Add the validation for Book's page count to be greater than 0.

lib/decentralised_book_index/metadata/book.ex

@@ -302,6 +302,10 @@ defmodule DecentralisedBookIndex.Metadata.Book do
     end
   end
 
+  validations do
+    validate numericality(:page_count, greater_than: 0)
+  end
+
   relationships do
     belongs_to :dbi_server, Metadata.DBIServer
 

test/decentralised_book_index/metadata/forms/book_form_test.exs

@@ -1,7 +1,10 @@
 defmodule DecentralisedBookIndex.Metadata.Forms.BookFormTest do
   use DecentralisedBookIndex.DataCase, async: true
 
+  import ExUnitProperties
+
   alias DecentralisedBookIndex.Metadata
+  alias DecentralisedBookIndex.Metadata.Book
 
   describe "create new book via the form" do
     test "just name and description" do
@@ -69,4 +72,52 @@ defmodule DecentralisedBookIndex.Metadata.Forms.BookFormTest do
       assert {:ok, user} = AshPhoenix.Form.submit(form, params: valid_params)
     end
   end
+
+  describe "validation" do
+    property "the book form is valid if the page count > 0" do
+      user = generate(user())
+      book = generate(book())
+
+      valid_count_generator =
+        StreamData.integer()
+        |> StreamData.map(fn n -> abs(n)+1 end)
+
+      check all(page_count <- valid_count_generator) do
+        valid_params = %{
+          "page_count" => page_count,
+        }
+
+        form =
+          AshPhoenix.Form.for_update(book, :update,
+            as: "book",
+            actor: user
+          )
+
+        assert {:ok, _book} = AshPhoenix.Form.submit(form, params: valid_params)
+      end
+    end
+
+    property "the book form is invalid if the page count <= 0" do
+      user = generate(user())
+      book = generate(book())
+
+      invalid_count_generator =
+        StreamData.integer()
+        |> StreamData.map(fn n -> -abs(n) end)
+
+      check all(page_count <- invalid_count_generator) do
+        invalid_params = %{
+          "page_count" => page_count,
+        }
+
+        form =
+          AshPhoenix.Form.for_update(book, :update,
+            as: "book",
+            actor: user
+          )
+
+        assert {:error, _error} = AshPhoenix.Form.submit(form, params: invalid_params)
+      end
+    end
+  end
 end

test/support/generators.ex

@@ -189,7 +189,7 @@ defmodule DecentralisedBookIndex.Generators do
         description: sequence(:description, &"Description #{&1}"),
         language: sequence(:language, &"Language #{&1}"),
         format: sequence(:format, &"Format #{&1}"),
-        page_count: sequence(:page_count, & &1),
+        page_count: sequence(:page_count, &(abs(&1)+1)),
         published: sequence(:published, &Date.add(~D[2025-03-04], &1)),
         bids: bids,
         author_roles: author_roles,