Expand React race hub analytics

frontend/src/test/TabBar.test.tsx

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+import { describe, it, expect, vi } from 'vitest'
+import { render, screen, fireEvent } from '@testing-library/react'
+import { TabBar } from '../components/TabBar'
+
+describe('TabBar', () => {
+  it('renders all 5 tabs', () => {
+    render(<TabBar active="results" onChange={() => {}} />)
+    expect(screen.getByRole('tab', { name: 'Results' })).toBeInTheDocument()
+    expect(screen.getByRole('tab', { name: 'Grid' })).toBeInTheDocument()
+    expect(screen.getByRole('tab', { name: 'Strategy' })).toBeInTheDocument()
+    expect(screen.getByRole('tab', { name: 'Positions' })).toBeInTheDocument()
+    expect(screen.getByRole('tab', { name: 'Datasets' })).toBeInTheDocument()
+  })
+
+  it('marks the active tab with aria-selected', () => {
+    render(<TabBar active="grid" onChange={() => {}} />)
+    expect(screen.getByRole('tab', { name: 'Grid' })).toHaveAttribute('aria-selected', 'true')
+    expect(screen.getByRole('tab', { name: 'Results' })).toHaveAttribute('aria-selected', 'false')
+  })
+
+  it('applies active class only to the active tab', () => {
+    render(<TabBar active="strategy" onChange={() => {}} />)
+    const strategy = screen.getByRole('tab', { name: 'Strategy' })
+    const results = screen.getByRole('tab', { name: 'Results' })
+    expect(strategy.className).toContain('active')
+    expect(results.className).not.toContain('active')
+  })
+
+  it('calls onChange with the correct tab id when clicked', () => {
+    const onChange = vi.fn()
+    render(<TabBar active="results" onChange={onChange} />)
+    fireEvent.click(screen.getByRole('tab', { name: 'Datasets' }))
+    expect(onChange).toHaveBeenCalledWith('datasets')
+  })
+})