start = new DateTime('2026-01-01'); $this->end = new DateTime('2026-01-31'); }); it('creates a valid period', function (): void { // GIVEN / WHEN $period = new Period( $this->start, $this->end ); // THEN expect($period)->toBeInstanceOf(Period::class) ->and($period->start)->toBe($this->start) ->and($period->end)->toBe($this->end); }); });