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

/**
 * The section's job is to be honest about what it matched. These tests pin the
 * ways it could lie: rendering below the minimum, claiming a similar intake at
 * tier 3, showing a missing figure as a number, or hiding a card behind an
 * arrow where a crawler cannot reach it.
 */

import { render, screen } from '@testing-library/react';

import {
  SimilarSchoolsSection,
  shouldRenderSimilar,
} from '@/components/school/SimilarSchoolsSection';
import type { SimilarSchool } from '@/lib/types';

jest.mock('@/components/school/AddToCompareButton', () => ({
  AddToCompareButton: ({ school }: { school: SimilarSchool }) => (
    <button type="button">Add {school.school_name} to compare</button>
  ),
}));

jest.mock('@/components/school/SimilarSchoolsCompareBar', () => ({
  SimilarSchoolsCompareBar: ({ thisUrn }: { thisUrn: number }) => (
    <div data-testid="compare-bar">bar for {thisUrn}</div>
  ),
}));

function school(overrides: Partial<SimilarSchool> = {}): SimilarSchool {
  return {
    urn: 100002,
    school_name: 'Willow Lane Primary School',
    distance_miles: 0.6,
    school_type: 'Community school',
    age_range: '4-11',
    shared: ['Mixed', 'No religious character'],
    tier: 1,
    metric_value: 74,
    metric_key: 'rwm_expected_pct',
    metric_year: 202425,
    ...overrides,
  };
}

function renderSection(similar: SimilarSchool[]) {
  return render(
    <SimilarSchoolsSection
      urn={100001}
      schoolName="Meadowbrook Primary School"
      phaseNoun="primary"
      thisMetricValue={72}
      similar={similar}
    />,
  );
}

describe('render gates', () => {
  it.each([
    ['undefined', undefined],
    ['null', null],
    ['empty', []],
    ['a single school', [school()]],
  ])('renders nothing for %s', (_label, value) => {
    expect(shouldRenderSimilar(value as SimilarSchool[] | null | undefined)).toBe(false);
  });

  it('renders for two or more schools', () => {
    expect(shouldRenderSimilar([school(), school({ urn: 100003 })])).toBe(true);
  });

  it('returns null rather than an empty shell below the minimum', () => {
    const { container } = renderSection([school()]);
    expect(container).toBeEmptyDOMElement();
  });
});

describe('the claim the lede makes', () => {
  it('claims a similar intake when every card is tier 1 or 2', () => {
    renderSection([school({ tier: 1 }), school({ urn: 100003, tier: 2 })]);
    expect(screen.getByText(/with a similar intake/i)).toBeInTheDocument();
  });

  it('drops the claim when any card is tier 3', () => {
    renderSection([school({ tier: 1 }), school({ urn: 100003, tier: 3, shared: ['Primary school'] })]);
    expect(screen.queryByText(/with a similar intake/i)).not.toBeInTheDocument();
  });
});

describe('cards', () => {
  it('links each school to its canonical slug', () => {
    renderSection([school(), school({ urn: 100003, school_name: 'Oakfield Primary School' })]);
    const link = screen.getByRole('link', { name: /Willow Lane Primary School/ });
    expect(link).toHaveAttribute('href', '/school/100002-willow-lane-primary-school');
  });

  it('shows the distance and the shared characteristics', () => {
    renderSection([school(), school({ urn: 100003 })]);
    expect(screen.getAllByText('0.6 miles away').length).toBeGreaterThan(0);
    expect(screen.getAllByText('Mixed').length).toBeGreaterThan(0);
  });

  it('renders a missing figure as "Not published", never as a number', () => {
    renderSection([school({ metric_value: null }), school({ urn: 100003 })]);
    expect(screen.getByText('Not published')).toBeInTheDocument();
  });

  it('anchors each figure against this school', () => {
    renderSection([school(), school({ urn: 100003 })]);
    expect(screen.getAllByText('72% at this school').length).toBe(2);
  });

  it('offers the compare bar once, for this school', () => {
    renderSection([school(), school({ urn: 100003 })]);
    expect(screen.getByTestId('compare-bar')).toHaveTextContent('bar for 100001');
  });

  it('keeps every card in the DOM, including the ones scrolled out of view', () => {
    const six = Array.from({ length: 6 }, (_, n) =>
      school({ urn: 100002 + n, school_name: `Peer ${n} School` }),
    );
    renderSection(six);
    expect(screen.getAllByRole('link', { name: /Peer \d School/ })).toHaveLength(6);
  });

  it('offers no arrows when three cards fit the row', () => {
    renderSection([school(), school({ urn: 100003 }), school({ urn: 100004 })]);
    expect(screen.queryByRole('button', { name: /More schools/ })).not.toBeInTheDocument();
  });

  it('offers arrows once there is a fourth school', () => {
    renderSection(Array.from({ length: 4 }, (_, n) => school({ urn: 100002 + n })));
    expect(screen.getByRole('button', { name: /More schools/ })).toBeInTheDocument();
    expect(screen.getByRole('button', { name: /Previous schools/ })).toBeInTheDocument();
  });

  it('says distances are straight-line, and offers no method panel', () => {
    const { container } = renderSection([school(), school({ urn: 100003 })]);
    expect(screen.getByText(/straight-line from this school/i)).toBeInTheDocument();
    expect(container.querySelector('details')).toBeNull();
  });
});