feat: add durable WorldQuant backtests with UI and AI confirmation

backend/tests/backtest_fake.py

@@ -0,0 +1,88 @@
+"""Synthetic simulation HTTP used by isolated API and browser acceptance."""
+
+import json
+
+import httpx
+
+
+class Platform:
+    def __init__(self):
+        self.posts = []
+        self.existing_alpha_ids = None
+        self.simulations = {}
+        self.alphas = {}
+        self.reject = None
+        self.pending = False
+        self.detail_fail = False
+        self.fail_child = None
+        self.missing = False
+        self.secret = "synthetic-platform-secret"
+
+    def __call__(self, request):
+        path = request.url.path
+        if path == "/authentication":
+            return httpx.Response(201, json={})
+        if path == "/simulations" and request.method == "POST":
+            data = json.loads(request.content)
+            data = data if isinstance(data, list) else [data]
+            self.posts.append(data)
+            if self.reject == "unknown":
+                raise httpx.ReadTimeout("synthetic timeout", request=request)
+            if self.reject == "session":
+                self.reject = None
+                return httpx.Response(401)
+            if self.reject == "rate":
+                return httpx.Response(429, headers={"Retry-After": "0.01"})
+            if self.reject == "bad":
+                return httpx.Response(400, json={"error": self.secret})
+            parent = f"p{len(self.posts)}"
+            ids = []
+            for i, item in enumerate(data):
+                child = parent if len(data) == 1 else f"{parent}c{i}"
+                aid = self.existing_alpha_ids[i] if self.existing_alpha_ids else f"alpha{parent}{i}"
+                progress = {
+                    "status": "COMPLETE",
+                    "alpha": aid,
+                    "regular": item["regular"],
+                    "settings": item["settings"],
+                }
+                if i == self.fail_child:
+                    progress = {
+                        "status": "FAILED",
+                        "regular": item["regular"],
+                        "settings": item["settings"],
+                        "message": "invalid expression",
+                    }
+                self.simulations[child] = progress
+                self.alphas[aid] = {
+                    "id": aid,
+                    "regular": {"code": item["regular"]},
+                    "type": "REGULAR",
+                    "settings": item["settings"],
+                    "is": {"sharpe": None, "fitness": 0.8},
+                    "status": "UNSUBMITTED",
+                }
+                ids.append(child)
+            if len(data) > 1:
+                self.simulations[parent] = {
+                    "status": "COMPLETE",
+                    "children": list(reversed(ids[1:] if self.missing else ids)),
+                }
+            if self.reject == "missing_location":
+                return httpx.Response(201)
+            return httpx.Response(
+                201, headers={"Location": f"https://api.worldquantbrain.com/simulations/{parent}"}
+            )
+        if path.startswith("/simulations/"):
+            return httpx.Response(
+                200, json={"status": "PENDING"} if self.pending else self.simulations[path.rsplit("/", 1)[-1]]
+            )
+        if path.startswith("/alphas/"):
+            if self.detail_fail:
+                return httpx.Response(404)
+            return httpx.Response(200, json=self.alphas[path.rsplit("/", 1)[-1]])
+        if path == "/users/self":
+            return httpx.Response(200, json={"id": "TEST_USER"})
+        if path.startswith("/users/self/"):
+            return httpx.Response(200, json={"results": [], "count": 0})
+        raise AssertionError(f"Unexpected HTTP {request.method} {path}")