spec(orm): test serializable instance without table

spec/adapter_tests/orm/migrations/migrations.cr

@@ -74,3 +74,32 @@ class Tag < DBX::ORM::Model
     relation profiles : Array(Profile)
   end
 end
+
+# Just a noop Model without relation nor table.
+class Noop < DBX::ORM::Model
+  # For generic tests adapters
+  {% if ADAPTER_NAME == :pg %}adapter :pg{% end %}
+  {% if ADAPTER_NAME == :sqlite %}adapter :sqlite{% end %}
+
+  table :noop
+  connection "app"
+
+  class_getter pk_name : String = "uid"
+  class_getter pk_type = String
+  class_getter fk_name = "noop_uid"
+
+  # DB table schema
+  class Schema < DBX::ORM::Schema
+    @[DB::Field(ignore: true)]
+    @[JSON::Field(ignore: true)]
+    def _pk
+      self.uid
+    end
+
+    @[JSON::Field(key: "createdAt")]
+    field created_at : Time
+
+    field uid : String
+    field name : String
+  end
+end

spec/adapter_tests/orm/model/schema_tests.cr

@@ -126,6 +126,24 @@ describe DBX::ORM::Schema do
     )
   end
 
+  it "should be able to create a serializable instance even if there is no table" do
+    now = Time.utc
+    noop = Noop::Schema.new(created_at: now, name: "noop", uid: "uuuuuu")
+    noop.should be_a DBX::ORM::Schema
+    noop.created_at.should be_a Time
+    noop.created_at.should eq now
+    noop.uid.should eq "uuuuuu"
+    noop.name.should eq "noop"
+    noop.to_json.should eq %({"createdAt":"#{now.to_rfc3339}","uid":"uuuuuu","name":"noop"})
+
+    noop = Noop::Schema.from_json %({"createdAt":"#{now.to_rfc3339(fraction_digits: 9)}","uid":"iii","name":"noop2"})
+    noop.should be_a DBX::ORM::Schema
+    noop.created_at.should be_a Time
+    noop.created_at.should eq now
+    noop.uid.should eq "iii"
+    noop.name.should eq "noop2"
+  end
+
   pending ".from_rs" do
     User
   end