text: # This file is part of QuTiP: Quantum Toolbox in Python.
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  ###############################################################################
  
  import pytest
  import scipy.sparse
  import qutip
  from qutip.fastsparse import fast_csr_matrix
  
  
  class TestOperationEffectsOnType:
      @pytest.mark.parametrize("operation", [
          pytest.param(lambda x: x, id="identity"),
          pytest.param(lambda x: x + x, id="addition"),
          pytest.param(lambda x: x - x, id="subtraction"),
          pytest.param(lambda x: x * x, id="multiplication by op"),
          pytest.param(lambda x: 2*x, id="multiplication by scalar"),
          pytest.param(lambda x: x/3, id="division by scalar"),
          pytest.param(lambda x: -x, id="negation"),
          pytest.param(lambda x: x.copy(), id="copy"),
          pytest.param(lambda x: x.T, id="transpose [.T]"),
          pytest.param(lambda x: x.trans(), id="transpose [.trans()]"),
          pytest.param(lambda x: x.transpose(), id="transpose [.transpose()]"),
          pytest.param(lambda x: x.H, id="adjoint [.H]"),
          pytest.param(lambda x: x.getH(), id="adjoint [.getH()]"),
          pytest.param(lambda x: x.adjoint(), id="adjoint [.adjoint()]"),
      ])
      def test_operations_preserve_type(self, operation):
          op = qutip.rand_herm(5).data
          assert isinstance(operation(op), fast_csr_matrix)
  
      @pytest.mark.parametrize("operation", [
          pytest.param(lambda x, y: y, id="identity of other"),
          pytest.param(lambda x, y: x + y, id="addition"),
          pytest.param(lambda x, y: y + x, id="r-addition"),
          pytest.param(lambda x, y: x - y, id="subtraction"),
          pytest.param(lambda x, y: y - x, id="r-subtraction"),
          pytest.param(lambda x, y: x * y, id="multiplication"),
          pytest.param(lambda x, y: y * x, id="r-multiplication"),
      ])
      def test_mixed_operations_yield_type(self, operation):
          op = qutip.rand_herm(5).data
          other = scipy.sparse.csr_matrix((op.data, op.indices, op.indptr),
                                          copy=True, shape=op.shape)
          assert not isinstance(operation(op, other), fast_csr_matrix)
  