test(01-02): add failing tests for InlineEditCell

- renders formatted currency in display mode
- enters edit mode on click
- calls onSave with parsed number on blur/Enter
- does not call onSave when value unchanged

frontend/src/components/InlineEditCell.test.tsx

@@ -0,0 +1,106 @@
+import { render, screen, fireEvent } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { InlineEditCell } from './InlineEditCell'
+
+// Wrap in a table/row to satisfy semantic HTML for TableCell
+function Wrapper({ children }: { children: React.ReactNode }) {
+  return (
+    <table>
+      <tbody>
+        <tr>{children}</tr>
+      </tbody>
+    </table>
+  )
+}
+
+describe('InlineEditCell', () => {
+  const defaultProps = {
+    value: 42.5,
+    currency: 'EUR',
+    onSave: vi.fn().mockResolvedValue(undefined),
+  }
+
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('renders formatted currency value in display mode', () => {
+    render(
+      <Wrapper>
+        <InlineEditCell {...defaultProps} />
+      </Wrapper>
+    )
+    // Should show formatted value (42.5 in EUR → some formatted string containing 42)
+    expect(screen.getByText(/42/)).toBeInTheDocument()
+  })
+
+  it('enters edit mode on click', async () => {
+    const user = userEvent.setup()
+    render(
+      <Wrapper>
+        <InlineEditCell {...defaultProps} />
+      </Wrapper>
+    )
+    const span = screen.getByText(/42/)
+    await user.click(span)
+    // After click, an input should be visible
+    expect(screen.getByRole('spinbutton')).toBeInTheDocument()
+  })
+
+  it('calls onSave with parsed number on blur', async () => {
+    const user = userEvent.setup()
+    const onSave = vi.fn().mockResolvedValue(undefined)
+    render(
+      <Wrapper>
+        <InlineEditCell {...defaultProps} onSave={onSave} />
+      </Wrapper>
+    )
+    const span = screen.getByText(/42/)
+    await user.click(span)
+
+    const input = screen.getByRole('spinbutton')
+    await user.clear(input)
+    await user.type(input, '100')
+    fireEvent.blur(input)
+
+    expect(onSave).toHaveBeenCalledWith(100)
+  })
+
+  it('does not call onSave when value unchanged', async () => {
+    const user = userEvent.setup()
+    const onSave = vi.fn().mockResolvedValue(undefined)
+    render(
+      <Wrapper>
+        <InlineEditCell {...defaultProps} onSave={onSave} />
+      </Wrapper>
+    )
+    const span = screen.getByText(/42/)
+    await user.click(span)
+
+    // Don't change the value, just blur
+    const input = screen.getByRole('spinbutton')
+    fireEvent.blur(input)
+
+    expect(onSave).not.toHaveBeenCalled()
+  })
+
+  it('calls onSave on Enter key', async () => {
+    const user = userEvent.setup()
+    const onSave = vi.fn().mockResolvedValue(undefined)
+    render(
+      <Wrapper>
+        <InlineEditCell {...defaultProps} onSave={onSave} />
+      </Wrapper>
+    )
+    const span = screen.getByText(/42/)
+    await user.click(span)
+
+    const input = screen.getByRole('spinbutton')
+    await user.clear(input)
+    await user.type(input, '99')
+    await user.keyboard('{Enter}')
+
+    expect(onSave).toHaveBeenCalledWith(99)
+  })
+})