function testDeleteAll() { //Arrange $book_id = 1; $due_date = '0000-00-00'; $id = 1; $test_copy = new Copy($book_id, $due_date, $id); $test_copy->save(); $book_id2 = 2; $due_date2 = '0000-00-00'; $id2 = 2; $test_copy2 = new Copy($book_id2, $due_date2, $id2); $test_copy2->save(); //Act Copy::deleteALl(); //Assert $result = Copy::getAll(); $this->assertEquals([], $result); }