A try of overhauling the frontend tests, bailed after 24h+

frontend/tests/unit/components/tracker/TimeAdjuster.test.tsx

@@ -0,0 +1,53 @@
+import { render, screen, fireEvent } from '@testing-library/react';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import TimeAdjuster from '../../../../src/components/tracker/TimeAdjuster';
+
+// Mock time utils to avoid timezone issues in tests
+vi.mock('../../../src/utils/time', () => ({
+  toLocalDatetimeInputValue: vi.fn((d) => d.toISOString().slice(0, 16)),
+  toUTCFromLocalInput: vi.fn((val) => val), // simple identity for testing
+}));
+
+describe('TimeAdjuster', () => {
+  const onChange = vi.fn();
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('renders with default value if provided', () => {
+    const defaultValue = '2024-01-01T12:00';
+    render(<TimeAdjuster onTimeChange={onChange} defaultValue={defaultValue} />);
+
+    const input = screen.getByLabelText(/Time/i) as HTMLInputElement;
+    expect(input.value).toBe(defaultValue);
+  });
+
+  it('calls onTimeChange when input value changes', async () => {
+    render(<TimeAdjuster onTimeChange={onChange} />);
+
+    const input = screen.getByLabelText(/Time/i) as HTMLInputElement;
+    fireEvent.change(input, { target: { value: '2024-01-01T13:00' } });
+
+    expect(onChange).toHaveBeenLastCalledWith('2024-01-01T12:00:00.000Z');
+  });
+
+  it('resets to now when reset button is clicked', () => {
+    const mockNow = new Date('2024-01-01T10:00:00');
+    vi.useFakeTimers();
+    vi.setSystemTime(mockNow);
+
+    render(<TimeAdjuster onTimeChange={onChange} />);
+    
+    const resetButton = screen.getByText(/Reset to now/i);
+    fireEvent.click(resetButton);
+
+    const input = screen.getByLabelText(/Time/i) as HTMLInputElement;
+    // The component calls toLocalDatetimeInputValue(new Date())
+    // Our mock returns the iso string slice.
+    expect(input.value).toBe('2024-01-01T10:00');
+    expect(onChange).toHaveBeenCalled();
+
+    vi.useRealTimers();
+  });
+});