before functional changes by codex

test/edge/zero-dispersion.edge.test.js

@@ -0,0 +1,27 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const { Reactor_PFR } = require('../../src/specificClass');
+const { makeReactorConfig } = require('../helpers/factories');
+
+const DAY_MS = 1000 * 60 * 60 * 24;
+
+test('updateState warns when local Peclet number is too high at zero dispersion', () => {
+  const reactor = new Reactor_PFR(
+    makeReactorConfig({ reactor_type: 'PFR', length: 10, resolution_L: 5, volume: 50, n_inlets: 1 }),
+  );
+
+  const warnings = [];
+  reactor.logger.warn = (msg) => warnings.push(String(msg));
+
+  reactor.currentTime = 0;
+  reactor.timeStep = 1;
+  reactor.speedUpFactor = 1;
+  reactor.Fs[0] = 2;
+  reactor.D = 0;
+  reactor.tick = () => reactor.state;
+
+  reactor.updateState(DAY_MS);
+
+  assert.equal(warnings.some((w) => w.includes('Péclet number') || w.includes('Peclet number')), true);
+});