diff --git a/lib/admin/accounts/account.ex b/lib/admin/accounts/account.ex
index 42458f718..c46a7d72f 100644
--- a/lib/admin/accounts/account.ex
+++ b/lib/admin/accounts/account.ex
@@ -21,7 +21,7 @@ defmodule Admin.Accounts.Account do
     |> cast(attrs, [:name, :email, :type, :extra])
     |> validate_required([:name, :email, :type])
     |> validate_email()
-    |> maybe_validate_lang(:extra)
+    |> validate_change(:extra, fn _, value -> validate_lang(value) end)
   end
 
   defp validate_email(changeset) do
@@ -33,37 +33,18 @@ defmodule Admin.Accounts.Account do
   end
 
   # Validates `lang` only if present; permits nil or empty maps.
-  defp maybe_validate_lang(changeset, field) when is_atom(field) do
-    map = get_field(changeset, field)
+  defp validate_lang(map) when is_map(map) and map == %{}, do: []
 
-    cond do
-      # Skip validation if nil or empty map
-      is_nil(map) or (is_map(map) and map == %{}) ->
-        changeset
+  defp validate_lang(map) when is_map(map) do
+    case Map.fetch(map, "lang") do
+      :error ->
+        []
 
-      # If provided but not a map, type error
-      not is_map(map) ->
-        add_error(changeset, field, "must be a map")
+      {:ok, lang} when is_binary(lang) and lang != "" ->
+        []
 
