test_session_epoch.py

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"""A recreated backend session is recognisable, so the design bar never autosaves its default.
 
2026-10-01: a backend restart left the session holding configs/default.yaml (methalox); the design
bar's autosave read it as an edit and saved it over an ethalox design. The bar now compares the
session epoch it loaded the design into with the one the backend reports, and restores the design
when they differ. This guards the backend half: every session object has its own epoch, and the
config routes the bar reads report it.
"""
import os
import sys
 
sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
from fastapi import FastAPI  # noqa: E402
from fastapi.testclient import TestClient  # noqa: E402
 
from backend.session import UserSession, get_session  # noqa: E402
 
 
def test_every_session_has_its_own_epoch():
    a, b = UserSession("epoch-a"), UserSession("epoch-a")
    assert a.epoch and b.epoch and a.epoch != b.epoch
 
 
def test_the_config_routes_report_the_epoch():
    from backend.routers import config as config_router
 
    session = UserSession("epoch-b")
    app = FastAPI()
    app.include_router(config_router.router)
    app.dependency_overrides[get_session] = lambda: session
    client = TestClient(app)
    got = client.get("/api/config").json()
    assert got["session_epoch"] == session.epoch
    loaded = client.post("/api/config/load", json=got["config"]).json()
    assert loaded["session_epoch"] == session.epoch
 
 
def test_a_wholesale_load_is_stamped_so_another_tab_can_tell_it_is_not_its_own():
    """The session is one per user and every tab shares it. Tab B opening design X POSTs X over
    the design Y tab A holds; A's autosave then read X as an edit and saved it into Y. Every
    wholesale load now gets a fresh token, and a fresh session has none (only the default is in
    it), so A can refuse to autosave a config it did not load, and a read-only tab can tell a
    default it may replace from another tab's design it must not."""
    from backend.routers import config as config_router
 
    session = UserSession("epoch-c")
    app = FastAPI()
    app.include_router(config_router.router)
    app.dependency_overrides[get_session] = lambda: session
    client = TestClient(app)
    got = client.get("/api/config").json()
    assert got["load_token"] is None  # nobody has loaded anything: the default
    first = client.post("/api/config/load", json=got["config"]).json()["load_token"]
    assert first and client.get("/api/config").json()["load_token"] == first
    second = client.post("/api/config/load", json=got["config"]).json()["load_token"]
    assert second and second != first
    # An edit is not a load: the tab that holds the design keeps its token through a PUT.
    client.put("/api/config", json={})
    assert client.get("/api/config").json()["load_token"] == second