TEST: Test sv cache invalidation after write when using spline interpolation

test/test_shadwovolume_cache.cc

@@ -110,3 +110,25 @@ BOOST_FIXTURE_TEST_CASE(test_reinitialize, F)
     check_close(sum, testsums[t]);
   }
 }
+
+// check that sv cache is invalidated on
+// writes when using spline interpolation
+BOOST_FIXTURE_TEST_CASE(test_splinterp, F)
+{
+  testvol.setinterpolationmethod(spline);
+
+  for (int t = 0; t < tsz; t++) {
+
+    volume<float> evalvol = testvol[t];
+    evalvol.setinterpolationmethod(spline);
+
+    check_close(evalvol   .interpolate(5, 5, 5),
+                testvol[t].interpolate(5, 5, 5));
+
+    testvol(5, 5, 5, t) = 12345;
+    evalvol(5, 5, 5)    = 12345;
+
+    check_close(evalvol   .interpolate(5, 5, 5),
+                testvol[t].interpolate(5, 5, 5));
+  }
+}