Fix failing test in legacy opmath (#6272)

A follow up of #6252, does
the same but with a different test.

tests/transforms/test_diagonalize_measurements.py

@@ -35,6 +35,8 @@
  null_postprocessing,
 )
 
+# pylint: disable=protected-access
+
 
 class TestDiagonalizeObservable:
  """Tests for the _diagonalize_observable method"""
@@ -315,13 +317,9 @@ def test_diagonalize_all_measurements(self, to_eigvals):
  assert isinstance(new_tape.measurements[1], VarianceMP)
  assert new_tape.measurements[0].wires == qml.wires.Wires([0])
  assert new_tape.measurements[1].wires == qml.wires.Wires([1, 2])
+ assert qml.math.allclose(sorted(new_tape.measurements[0]._eigvals), [-1.0, 1.0])
  assert qml.math.allclose(
- sorted(new_tape.measurements[0]._eigvals), # pylint: disable=protected-access
- [-1.0, 1.0],
- )
- assert qml.math.allclose(
- sorted(new_tape.measurements[1]._eigvals), # pylint: disable=protected-access
- [-2.0, 0.0, 0.0, 2.0],
+ sorted(new_tape.measurements[1]._eigvals), [-2.0, 0.0, 0.0, 2.0]
  )
  else:
  assert new_tape.measurements == [qml.expval(Z(0)), qml.var(Z(1) + Z(2))]
@@ -448,11 +446,16 @@ def test_with_duplicate_measurements(self, to_eigvals, supported_base_obs):
  new_tape = tapes[0]
 
  if to_eigvals:
- assert new_tape.measurements == [
- ExpectationMP(eigvals=[1.0, -1], wires=[0]),
- VarianceMP(eigvals=[2.0, 0.0, 0.0, -2.0], wires=[1, 2]),
- SampleMP(eigvals=[1.0, -1.0, -1.0, 1.0], wires=[0, 2]),
- ]
+ assert len(new_tape.measurements) == 3
+ assert isinstance(new_tape.measurements[0], ExpectationMP)
+ assert isinstance(new_tape.measurements[1], VarianceMP)
+ assert isinstance(new_tape.measurements[2], SampleMP)
+ assert new_tape.measurements[0].wires == qml.wires.Wires([0])
+ assert new_tape.measurements[1].wires == qml.wires.Wires([1, 2])
+ assert new_tape.measurements[2].wires == qml.wires.Wires([0, 2])
+ assert np.allclose(sorted(new_tape.measurements[0]._eigvals), [-1.0, 1])
+ assert np.allclose(sorted(new_tape.measurements[1]._eigvals), [-2.0, 0, 0, 2.0])
+ assert np.allclose(sorted(new_tape.measurements[2]._eigvals), [-1.0, -1.0, 1.0, 1.0])
  else:
  assert new_tape.measurements == [
  qml.expval(Z(0)),