Add type and value checking to Integrators

- SI_Integrator must be passed positive integer.
- Number of powers computed must be equal to the
  number of time steps

Added unit test to ensure that the right errors are raised.

openmc/deplete/integrator/abc.py

@@ -1,9 +1,11 @@
 from copy import deepcopy
 from abc import ABC, abstractmethod
 from collections.abc import Iterable
+from numbers import Integral
 
 from uncertainties import ufloat
 
+from openmc.checkvalue import check_type, check_greater_than
 from openmc.capi import statepoint_write
 from openmc.deplete import Results, OperatorResult
 
@@ -60,9 +62,12 @@ class Integrator(ABC):
                 power = [p * operator.heavy_metal for p in power_density]
 
         if not isinstance(power, Iterable):
-            # TODO Maybe use itertools.zip_longest?
             # Ensure that power is single value if that is the case
             power = [power] * len(self.timesteps)
+        elif len(power) != len(self.timesteps):
+            raise ValueError(
+                "Number of time steps != number of powers. {} vs {}".format(
+                    len(self.timesteps), len(power)))
 
         self.power = power
 
@@ -208,8 +213,10 @@ class SI_Integrator(Integrator):
             is not speficied.
         n_steps : int, optional
             Number of stochastic iterations per depletion interval.
-            Default : 10
+            Must be greater than zero. Default : 10
         """
+        check_type("n_steps", n_steps, Integral)
+        check_greater_than("n_steps", n_steps, 0)
         super().__init__(operator, timesteps, power, power_density)
         self.n_steps = n_steps
 

tests/unit_tests/test_deplete_integrator.py

@@ -12,9 +12,11 @@ from unittest.mock import MagicMock
 
 import numpy as np
 from uncertainties import ufloat
+import pytest
 
-from openmc.deplete import (ReactionRates, Results, ResultsList, comm,
-                            OperatorResult)
+from openmc.deplete import (
+    ReactionRates, Results, ResultsList, comm, OperatorResult,
+    PredictorIntegrator, SI_CELI_Integrator)
 
 
 def test_results_save(run_in_tmpdir):
@@ -99,3 +101,32 @@ def test_results_save(run_in_tmpdir):
 
     np.testing.assert_array_equal(res[1].k, eigvl2)
     np.testing.assert_array_equal(res[1].time, t2)
+
+
+@pytest.mark.parametrize("timesteps", (1, [1]))
+def test_bad_integrator_inputs(timesteps):
+    """Test failure modes for Integrator inputs"""
+
+    op = MagicMock()
+    op.prev_res = None
+    op.chain = None
+    op.heavy_metal = 1.0
+
+    # No power nor power density given
+    with pytest.raises(ValueError, match="Either power or power density"):
+        PredictorIntegrator(op, timesteps)
+
+    # Length of power != length time
+    with pytest.raises(ValueError, match="number of powers"):
+        PredictorIntegrator(op, timesteps, power=[1, 2])
+
+    # Length of power density != length time
+    with pytest.raises(ValueError, match="number of powers"):
+        PredictorIntegrator(op, timesteps, power_density=[1, 2])
+
+    # SI integrator with bad steps
+    with pytest.raises(TypeError, match="n_steps"):
+        SI_CELI_Integrator(op, timesteps, [1], n_steps=2.5)
+
+    with pytest.raises(ValueError, match="n_steps"):
+        SI_CELI_Integrator(op, timesteps, [1], n_steps=0)