diff --git a/test/accounts/user_member_relationship_test.exs b/test/accounts/user_member_relationship_test.exs
new file mode 100644
index 0000000..19cbe62
--- /dev/null
+++ b/test/accounts/user_member_relationship_test.exs
@@ -0,0 +1,195 @@
+defmodule Mv.Accounts.UserMemberRelationshipTest do
+  use Mv.DataCase, async: false
+  alias Mv.Accounts
+  alias Mv.Membership
+
+  describe "User-Member Relationship - Basic Tests" do
+    @valid_user_attrs %{
+      email: "test@example.com"
+    }
+
+    @valid_member_attrs %{
+      first_name: "John",
+      last_name: "Doe",
+      email: "john@example.com"
+    }
+
+    test "user can exist without member" do
+      {:ok, user} = Accounts.create_user(@valid_user_attrs)
+      assert user.member_id == nil
+
+      # Load the relationship to test it
+      {:ok, user_with_member} = Ash.get(Mv.Accounts.User, user.id, load: [:member])
+      assert user_with_member.member == nil
+    end
+
+    test "member can exist without user" do
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+      assert member.id != nil
+      assert member.first_name == "John"
+
+      # Load the relationship to test it
+      {:ok, member_with_user} = Ash.get(Mv.Membership.Member, member.id, load: [:user])
+      assert member_with_user.user == nil
+    end
+  end
+
+  describe "User-Member Relationship - Linking Tests" do
+    @valid_user_attrs %{
+      email: "test1@example.com"
+    }
+
+    @valid_member_attrs %{
+      first_name: "Alice",
+      last_name: "Johnson",
+      email: "alice@example.com"
+    }
+
+    test "user can be linked to member during user creation" do
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      user_attrs = Map.put(@valid_user_attrs, :member, %{id: member.id})
+      {:ok, user} = Accounts.create_user(user_attrs)
+
+      # Load the relationship to test it
+      {:ok, user_with_member} = Ash.get(Mv.Accounts.User, user.id, load: [:member])
+      assert user_with_member.member.id == member.id
+    end
+
+    test "member can be linked to user during member creation using manage_relationship" do
+      {:ok, user} = Accounts.create_user(@valid_user_attrs)
+
+      member_attrs = Map.put(@valid_member_attrs, :user, %{id: user.id})
+      {:ok, member} = Membership.create_member(member_attrs)
+
+      # Load the relationship to test it
+      {:ok, member_with_user} = Ash.get(Mv.Membership.Member, member.id, load: [:user])
+      assert member_with_user.user.id == user.id
+    end
+
+    test "user can be linked to member during update" do
+      {:ok, user} = Accounts.create_user(@valid_user_attrs)
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      {:ok, updated_user} = Accounts.update_user(user, %{member: %{id: member.id}})
+
+      # Load the relationship to test it
+      {:ok, user_with_member} = Ash.get(Mv.Accounts.User, updated_user.id, load: [:member])
+      assert user_with_member.member.id == member.id
+    end
+
+    test "member can be linked to user during update using manage_relationship" do
+      {:ok, user} = Accounts.create_user(@valid_user_attrs)
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      {:ok, _updated_member} = Membership.update_member(member, %{user: %{id: user.id}})
+
+      # Load the relationship to test it
+      {:ok, member_with_user} = Ash.get(Mv.Membership.Member, member.id, load: [:user])
+      assert member_with_user.user.id == user.id
+    end
+  end
+
+  describe "User-Member Relationship - Inverse Relationship Tests" do
+    @valid_user_attrs %{
+      email: "test2@example.com"
+    }
+
+    @valid_member_attrs %{
+      first_name: "Bob",
+      last_name: "Smith",
+      email: "bob@example.com"
+    }
+
+    test "ash resolves inverse relationship automatically" do
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      user_attrs = Map.put(@valid_user_attrs, :member, %{id: member.id})
+      {:ok, user} = Accounts.create_user(user_attrs)
+
+      # Load relationships
+      {:ok, user_with_member} = Ash.get(Mv.Accounts.User, user.id, load: [:member])
+      {:ok, member_with_user} = Ash.get(Mv.Membership.Member, member.id, load: [:user])
+
+      assert user_with_member.member.id == member.id
+      assert member_with_user.user.id == user.id
+    end
+
+    test "member can find associated user" do
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      {:ok, user} = Accounts.create_user(%{email: "test3@example.com", member: %{id: member.id}})
+      {:ok, member_with_user} = Ash.get(Mv.Membership.Member, member.id, load: [:user])
+      assert member_with_user.user.id == user.id
+    end
+  end
+
+  describe "User-Member Relationship - Preventing Duplicates" do
+    @valid_user_attrs %{
+      email: "test4@example.com"
+    }
+
+    @valid_member_attrs %{
+      first_name: "Charlie",
+      last_name: "Brown",
+      email: "charlie@example.com"
+    }
+
+    test "prevents overwriting a member of already linked user on update" do
+      {:ok, existing_member} = Membership.create_member(@valid_member_attrs)
+
+      user_attrs = Map.put(@valid_user_attrs, :member, %{id: existing_member.id})
+      {:ok, user} = Accounts.create_user(user_attrs)
+
+      {:ok, member2} =
+        Membership.create_member(%{
+          first_name: "Dave",
+          last_name: "Wilson",
+          email: "dave@example.com"
+        })
+
+      assert {:error, %Ash.Error.Invalid{}} =
+               Accounts.update_user(user, %{member: %{id: member2.id}})
+    end
+
+    test "prevents linking user to already linked member on update" do
+      {:ok, existing_user} = Accounts.create_user(@valid_user_attrs)
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      {:ok, _updated_user} = Accounts.update_user(existing_user, %{member: %{id: member.id}})
+
+      {:ok, user2} = Accounts.create_user(%{email: "test5@example.com"})
+
+      assert {:error, %Ash.Error.Invalid{}} =
+               Accounts.update_user(user2, %{member: %{id: member.id}})
+    end
+
+    test "prevents linking member to already linked user on creation" do
+      {:ok, existing_member} = Membership.create_member(@valid_member_attrs)
+
+      user_attrs = Map.put(@valid_user_attrs, :member, %{id: existing_member.id})
+      {:ok, user} = Accounts.create_user(user_attrs)
+
+      assert {:error, %Ash.Error.Invalid{}} =
+               Membership.create_member(%{
+                 first_name: "Dave",
+                 last_name: "Wilson",
+                 email: "dave@example.com",
+                 user: %{id: user.id}
+               })
+    end
+
+    test "prevents linking user to already linked member on creation" do
+      {:ok, existing_user} = Accounts.create_user(@valid_user_attrs)
+      {:ok, member} = Membership.create_member(@valid_member_attrs)
+
+      {:ok, _updated_user} = Accounts.update_user(existing_user, %{member: %{id: member.id}})
+
+      assert {:error, %Ash.Error.Invalid{}} =
+               Accounts.create_user(%{
+                 email: "test5@example.com",
+                 member: %{id: member.id}
+               })
+    end
+  end
+end