Tests: Do not reuse a filename

dune/fufem/test/test-hdf5.cc

@@ -65,7 +65,7 @@ template <class Vector>
 bool checkAddSequence(Vector const &written0, Vector const &written1) {
   bool passed = true;
   using ft = typename Vector::block_type::field_type;
-  std::string const filename("out-sequence.h5");
+  std::string const filename("out-sequence-add.h5");
   {
     deleteIfNecessary(filename);
     HDF5::File file(filename.c_str());
@@ -101,7 +101,7 @@ template <class Vector>
 bool checkAppendSequence(Vector const &written0, Vector const &written1) {
   bool passed = true;
   using ft = typename Vector::block_type::field_type;
-  std::string const filename("out-sequence.h5");
+  std::string const filename("out-sequence-append.h5");
   {
     deleteIfNecessary(filename);
     HDF5::File file(filename.c_str());