Stricter validations for ToolSLot (avoid double slotting at DB layer, too)

db/migrate/20190419001321_stricter_validation_for_tool_id.rb

@@ -0,0 +1,7 @@
+class StricterValidationForToolId < ActiveRecord::Migration[5.2]
+  def change
+    safety_assured do
+      add_index :points, [:device_id, :tool_id], unique: true
+    end
+  end
+end

db/structure.sql

@@ -2405,6 +2405,13 @@ CREATE INDEX index_plant_templates_on_saved_garden_id ON public.plant_templates
 CREATE INDEX index_points_on_device_id ON public.points USING btree (device_id);
 
 
+--
+-- Name: index_points_on_device_id_and_tool_id; Type: INDEX; Schema: public; Owner: -
+--
+
+CREATE UNIQUE INDEX index_points_on_device_id_and_tool_id ON public.points USING btree (device_id, tool_id);
+
+
 --
 -- Name: index_points_on_discarded_at; Type: INDEX; Schema: public; Owner: -
 --
@@ -2895,6 +2902,7 @@ INSERT INTO "schema_migrations" (version) VALUES
 ('20190411171401'),
 ('20190411222900'),
 ('20190416035406'),
-('20190417165636');
+('20190417165636'),
+('20190419001321');
 
 

spec/models/point_spec.rb

@@ -1,2 +0,0 @@
-describe Point do
-end

spec/models/tool_slot_spec.rb

@@ -0,0 +1,10 @@
+describe ToolSlot do
+  it "does not allow double slotting of tools" do
+    slot1  = FactoryBot.create(:tool_slot)
+    device = slot1.device
+    tool   = slot1.tool
+    expect do
+      FactoryBot.create(:tool_slot, device: device, tool: tool)
+    end.to raise_error(ActiveRecord::RecordInvalid)
+  end
+end