-      true ->
-        map_contains_string(changeset, field, map, :lang)
-    end
-  end
-
-  defp map_contains_string(changeset, field, map, key) do
-    case Map.get(map, key) do
-      nil ->
-        # Key absent is OK
-        changeset
-
-      v when is_binary(v) and v != "" ->
-        changeset
-
-      v when is_binary(v) ->
-        add_error(changeset, field, "\"lang\" must be a non-empty string")
-
-      _ ->
-        add_error(changeset, field, "\"lang\" must be a string")
+      {:ok, _} ->
+        [extra: {"must be a non-empty string", []}]
     end
   end
 end
diff --git a/test/admin/blog_test.exs b/test/admin/blog_test.exs
new file mode 100644
index 000000000..5910fcfc3
--- /dev/null
+++ b/test/admin/blog_test.exs
@@ -0,0 +1,139 @@
+defmodule Admin.BlogTest do
+  use ExUnit.Case, async: true
+
+  alias Admin.Blog
+  alias Admin.Blog.Parser
+  alias Admin.Blog.Post
+
+  describe "blog parser" do
+    test "parses yaml frontmatter" do
+      content = """
+      ---
+      title: hello
+      other:
+        - hey
+        - you
+      ---
+
+      This is the blog content
+      """
+
+      assert {%{"other" => ["hey", "you"], "title" => "hello"}, "\nThis is the blog content\n"} =
+               Parser.parse("somepath", content)
+    end
+
+    test "raises if missing the delimiter" do
+      content = """
+      title: hello
+      other:
+        - hey
+        - you
+
+      This is the blog content
+      """
+
+      assert_raise MatchError, fn ->
+        Parser.parse("somepath", content)
+      end
+    end
+
+    test "raises if not yaml frontmatter the delimiter" do
+      content = """
+      %{
+        title: "hello"
+        other: ["hey", "you"]
+      }
+      ---
+
+      This is the blog content
+      """
+
+      assert_raise MatchError, fn ->
+        Parser.parse("somepath", content)
+      end
+    end
+
+    test "no content is ok" do
+      content = """
+      title: hello
+      other:
+        - hey
+        - you
+      ---
+      """
+
+      assert {%{"other" => ["hey", "you"], "title" => "hello"}, ""} =
+               Parser.parse("somepath", content)
+    end
+  end
+
+  describe "blog posts" do
+    test "can get all posts" do
+      assert Blog.all_posts()
+    end
+
+    test "can get a post by id" do
+      assert Blog.get_post_by_id!("2026-01-19-production-release")
+    end
+
+    test "post that does not exist raises" do
+      assert_raise AdminWeb.NotFoundError, fn ->
+        Blog.get_post_by_id!("nonexistent-post-id")
+      end
+    end
+
+    test "posts by year" do
+      assert posts = Blog.posts_by_year()
+      assert posts |> Enum.find(fn {year, posts_for_year} -> year == 2026 end)
+    end
+  end
+
+  describe "blog post" do
+    test "can build a blog post struct" do
+      assert %Post{
+               id: "2026-01-01-my-post-id",
+               title: "hello",
+               date: ~D[2026-01-01],
+               tags: [],
+               authors: ["hey", "you"],
+               body: "Content"
+             } =
+               Post.build(
+                 "2026/01-01-my-post-id",
+                 %{
+                   "title" => "hello",
+                   "authors" => ["hey", "you"]
+                 },
+                 "Content"
+               )
+    end
+
+    test "parses the description from the content" do
+      content = """
+      This is the description of the post.
+
+      <!-- truncate -->
+
+      This is the rest of the post.
+      """
+
+      assert %Post{
+               id: "2026-01-01-my-post-id",
+               title: "hello",
+               date: ~D[2026-01-01],
+               tags: [],
+               description: "This is the description of the post.\n\n",
+               authors: ["hey", "you"],
+               body: ^content
+             } =
+               Post.build(
+                 "2026/01-01-my-post-id",
+                 %{
+                   "title" => "hello",
+                   "authors" => ["hey", "you"]
+                 },
+                 content
+               )
+    end
+  end
+end
diff --git a/test/admin/members_test.exs b/test/admin/members_test.exs
new file mode 100644
index 000000000..0b0a1da91
--- /dev/null
+++ b/test/admin/members_test.exs
@@ -0,0 +1,66 @@
+defmodule Admin.MembersTest do
+  use Admin.DataCase
+
+  alias Admin.Accounts
+
+  describe "member extra" do
+    test "no extra is ok" do
+      assert {:ok, member} =
+               Accounts.create_member(%{
+                 name: "Someone",
+                 email: "unknown@example.com",
+                 type: "individual"
+               })
+
+      assert member.extra == nil
+    end
+
+    test "no lang in extra is ok" do
+      assert {:ok, member} =
+               Accounts.create_member(%{
+                 name: "Someone",
+                 email: "unknown@example.com",
+                 type: "individual",
+                 extra: %{}
+               })
+
+      assert member.extra == %{}
+    end
+
+    test "fails if extra is not a map" do
+      assert {:error, %Ecto.Changeset{} = changeset} =
+               Accounts.create_member(%{
+                 name: "Someone",
+                 email: "unknown@example.com",
+                 type: "individual",
+                 extra: ["not a map"]
+               })
+
+      assert changeset.errors[:extra] == {"is invalid", [{:type, :map}, {:validation, :cast}]}
+    end
+
+    test "fails if lang in extra is empty" do
+      assert {:error, %Ecto.Changeset{} = changeset} =
+               Accounts.create_member(%{
+                 name: "Someone",
+                 email: "unknown@example.com",
+                 type: "individual",
+                 extra: %{"lang" => ""}
+               })
+
+      assert changeset.errors[:extra] == {"must be a non-empty string", []}
+    end
+
+    test "has a valid lang in extra" do
+      assert {:ok, member} =
+               Accounts.create_member(%{
+                 name: "Someone",
+                 email: "unknown@example.com",
+                 type: "individual",
+                 extra: %{"lang" => "en"}
+               })
+
+      assert member.extra == %{"lang" => "en"}
+    end
+  end
+end
diff --git a/test/admin/static_pages_test.exs b/test/admin/static_pages_test.exs
new file mode 100644
index 000000000..9d5cc0fe4
--- /dev/null
+++ b/test/admin/static_pages_test.exs
@@ -0,0 +1,45 @@
+defmodule Admin.StaticPagesTest do
+  use ExUnit.Case, async: true
+
+  alias Admin.StaticPages
+  alias Admin.StaticPages.Page
+
+  describe "static pages" do
+    test "can get required pages" do
+      assert ["disclaimer", "privacy", "terms"] = StaticPages.get_unique_page_ids()
+    end
+
+    test "get pages in en" do
+      assert StaticPages.get_static_page!("en", "disclaimer")
+      assert StaticPages.get_static_page!("en", "terms")
+      assert StaticPages.get_static_page!("en", "privacy")
+
+      assert_raise AdminWeb.NotFoundError, fn ->
+        StaticPages.get_static_page!("en", "nonexistent")
+      end
+    end
+
+    test "page exists" do
+      assert StaticPages.exists?("en", "disclaimer")
+      refute StaticPages.exists?("en", "nonexistent")
+    end
+  end
+
+  describe "page struct" do
+    test "can build a page from a file" do
+      assert %Page{
+               id: "disclaimer",
+               locale: "en",
+               title: "Disclaimer",
+               body: "Content"
+             } =
+               Page.build(
+                 "en/disclaimer.md",
+                 %{
+                   title: "Disclaimer"
+                 },
+                 "Content"
+               )
+    end
+  end
+end