diff --git a/tests/core/Test_reunitarise.cc b/tests/core/Test_reunitarise.cc
new file mode 100644
index 00000000..3e78b961
--- /dev/null
+++ b/tests/core/Test_reunitarise.cc
@@ -0,0 +1,137 @@
+    /*************************************************************************************
+
+    Grid physics library, www.github.com/paboyle/Grid 
+
+    Source file: ./tests/Test_quenched_update.cc
+
+    Copyright (C) 2015
+
+Author: Azusa Yamaguchi <ayamaguc@staffmail.ed.ac.uk>
+Author: Peter Boyle <paboyle@ph.ed.ac.uk>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+    See the full license in the file "LICENSE" in the top level distribution directory
+    *************************************************************************************/
+    /*  END LEGAL */
+#include <Grid/Grid.h>
+
+using namespace std;
+using namespace Grid;
+ ;
+
+int main (int argc, char ** argv)
+{
+  Grid_init(&argc,&argv);
+
+  std::vector<int> latt({8,8,8,8});
+  GridCartesian * grid = SpaceTimeGrid::makeFourDimGrid(latt, 
+							GridDefaultSimd(Nd,vComplexD::Nsimd()),
+							GridDefaultMpi());
+
+  GridCartesian * gridF = SpaceTimeGrid::makeFourDimGrid(latt, 
+							GridDefaultSimd(Nd,vComplexF::Nsimd()),
+							GridDefaultMpi());
+  
+
+  ///////////////////////////////
+  // Configuration of known size
+  ///////////////////////////////
+  LatticeColourMatrixD ident(grid);
+  LatticeColourMatrixD U(grid);
+  LatticeColourMatrixD UU(grid);
+  LatticeColourMatrixD tmp(grid);
+  LatticeColourMatrixD org(grid);
+  LatticeColourMatrixF UF(gridF);
+
+  LatticeGaugeField Umu(grid);
+
+  ident =1.0;
+
+  // RNG set up for test
+  std::vector<int> pseeds({1,2,3,4,5}); // once I caught a fish alive
+  std::vector<int> sseeds({6,7,8,9,10});// then i let it go again
+  GridParallelRNG  pRNG(grid); pRNG.SeedFixedIntegers(pseeds);
+  GridSerialRNG    sRNG;       sRNG.SeedFixedIntegers(sseeds);
+
+  SU<Nc>::HotConfiguration(pRNG,Umu);
+
+  U = PeekIndex<LorentzIndex>(Umu,0);
+  org=U;
+
+
+  tmp=  U*adj(U) - ident ;
+  RealD Def1 = norm2( tmp );
+  std::cout << " Defect1 "<<Def1<<std::endl;
+
+  tmp = U - org;
+  std::cout << "Diff1 "<<norm2(tmp)<<std::endl;
+  precisionChange(UF,U);
+  precisionChange(U,UF);
+
+  tmp=  U*adj(U) - ident ;
+  RealD Def2 = norm2(  tmp );
+  std::cout << " Defect2 "<<Def2<<std::endl;
+
+  tmp = U - org;
+  std::cout << "Diff2 "<<norm2(tmp)<<std::endl;
+
+  U = ProjectOnGroup(U);
+
+  tmp=  U*adj(U) - ident ;
+  RealD Def3 = norm2(  tmp);
+  std::cout << " Defect3 "<<Def3<<std::endl;
+
+
+  tmp = U - org;
+  std::cout << "Diff3 "<<norm2(tmp)<<std::endl;
+
+  LatticeComplexD detU(grid);
+  LatticeComplexD detUU(grid);
+
+  detU= Determinant(U) ;
+  std::cout << "Determinant before screw up " <<detU<<std::endl;
+
+  std::cout << " Screwing up determinant " << std::endl;
+
+  RealD theta = 0.2;
+  ComplexD phase(cos(theta),sin(theta));
+  for(int i=0;i<Nc;i++){
+    auto element = PeekIndex<ColourIndex>(U,Nc-1,i);
+    element = element * phase;
+    PokeIndex<ColourIndex>(U,element,Nc-1,i);
+  }  
+  UU=U;
+
+  detU= Determinant(U) ;
+  std::cout << "Determinant after screw up " <<detU<<std::endl;
+
+  ProjectSU3(U);
+  detU= Determinant(U) ;
+  std::cout << "Determinant ProjectSU3  " <<detU<<std::endl;
+  detU= detU -1.0;
+  std::cout << "Determinant ProjectSU3 defect " <<norm2(detU)<<std::endl;
+
+  ProjectSUn<3>(UU);
+  detUU= Determinant(UU);
+  std::cout << "Determinant ProjectSUn " <<detUU<<std::endl;
+  std::cout << "Determinant ProjectSUn defect " <<norm2(detUU)<<std::endl;
+  
+  Grid_finalize();
+}
+
+
+
+