text: """Tests for stack module."""
  import pytest
  
  
  def test_stack_type():
      """Test stack instance type."""
      from stack import Stack
      stck = Stack()
      assert type(stck) == Stack
  
  
  def test_push_and_pop():
      """Test the push and pop method on stack."""
      from stack import Stack
      stck = Stack()
      stck.push('one')
      stck.push('two')
      assert stck.pop() == 'two'
  
  
  def test_stack_len():
      """Test the len function on stack."""
      from stack import Stack
      stck = Stack()
      stck.push('one')
      stck.push('two')
      assert len(stck) == 2
  
  
  def test_pop_from_empty_stack_raises_error():
      """Test IndexError raised when pop from empty stack."""
      from stack import Stack
      stck = Stack()
      with pytest.raises(IndexError):
          stck.pop()
  