intial stage for SplineSmoothing System test

Refs #14082

Testing/SystemTests/tests/analysis/SplineSmoothingTest.py

+import stresstesting
+from mantid.simpleapi import *
+from mantid.api import *
+
+
+
+class SplineSmoothingTest(stresstesting.MantidStressTest):
+    def requiredFiles(self):
+        return ["Stheta.nxs", "ENGINX_precalculated_vanadium_run000236516_bank_curves.nxs"]
+
+    def runTest(self):
+        self._success = False
+
+        wsenginx = Load("ENGINX_precalculated_vanadium_run000236516_bank_curves")
+        SplineSmoothing(InputWorkspace=wsenginx, OutputWorkspace="enginxOutSpline", MaxNumberOfBreaks=20)
+
+        # MaxNumberOfBreaks=0, maximum number of breaking points possible
+        wsStheta = Load("Stheta")
+        SplineSmoothing(InputWorkspace=wsStheta, OutputWorkspace="SthetaOutSpline")
+
+        self._success = True
+
+    def validate(self):
+        return self._success