school_compare/nextjs-app/__tests__/components/CutoffMapPanel.test.tsx

/**
 * The postcode check.
 *
 * This is the one place on the site that answers a question about a specific
 * family rather than about a school, so the tests here are mostly about what it
 * refuses to say — and that matters more now than it did, because there is only
 * one year to answer with. A run of years used to soften a single close call;
 * nothing does now, so the "too close to call" band is the whole safety margin.
 */

import { render, screen, fireEvent, waitFor } from '@testing-library/react';
import { CutoffMapPanel } from '@/components/school/CutoffMapPanel';
import { CUTOFF_UNCERTAINTY_M } from '@/components/school/lastDistanceOffered';
import type { School, SchoolAdmissionDistance } from '@/lib/types';

// Leaflet needs a real layout box and network tiles; neither exists in jsdom.
jest.mock('@/components/LeafletCutoffMapInner', () => ({
  __esModule: true,
  default: () => <div data-testid="cutoff-map" />,
}));

const mockGeocode = jest.fn();
jest.mock('@/lib/api', () => ({
  ...jest.requireActual('@/lib/api'),
  geocodePostcode: (pc: string) => mockGeocode(pc),
}));

const SCHOOL = { urn: 100010, school_name: 'Test Primary', latitude: 51.5, longitude: -0.12 } as School;

const cutoff = (distance_m: number | null, year = 2026): SchoolAdmissionDistance => ({
  year, distance_m, route_count: 1, la_name: 'Camden', distance_unit_raw: 'miles',
});

/** A point due north of the school, `metres` away. 1° latitude ≈ 111,320 m. */
function northOf(metres: number) {
  return { latitude: SCHOOL.latitude! + metres / 111_320, longitude: SCHOOL.longitude! };
}

const renderPanel = (c = cutoff(800)) =>
  render(<CutoffMapPanel schoolInfo={SCHOOL} cutoff={c} />);

async function check(postcode: string) {
  fireEvent.change(screen.getByLabelText('Your postcode'), { target: { value: postcode } });
  fireEvent.click(screen.getByRole('button', { name: 'Check' }));
}

beforeEach(() => mockGeocode.mockReset());

describe('CutoffMapPanel', () => {
  it('renders nothing without a figure to compare against', () => {
    const { container } = renderPanel(cutoff(null));
    expect(container).toBeEmptyDOMElement();
  });

  it('renders nothing when the school has no coordinates', () => {
    const { container } = render(
      <CutoffMapPanel
        schoolInfo={{ ...SCHOOL, latitude: null, longitude: null } as School}
        cutoff={cutoff(800)}
      />,
    );
    expect(container).toBeEmptyDOMElement();
  });

  it('rejects a malformed postcode without calling the geocoder', async () => {
    renderPanel();
    await check('not a postcode');

    expect(await screen.findByRole('alert')).toHaveTextContent(/does not look like a UK postcode/);
    expect(mockGeocode).not.toHaveBeenCalled();
  });

  it('names the year in the verdict, so the figure is never free-floating', async () => {
    mockGeocode.mockResolvedValue(northOf(200));
    renderPanel(cutoff(800, 2026));
    await check('SE23 3NA');

    const result = await screen.findByRole('status');
    expect(result).toHaveTextContent(/inside the/);
    expect(result).toHaveTextContent(/September 2026/);
  });

  it('reports a home clearly beyond the cut-off', async () => {
    mockGeocode.mockResolvedValue(northOf(5000));
    renderPanel(cutoff(800));
    await check('SE23 3NA');

    expect(await screen.findByRole('status')).toHaveTextContent(/beyond the/);
  });

  it('declines to call a result that sits inside the measurement error', async () => {
    // Nominally inside the 800 m cut-off, but by half the uncertainty band —
    // which a postcode centroid cannot resolve. With only one year published
    // there is nothing else to fall back on, so this must not read as a pass.
    mockGeocode.mockResolvedValue(northOf(800 - CUTOFF_UNCERTAINTY_M / 2));
    renderPanel(cutoff(800));
    await check('SE23 3NA');

    const result = await screen.findByRole('status');
    expect(result).toHaveTextContent(/too close/);
    expect(result).toHaveTextContent(/measurement error/);
    // Explanation is supporting text, not part of the bold verdict line.
    expect(result.querySelector('[class*="cutoffCheckHeadline"]')!.textContent)
      .not.toMatch(/measurement error/);
    expect(result).not.toHaveTextContent(/^\S+ away, inside/);
  });

  it('surfaces a postcode the geocoder cannot find', async () => {
    mockGeocode.mockResolvedValue(null);
    renderPanel();
    await check('ZZ99 9ZZ');

    expect(await screen.findByRole('alert')).toHaveTextContent(/could not find that postcode/);
  });

  it('recovers from a geocoder failure instead of leaving a stale verdict', async () => {
    mockGeocode.mockResolvedValue(northOf(200));
    renderPanel();
    await check('SE23 3NA');
    await screen.findByRole('status');

    mockGeocode.mockRejectedValue(new Error('network'));
    await check('SE23 3NB');

    await waitFor(() => expect(screen.queryByRole('status')).not.toBeInTheDocument());
    expect(screen.getByRole('alert')).toHaveTextContent(/Something went wrong/);
  });

  it('keeps the map behind a request until there is a reason to show it', async () => {
    renderPanel();
    expect(screen.queryByTestId('cutoff-map')).not.toBeInTheDocument();

    mockGeocode.mockResolvedValue(northOf(200));
    await check('SE23 3NA');
    await screen.findByRole('status');
    expect(screen.getByTestId('cutoff-map')).toBeInTheDocument();
  });

  it('can also show the map without a postcode, on request', () => {
    renderPanel();
    fireEvent.click(screen.getByRole('button', { name: /Show this distance on a map/ }));
    expect(screen.getByTestId('cutoff-map')).toBeInTheDocument();
  });

  it('states its limits before it is used, not with the answer', () => {
    renderPanel();
    const caveat = screen.getByText(/Distance is the last criterion applied/);
    expect(caveat).toBeInTheDocument();
    expect(caveat).toHaveTextContent(/not a catchment boundary/);
    expect(caveat).toHaveTextContent(/walking route/);
  });
});