feat(random): multi-theme groundwork, locked reroll export parity, duplicate export fix, expanded diagnostics and test coverage

code/tests/test_random_reroll_idempotency.py

@@ -0,0 +1,43 @@
+import os
+
+import pytest
+from fastapi.testclient import TestClient
+
+
+@pytest.fixture(scope="module")
+def client():
+    # Ensure flags and frozen dataset
+    os.environ["RANDOM_MODES"] = "1"
+    os.environ["RANDOM_UI"] = "1"
+    os.environ["CSV_FILES_DIR"] = os.path.join("csv_files", "testdata")
+
+    from web.app import app
+
+    with TestClient(app) as c:
+        yield c
+
+
+def test_reroll_idempotency_and_progression(client: TestClient):
+    # Initial build
+    base_seed = 2024
+    r1 = client.post("/api/random_full_build", json={"seed": base_seed})
+    assert r1.status_code == 200, r1.text
+    d1 = r1.json()
+    deck1 = d1.get("decklist")
+    assert isinstance(deck1, list) and deck1
+
+    # Rebuild with the same seed should produce identical result
+    r_same = client.post("/api/random_full_build", json={"seed": base_seed})
+    assert r_same.status_code == 200, r_same.text
+    deck_same = r_same.json().get("decklist")
+    assert deck_same == deck1
+
+    # Reroll (seed+1) should typically change the result
+    r2 = client.post("/api/random_reroll", json={"seed": base_seed})
+    assert r2.status_code == 200, r2.text
+    d2 = r2.json()
+    assert d2.get("seed") == base_seed + 1
+    deck2 = d2.get("decklist")
+
+    # It is acceptable that a small dataset could still coincide, but in practice should differ
+    assert deck2 != deck1 or d2.get("commander") != d1.get("commander")