before functional changes by codex

test/basic/pfr-operators.basic.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');
+
+test('Reactor_PFR derivative operators have expected dimensions and boundary rows', () => {
+  const reactor = new Reactor_PFR(
+    makeReactorConfig({
+      reactor_type: 'PFR',
+      length: 12,
+      resolution_L: 6,
+      volume: 60,
+      n_inlets: 1,
+    }),
+  );
+
+  assert.equal(reactor.D_op.length, reactor.n_x);
+  assert.equal(reactor.D2_op.length, reactor.n_x);
+  assert.equal(reactor.D_op.every((row) => row.length === reactor.n_x), true);
+  assert.equal(reactor.D2_op.every((row) => row.length === reactor.n_x), true);
+
+  assert.deepEqual(reactor.D_op[0], Array(reactor.n_x).fill(0));
+  assert.deepEqual(reactor.D_op[reactor.n_x - 1], Array(reactor.n_x).fill(0));
+  assert.deepEqual(reactor.D2_op[0], Array(reactor.n_x).fill(0));
+  assert.deepEqual(reactor.D2_op[reactor.n_x - 1], Array(reactor.n_x).fill(0));
+});