class_docstr: Test Evolution(Exp) class that takes a parameter x and a generator G and defines an evolution exp(ixG)
docstr: Tests that an error is raised if the generator of an Evolution operator is requested
  with a non-zero complex term in the operator parameter.
docstr_tok: ["Tests","that","an","error","is","raised","if","the","generator","of","an","Evolution","operator","is","requested","with","a","non-zero","complex","term","in","the","operator","parameter","."]
code: def test_generator_undefined_error(self):
      """Tests that an error is raised if the generator of an Evolution operator is requested
      with a non-zero complex term in the operator parameter."""
      param = 1 + 2.5j
      op = Evolution(qml.PauliZ(0), param)
  
      with pytest.raises(
          qml.operation.GeneratorUndefinedError,
          match="is not imaginary; the expected format is exp",
      ):
          _ = op.generator()
  
imports: import pytest
  import pennylane
  from pennylane import numpy
  from pennylane.ops.op_math import Evolution, Exp
label_desc: Use image node_id 19 for calling the TestEvolution obj's underlying member method code with example usage: obj.test_generator_undefined_error() without return types