
+        |> Ash.create(actor: actor)
+
+      {:ok, group2} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Beta"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg1} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group1.id})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg2} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group2.id})
+        |> Ash.create(actor: actor)
+
+      conn = conn_with_oidc_user(conn)
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ "Alpha"
+      assert html =~ "Beta"
+    end
+  end
+
+  describe "groups section links" do
+    setup do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Bob", last_name: "Brown", email: "bob@example.com"},
+          actor: system_actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Board Members"})
+        |> Ash.create(actor: system_actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: system_actor)
+
+      %{member: member, group: group}
+    end
+
+    test "each group badge links to group detail page with correct slug", %{
+      conn: conn,
+      member: member,
+      group: group
+    } do
+      conn = conn_with_oidc_user(conn)
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      # Link to group detail: /groups/:slug (slug is URL-friendly, e.g. "board-members")
+      assert html =~ ~r/href="[^"]*\/groups\/#{Regex.escape(group.slug)}"|navigate="[^"]*\/groups\/#{Regex.escape(group.slug)}"/
+    end
+
+    test "clicking group badge navigates to group detail page", %{
+      conn: conn,
+      member: member,
+      group: group
+    } do
+      conn = conn_with_oidc_user(conn)
+      {:ok, view, _html} = live(conn, ~p"/members/#{member}")
+
+      view
+      |> element("a[href*='/groups/#{group.slug}']")
+      |> render_click()
+
+      assert_redirect(view, ~p"/groups/#{group.slug}")
+    end
+  end
+
+  describe "groups section edge cases" do
+    setup do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Charlie", last_name: "Clark", email: "charlie@example.com"},
+          actor: system_actor
+        )
+
+      %{member: member, actor: system_actor}
+    end
+
+    test "member in exactly one group shows single badge", %{
+      conn: conn,
+      member: member,
+      actor: actor
+    } do
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Solo Group"})
+        |> Ash.create(actor: actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: actor)
+
+      conn = conn_with_oidc_user(conn)
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ gettext("Groups")
+      assert html =~ group.name
+    end
+
+    test "member in many groups shows all badges", %{
+      conn: conn,
+      member: member,
+      actor: actor
+    } do
+      group_names = Enum.map(1..5, fn i -> "Group #{i}" end)
+
+      groups =
+        Enum.map(group_names, fn name ->
+          {:ok, g} =
+            Group
+            |> Ash.Changeset.for_create(:create, %{name: name})
+            |> Ash.create(actor: actor)
+
+          g
+        end)
+
+      for g <- groups do
+        {:ok, _mg} =
+          MemberGroup
+          |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: g.id})
+          |> Ash.create(actor: actor)
+      end
+
+      conn = conn_with_oidc_user(conn)
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ gettext("Groups")
+      for name <- group_names do
+        assert html =~ name
+      end
+    end
+  end
+
+  describe "groups section with read_only user" do
+    @tag role: :read_only
+    test "user with read permission sees Groups section", %{conn: conn} do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Diana", last_name: "Davis", email: "diana@example.com"},
+          actor: system_actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "Readers"})
+        |> Ash.create(actor: system_actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: system_actor)
+
+      {:ok, _view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ gettext("Groups")
+      assert html =~ group.name
+    end
+  end
+
+  describe "groups section accessibility" do
+    setup do
+      system_actor = Mv.Helpers.SystemActor.get_system_actor()
+
+      {:ok, member} =
+        Mv.Membership.create_member(
+          %{first_name: "Eve", last_name: "Evans", email: "eve@example.com"},
+          actor: system_actor
+        )
+
+      {:ok, group} =
+        Group
+        |> Ash.Changeset.for_create(:create, %{name: "A11y Group"})
+        |> Ash.create(actor: system_actor)
+
+      {:ok, _mg} =
+        MemberGroup
+        |> Ash.Changeset.for_create(:create, %{member_id: member.id, group_id: group.id})
+        |> Ash.create(actor: system_actor)
+
+      %{member: member, group: group}
+    end
+
+    test "group badges have role and aria-label for screen readers", %{
+      conn: conn,
+      member: member,
+      group: group
+    } do
+      conn = conn_with_oidc_user(conn)
+      {:ok, view, html} = live(conn, ~p"/members/#{member}")
+
+      assert html =~ group.name
+      # Badge has role="status" and aria-label indicating group membership (architecture: "Member of group X")
+      assert has_element?(view, "[role='status'][aria-label*='#{group.name}']")
+    end
+  end
+end