fix: Changing prices and dynamics in revenus

tests/engine.test.js

@@ -165,15 +165,56 @@ test('material is costly at first and cheaper relative to the sale price as prod
   assert.ok(costShare(1e9) < 0.1, 'a small share of revenue late in the game');
 });
 
-test('material lots grow with the operation, in doublings', () => {
-  const sizeAt = (total) => {
+test('material lots follow current output, in doublings', () => {
+  const sizeWith = (gen1) => {
     const s = fresh();
-    s.totalProduced = total;
+    s.generators.gen1 = gen1;
     return derive(s, ctx).batchSize;
   };
-  assert.equal(sizeAt(0), ctx.rules.materialMarket.minBatch);
-  assert.ok(sizeAt(1e6) > sizeAt(1e4));
-  assert.equal(Math.log2(sizeAt(1e6) / ctx.rules.materialMarket.minBatch) % 1, 0);
+  const { minBatch } = ctx.rules.materialMarket;
+  assert.equal(sizeWith(0), minBatch);
+  assert.ok(sizeWith(500) > sizeWith(5));
+  assert.equal(Math.log2(sizeWith(500) / minBatch) % 1, 0);
+});
+
+test('stack upgrades multiply the lot, and its price grows in proportion', () => {
+  const lot = (upgrades) => {
+    const s = fresh();
+    s.upgrades = upgrades;
+    s.materialFactor = 1;
+    return derive(s, ctx);
+  };
+  const base = lot([]);
+  const doubled = lot(['stack_1']);
+  const x12 = lot(['stack_1', 'stack_2', 'stack_3']);
+  assert.equal(doubled.batchSize, base.batchSize * 2);
+  assert.equal(x12.batchSize, base.batchSize * 12);
+  assert.ok(Math.abs(doubled.batchCost - base.batchCost * 2) <= 0.01, 'twice the wire costs twice as much');
+  assert.ok(Math.abs(x12.batchCost - base.batchCost * 12) <= 0.06);
+});
+
+test('the price PER UNIT of material is unchanged by stack size and keeps falling with scale', () => {
+  const unitPrice = (totalProduced, upgrades) => {
+    const s = fresh();
+    s.totalProduced = totalProduced;
+    s.upgrades = upgrades;
+    s.materialFactor = 1;
+    const d = derive(s, ctx);
+    return d.batchCost / d.batchSize;
+  };
+  const early = unitPrice(0, []);
+  assert.ok(Math.abs(unitPrice(0, ['stack_1', 'stack_2']) - early) < early * 0.01);
+  assert.ok(unitPrice(1e6, ['stack_1', 'stack_2']) < unitPrice(1e4, ['stack_1', 'stack_2']));
+  assert.ok(unitPrice(1e9, []) < early / 5, 'much cheaper per unit late in the game');
+});
+
+test('stack upgrades form a chain', () => {
+  const s = fresh();
+  s.totalProduced = 1e9;
+  assert.ok(upgradeVisible(s, ctx.upgradesById.get('stack_1')));
+  assert.equal(upgradeVisible(s, ctx.upgradesById.get('stack_2')), false);
+  s.upgrades = ['stack_1'];
+  assert.ok(upgradeVisible(s, ctx.upgradesById.get('stack_2')));
 });
 
 test('the material market is erratic but stays within its bounds', () => {