fix(packing): the weight field keeps what is typed and saves it once, on blur or Enter, instead of a fragment per keystroke on a slow connection (#3005)

client/src/components/Packing/PackingListPanelWeightInput.test.tsx

@@ -0,0 +1,78 @@
+// FE-COMP-PACKING-095 to FE-COMP-PACKING-098
+import { useState } from 'react';
+import { vi } from 'vitest';
+import { fireEvent, render, screen, waitFor } from '../../../tests/helpers/render';
+import { WeightInput } from './PackingListPanelWeightInput';
+
+/** A row whose stored weight changes only once a save answers, as the store does. */
+function SlowRow({ onSave }: { onSave: (grams: number | null) => void }) {
+  const [stored, setStored] = useState<number | null>(null);
+  return (
+    <WeightInput
+      value={stored}
+      width={36}
+      onSave={async (grams) => {
+        onSave(grams);
+        await new Promise((resolve) => setTimeout(resolve, 300));
+        setStored(grams);
+      }}
+    />
+  );
+}
+
+describe('WeightInput', () => {
+  it('FE-COMP-PACKING-095: #3005 keeps every typed digit and saves the whole weight once', async () => {
+    const onSave = vi.fn();
+    render(<SlowRow onSave={onSave} />);
+    const input = screen.getByRole('textbox') as HTMLInputElement;
+
+    fireEvent.focus(input);
+    for (const typed of ['2', '25', '250']) {
+      fireEvent.change(input, { target: { value: typed } });
+      expect(input.value).toBe(typed);
+    }
+    expect(onSave).not.toHaveBeenCalled();
+
+    fireEvent.blur(input);
+    expect(onSave).toHaveBeenCalledTimes(1);
+    expect(onSave).toHaveBeenCalledWith(250);
+    await waitFor(() => expect(input.value).toBe('250'));
+  });
+
+  it('FE-COMP-PACKING-096: saves on Enter and stores an empty field as no weight', () => {
+    const onSave = vi.fn();
+    render(<WeightInput value={300} width={36} onSave={onSave} />);
+    const input = screen.getByRole('textbox') as HTMLInputElement;
+
+    input.focus();
+    fireEvent.focus(input);
+    fireEvent.change(input, { target: { value: '' } });
+    fireEvent.keyDown(input, { key: 'Enter' });
+
+    expect(onSave).toHaveBeenCalledWith(null);
+  });
+
+  it('FE-COMP-PACKING-097: leaves an unchanged weight alone and follows a change from elsewhere', () => {
+    const onSave = vi.fn();
+    const { rerender } = render(<WeightInput value={300} width={36} onSave={onSave} />);
+    const input = screen.getByRole('textbox') as HTMLInputElement;
+
+    fireEvent.focus(input);
+    fireEvent.blur(input);
+    expect(onSave).not.toHaveBeenCalled();
+
+    rerender(<WeightInput value={450} width={36} onSave={onSave} />);
+    expect(input.value).toBe('450');
+  });
+
+  it('FE-COMP-PACKING-098: a read-only field never saves', () => {
+    const onSave = vi.fn();
+    render(<WeightInput value={300} width={36} readOnly onSave={onSave} />);
+    const input = screen.getByRole('textbox') as HTMLInputElement;
+
+    fireEvent.change(input, { target: { value: '9' } });
+    fireEvent.blur(input);
+
+    expect(onSave).not.toHaveBeenCalled();
+  });
+});