// This macro opens and inverts 20 images,
// verifying that the image was actually inverted. 
// ImageJ 1.31c fixes a synchronization bug that
// caused this macro to sometimes fail on Mac OS X. 
  n = 20;
  for (i=1; i<=n; i++) {
      run("New...", "name="+i+" type=8-bit fill=White width=100 height=100");
      run("Invert");
      if (getPixel(0,0)!=0)
          print("Synchronization error: "+i);
 }
  for (i=n; i>=1; i--) {
       selectWindow(""+i);
      run("Close");
 }