add Parseval test

bfps/test/test_Parseval.py

+#! /usr/bin/env python
+
+import os
+import numpy as np
+import h5py
+import sys
+
+import bfps
+from bfps import DNS
+
+def main():
+    niterations = 10
+    c = DNS()
+    c.launch(
+            ['NSVE',
+             '--nx', '32',
+             '--ny', '32',
+             '--nz', '32',
+             '--forcing_type', 'linear',
+             '--np', '4',
+             '--ntpp', '1',
+             '--niter_todo', '{0}'.format(niterations),
+             '--niter_out', '{0}'.format(niterations),
+             '--niter_stat', '1',
+             '--wd', './'] +
+             sys.argv[1:])
+    c.compute_statistics()
+    print(c.statistics['energy(t)'] - c.statistics['renergy(t)'])
+    return None
+
+if __name__ == '__main__':
+    main()
+