Fix a bunch of annoying compiler warnings in tests
diff --git a/test/adjoint.cpp b/test/adjoint.cpp
index 210a4d9..37d23b1 100644
--- a/test/adjoint.cpp
+++ b/test/adjoint.cpp
@@ -63,10 +63,10 @@
 };
 
 template<typename MatrixType, typename Scalar = typename MatrixType::Scalar>
-MatrixType RandomMatrix(int rows, int cols, Scalar min, Scalar max) {
+MatrixType RandomMatrix(Index rows, Index cols, Scalar min, Scalar max) {
   MatrixType M = MatrixType(rows, cols);
-  for (int i=0; i<rows; ++i) {
-    for (int j=0; j<cols; ++j) {
+  for (Index i=0; i<rows; ++i) {
+    for (Index j=0; j<cols; ++j) {
       M(i, j) = Eigen::internal::random<Scalar>(min, max);
     }
   }