127 lines
5.3 KiB
Python
127 lines
5.3 KiB
Python
"""Re-projecting the shelf at a different price.
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The Inventory tab shows COSMOS's forecast at TODAY's price, so a recommendation to raise or
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cut is otherwise displayed with no stock consequence at all. On a SKU near a stockout that is
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the difference between a sound price move and an expensive one.
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The invariants that make this safe to show:
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* a RAISE leaves more stock, a CUT leaves less -- the sign must never invert;
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* week 0 is today's shelf and is untouched by price;
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* arrivals are carried through exactly (a placed PO does not move because we re-priced);
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* stock never goes negative;
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* both cover columns use OUR velocity, so their difference is the price effect alone;
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* bad inputs return [] rather than a fabricated table.
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"""
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from __future__ import annotations
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import pytest
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from dashboard.live_data import reproject_inventory
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def proj(units, arrivals=None, per_unit=4.45, cover=None):
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"""A COSMOS-shaped weekly projection."""
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arrivals = arrivals or [0] * len(units)
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return [{
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"date": f"2026-08-{i + 1:02d}",
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"inventory": u,
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"inventory_value": u * per_unit,
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"cover_days": (cover[i] if cover else None),
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"warehouse_arrival": arrivals[i],
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} for i, u in enumerate(units)]
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# A shelf drawing down 100 units a week from 1,000, on 10 units/day.
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STEADY = proj([1000, 930, 860, 790, 720])
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def test_a_raise_leaves_more_stock_on_the_shelf():
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rows = reproject_inventory(STEADY, units_day_now=10.0, units_day_new=8.0)
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assert rows[-1]["units_new"] > rows[-1]["units_now"]
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assert rows[-1]["delta_units"] > 0
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# ...and monotonically so: every week after the first is at least as good.
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assert all(r["delta_units"] >= 0 for r in rows)
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def test_a_cut_leaves_less_stock_on_the_shelf():
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rows = reproject_inventory(STEADY, units_day_now=10.0, units_day_new=12.0)
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assert rows[-1]["units_new"] < rows[-1]["units_now"]
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assert all(r["delta_units"] <= 0 for r in rows)
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def test_week_zero_is_todays_shelf_and_price_cannot_change_it():
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"""We have not sold anything yet at the new price."""
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for new in (5.0, 10.0, 25.0):
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rows = reproject_inventory(STEADY, 10.0, new)
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assert rows[0]["units_new"] == rows[0]["units_now"] == 1000
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def test_no_change_in_rate_reproduces_cosmos_exactly():
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"""The identity case. If this drifts, every other number here is suspect."""
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rows = reproject_inventory(STEADY, 10.0, 10.0)
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assert [r["units_new"] for r in rows] == [1000, 930, 860, 790, 720]
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assert all(r["delta_units"] == 0 for r in rows)
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def test_arrivals_are_carried_through_untouched():
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"""A purchase order already placed does not move because we re-priced."""
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p = proj([1000, 950, 1400, 1350], arrivals=[0, 0, 500, 0])
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rows = reproject_inventory(p, 10.0, 7.0)
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assert [r["arrival"] for r in rows] == [0, 0, 500, 0]
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# The arrival still lands in full even though the draw around it shrank.
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assert rows[2]["units_new"] > rows[1]["units_new"]
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def test_stock_is_floored_at_zero_and_the_week_is_flagged():
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"""A negative shelf is not a forecast."""
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p = proj([300, 200, 100, 0])
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rows = reproject_inventory(p, 10.0, 40.0) # 4x the burn
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assert all(r["units_new"] >= 0 for r in rows)
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assert any(r["stockout"] for r in rows)
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def test_a_flat_cosmos_projection_has_no_draw_to_rescale():
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"""Real case: COSMOS returns the same 167 units for all 11 weeks on a slow SKU.
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There is no depletion to scale, so units cannot move at any price. The UI says so rather
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than showing an unexplained column of zeros.
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"""
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rows = reproject_inventory(proj([167] * 5), 0.5, 2.0)
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assert all(r["delta_units"] == 0 for r in rows)
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# Cover still responds, because it is computed from our velocity.
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assert rows[0]["cover_new"] < rows[0]["cover_now"]
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def test_both_cover_columns_use_our_velocity_not_cosmos_own():
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"""Mixing bases made a 5% RAISE look like it SHRANK cover, 78 -> 76.
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COSMOS's `coverDays` divides by its own 7-day average; the new column divides by the
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modelled rate. Side by side that difference is the divisor, not the price.
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"""
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p = proj([1000, 930], cover=[78, 72]) # COSMOS's own figures
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rows = reproject_inventory(p, 10.0, 8.0) # a raise: cover must STRETCH
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assert rows[0]["cover_now"] == 100 # 1000 / 10, ours
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assert rows[0]["cover_new"] == 125 # 1000 / 8, ours
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assert rows[0]["cover_new"] > rows[0]["cover_now"]
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# COSMOS's figure is kept alongside, never mixed into the comparison.
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assert rows[0]["cover_cosmos"] == 78
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@pytest.mark.parametrize("projections,now,new", [
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([], 10.0, 8.0), # no projection from COSMOS
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(STEADY, 0.0, 8.0), # no current velocity -> ratio undefined
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(STEADY, 10.0, 0.0), # no projected velocity
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(STEADY, -1.0, 8.0), # nonsense input
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])
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def test_unusable_inputs_return_nothing_rather_than_a_guess(projections, now, new):
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assert reproject_inventory(projections, now, new) == []
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def test_value_stays_on_cosmos_cost_basis():
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"""Scaled with units at COSMOS's own $/unit, not re-derived from our COGS."""
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rows = reproject_inventory(proj([1000, 900], per_unit=4.45), 10.0, 5.0)
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assert rows[0]["value_new"] == pytest.approx(4450, abs=1)
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# week 1 keeps half the draw, so more units and proportionally more value
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assert rows[1]["value_new"] > 900 * 4.45
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