test(products): INV-12 property test — export round-trips to a no-op (SD-0002 §6.8)

backend/tests/test_products_serialize.py

@@ -102,3 +102,71 @@ def test_more_images_than_variants_emits_image_only_rows():
     assert rows[0]["Variant SKU"] == "WG-MUG"
     assert rows[1]["Variant SKU"] == "" and rows[1]["Handle"] == "moon-mug"
     assert [r["Image Src"] for r in rows] == ["https://x/a.jpg", "https://x/b.jpg", "https://x/c.jpg"]
+
+
+import random
+
+from app.domains.products import codec, diff, validate
+
+
+def _gen_catalog(seed: int) -> dict:
+    """A deterministic random text-field catalog, in load_catalog()'s shape."""
+    rng = random.Random(seed)
+    words = ["moon", "star", "river", "cloud", "ember", "fern", "slate", "wave"]
+    catalog: dict[str, CatalogProduct] = {}
+    n_products = rng.randint(1, 6)
+    for pid in range(1, n_products + 1):
+        handle = "-".join(rng.sample(words, rng.randint(1, 3))) + f"-{pid}"
+        if handle in catalog:
+            continue
+        has_opts = rng.random() < 0.6
+        option_names = ("Size", "Color", None) if has_opts else (None, None, None)
+        tags = rng.sample(["apparel", "kitchen", "sale", "new"], rng.randint(0, 3))
+        fields = {
+            "title": f"{handle.title()} Thing",
+            "description_html": rng.choice([None, "<p>hi</p>"]),
+            "vendor": rng.choice([None, "Acme", "Wiggle Goods"]),
+            "product_type": "standalone",
+            "google_product_category": rng.choice([None, "Home & Garden"]),
+            "tags": tags,
+            "status": rng.choice(["draft", "active", "archived"]),
+            "published": rng.choice([True, False]),
+        }
+        variants = []
+        if has_opts:
+            sizes = rng.sample(["S", "M", "L", "XL"], rng.randint(1, 4))
+            for vi, size in enumerate(sizes, start=1):
+                variants.append(CatalogVariant(
+                    id=pid * 100 + vi, options=(size, "Indigo", None), position=vi,
+                    fields={"sku": f"SKU-{pid}-{vi}", "variant_image": None}))
+        else:
+            variants.append(CatalogVariant(
+                id=pid * 100 + 1, options=(None, None, None), position=1,
+                fields={"sku": f"SKU-{pid}", "variant_image": None}))
+        images = []
+        for ii in range(rng.randint(0, 3)):
+            images.append(CatalogImage(
+                id=pid * 10 + ii, source_url=f"https://img/{handle}-{ii}.jpg",
+                position=ii + 1, alt_text=rng.choice([None, f"alt {ii}"])))
+        catalog[handle] = CatalogProduct(
+            id=pid, handle=handle, title=fields["title"], option_names=option_names,
+            fields=fields, variants=variants, images=images)
+    return catalog
+
+
+def _roundtrip_diff(catalog: dict) -> diff.DiffResult:
+    """export → bytes → import pipeline → diff against the same catalog."""
+    text = "".join(serialize.catalog_to_csv(catalog.values()))
+    parsed = codec.parse_csv(text.encode("utf-8"))
+    products = validate.build_products(parsed)
+    return diff.compute_diff(catalog, products)
+
+
+def test_inv12_roundtrip_is_noop_over_generated_catalogs():
+    for seed in range(200):
+        catalog = _gen_catalog(seed)
+        result = _roundtrip_diff(catalog)
+        assert result.summary["adds"] == 0, f"seed {seed}: {result.summary}"
+        assert result.summary["updates"] == 0, f"seed {seed}: {result.summary}"
+        assert result.summary["errors"] == 0, f"seed {seed}: {result.summary}"
+        assert result.summary["unchanged"] == len(catalog), f"seed {seed}"