public function test_nullable_timestamps()
 {
     $column = m::mock(Column::class);
     $this->dbal->shouldReceive('addColumn')->with('created_at', 'datetime')->andReturn($column);
     $this->dbal->shouldReceive('addColumn')->with('updated_at', 'datetime')->andReturn($column);
     $column->shouldReceive('setNotnull')->with(false)->twice();
     $this->table->nullableTimestamps();
 }