refactor(app): share application components and request services

src/app/sourceSlot.test.mjs

@@ -0,0 +1,24 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { createSourceSlot } from './sourceSlot.js';
+
+test('replacing a source rejects its late result and old cleanup cannot clear the new source', async () => {
+  let finish;
+  const slot = createSourceSlot({ read: async () => 'default' }, ['read']);
+  const old = slot.configure({ read: () => new Promise(resolve => { finish = resolve; }) });
+  const pending = slot.source.read();
+  const stop = slot.configure({ read: async () => 'replacement', attribution: { name: 'Replacement' } });
+  old();
+  finish('stale');
+  await assert.rejects(pending, { name: 'AbortError' });
+  assert.equal(await slot.source.read(), 'replacement');
+  assert.equal(slot.source.attribution.name, 'Replacement');
+  stop();
+  assert.throws(() => slot.source.read(), /not configured/);
+});
+
+test('an invalid replacement leaves the working source intact', async () => {
+  const slot = createSourceSlot({ read: async () => 42 }, ['read']);
+  assert.throws(() => slot.configure({}), TypeError);
+  assert.equal(await slot.source.read(), 42);
+});