diff --git a/test/fixtures/colors.yml b/test/fixtures/colors.yml
new file mode 100644
index 00000000..b31ffcc9
--- /dev/null
+++ b/test/fixtures/colors.yml
@@ -0,0 +1,3 @@
+purple:
+  id: 57
+  name: purple
diff --git a/test/fixtures/species.yml b/test/fixtures/species.yml
new file mode 100644
index 00000000..04ce807b
--- /dev/null
+++ b/test/fixtures/species.yml
@@ -0,0 +1,3 @@
+chia:
+  id: 7
+  name: chia
diff --git a/test/mocks/custom_pets/thyassa.json b/test/mocks/custom_pets/thyassa.json
new file mode 100644
index 00000000..5da69647
--- /dev/null
+++ b/test/mocks/custom_pets/thyassa.json
@@ -0,0 +1,60 @@
+{
+  "custom_pet": {
+    "name": "thyassa",
+    "owner": "donna",
+    "slot": 1.0,
+    "scale": 0.5,
+    "muted": false,
+    "body_id": 212.0,
+    "species_id": 7.0,
+    "color_id": 57.0,
+    "alt_style": false,
+    "alt_color": 57.0,
+    "style_closet_id": null,
+    "biology_by_zone": {
+      "37": {
+        "part_id": 10083.0,
+        "zone_id": 37.0,
+        "asset_url": "https://images.neopets.com/cp/bio/swf/000/000/010/10083_8a1111a13f.swf",
+        "manifest": "https://images.neopets.com/cp/bio/data/000/000/010/10083_8a1111a13f/manifest.json",
+        "zones_restrict": "0000000000000000000000000000000000000000000000000000"
+      },
+      "15": {
+        "part_id": 11613.0,
+        "zone_id": 15.0,
+        "asset_url": "https://images.neopets.com/cp/bio/swf/000/000/011/11613_f7d8d377ab.swf",
+        "manifest": "https://images.neopets.com/cp/bio/data/000/000/011/11613_f7d8d377ab/manifest.json",
+        "zones_restrict": "0000000000000000000000000000000000000000000000000000"
+      },
+      "34": {
+        "part_id": 14187.0,
+        "zone_id": 34.0,
+        "asset_url": "https://images.neopets.com/cp/bio/swf/000/000/014/14187_0e65c2082f.swf",
+        "manifest": "https://images.neopets.com/cp/bio/data/000/000/014/14187_0e65c2082f/manifest.json",
+        "zones_restrict": "0000000000000000000000000000000000000000000000000000"
+      },
+      "33": {
+        "part_id": 14189.0,
+        "zone_id": 33.0,
+        "asset_url": "https://images.neopets.com/cp/bio/swf/000/000/014/14189_102e4991e9.swf",
+        "manifest": "https://images.neopets.com/cp/bio/data/000/000/014/14189_102e4991e9/manifest.json",
+        "zones_restrict": "0000000000000000000000000000000000000000000000000000"
+      }
+    },
+    "equipped_by_zone": [
+
+    ],
+    "original_biology": [
+
+    ]
+  },
+  "closet_items": [
+
+  ],
+  "object_info_registry": [
+
+  ],
+  "object_asset_registry": [
+
+  ]
+}
diff --git a/test/modeling.rb b/test/modeling.rb
new file mode 100644
index 00000000..eee540dc
--- /dev/null
+++ b/test/modeling.rb
@@ -0,0 +1,16 @@
+require 'test_helper'
+
+class ModelingTest < ActiveSupport::TestCase
+	test "Modeling thyassa gives us Purple Chia data" do
+		thyassa = Pet.load("thyassa")
+
+		# The Purple Chia starts as a new record, hooked up to the existing
+		# Purple color and Chia species.
+		purple_chia = thyassa.pet_type
+		assert purple_chia.new_record?
+		assert_equal Color.find_by_name("purple"), purple_chia.color
+		assert_equal Species.find_by_name("chia"), purple_chia.species
+		assert_equal 212, purple_chia.body_id
+		assert_equal "mock-image-hash:thyassa", purple_chia.image_hash
+	end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 8bf1192f..354abff3 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -11,3 +11,20 @@ class ActiveSupport::TestCase
 
   # Add more helper methods to be used by all tests here...
 end
+
+# We replace Neopets::CustomPets methods with a mocked implementation.
+module Neopets::CustomPets
+  def self.fetch_viewer_data(pet_name, ...)
+    File.open(Rails.root / "test/mocks/custom_pets/#{pet_name}.json") do |file|
+      HashWithIndifferentAccess.new JSON.load(file)
+    end
+  end
+
+  def self.fetch_metadata(...)
+    raise NotImplementedError
+  end
+
+  def self.fetch_image_hash(pet_name, ...)
+    "mock-image-hash:#{pet_name}"
+  end
+end