diff --git a/test/unit/eigensolver/test_tridiag_solver_merge.cpp b/test/unit/eigensolver/test_tridiag_solver_merge.cpp
index 468f184ad1..543bad1285 100644
--- a/test/unit/eigensolver/test_tridiag_solver_merge.cpp
+++ b/test/unit/eigensolver/test_tridiag_solver_merge.cpp
@@ -82,7 +82,7 @@ TYPED_TEST(TridiagEigensolverMergeTest, SortIndex) {
 }
 
 TEST(StablePartitionIndexOnDeflated, FullRange) {
-  const SizeType n = 10;
+  constexpr SizeType n = 10;
   const SizeType nb = 3;
 
   const LocalElementSize sz(n, 1);
@@ -93,32 +93,62 @@ TEST(StablePartitionIndexOnDeflated, FullRange) {
   Matrix<SizeType, Device::CPU> in(sz, bk);
   Matrix<SizeType, Device::CPU> out(sz, bk);
 
-  std::vector<ColType> c_arr{ColType::LowerHalf, ColType::Dense,     ColType::Deflated,
-                             ColType::Deflated,  ColType::UpperHalf, ColType::UpperHalf,
-                             ColType::LowerHalf, ColType::Dense,     ColType::Deflated,
-                             ColType::LowerHalf};
+  // Note:
+  // UpperHalf  -> u
+  // Dense      -> f
+  // LowerHalf  -> l
+  // Deflated   -> d
+
+  // | 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| initial
+  // | l| f|d1|d2| u| u| l| f|d3| l| c_arr
+  std::array<ColType, n> c_arr{ColType::LowerHalf, ColType::Dense,
+                               ColType::Deflated,  ColType::Deflated,
+                               ColType::UpperHalf, ColType::UpperHal ColType::LowerHalf,
+                               ColType::Dense,     ColType::Deflate ColType::LowerHalf};
   DLAF_ASSERT(c_arr.size() == to_sizet(n), n);
   dlaf::matrix::util::set(c, [&c_arr](GlobalElementIndex i) { return c_arr[to_sizet(i.row())]; });
 
-  // f, u, d, d, l, u, l, f, d, l
-  std::vector<double> vals_arr{1, 4, 2, 3, 0, 5, 6, 7, 8, 9};
-  std::vector<SizeType> in_arr{1, 4, 2, 3, 0, 5, 6, 7, 8, 9};
+  // | 1| 4| 2| 3| 0| 5| 6| 7| 8| 9| in_arr
+  // | f| u|d1|d2| l| u| l| f|d3| l| c_arr permuted by in_arr
+  std::array<SizeType, n> in_arr{1, 4, 2, 3, 0, 5, 6, 7, 8, 9};
+  dlaf::matrix::util::set(in, [&in_arr](GlobalElementIndex i) { return in_arr[to_sizet(i.row())]; });
+
+  // | 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| initial
+  // |30|10| 2| 3|20|40|50|60| 1|70| vals_arr
+  //
+  // | 1| 4| 2| 3| 0| 5| 6| 7| 8| 9| in_arr
+  // | f| u|d1|d2| l| u| l| f|d3| l| c_arr permuted by in_arr
+  // |10|20| 2| 3|30|40|50|60| 1|70| vals_arr permuted by in_arr
+  std::array<double, n> vals_arr{30, 10, 2, 3, 20, 40, 50, 60, 1, 70};
   dlaf::matrix::util::set(vals,
                           [&vals_arr](GlobalElementIndex i) { return vals_arr[to_sizet(i.row())]; });
-  dlaf::matrix::util::set(in, [&in_arr](GlobalElementIndex i) { return in_arr[to_sizet(i.row())]; });
 
   const SizeType i_begin = 0;
   const SizeType i_end = 4;
   auto k = stablePartitionIndexForDeflation(i_begin, i_end, c, vals, in, out);
 
-  ASSERT_TRUE(tt::sync_wait(std::move(k)) == 7);
+  // | 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| initial
+  // | l| f|d1|d2| u| u| l| f|d3| l| c_arr
+  // |30|10| 2| 3|20|40|50|60| 1|70| vals_arr
+  //
+  // | 1| 4| 0| 5| 6| 7| 9| 8| 2| 3| out_arr
+  // | f| u| l| u| l| f| l|d3|d1|d2| c_arr permuted by out_arr
+  // |10|20|30|40|50|60|70| 1| 2| 3| vals_arr permuted by out_arr
+
+  const SizeType k_value = tt::sync_wait(std::move(k));
+  ASSERT_TRUE(k_value == 7);
 
-  // f u l u l f l d d d
-  std::vector<SizeType> expected_out_arr{1, 4, 0, 5, 6, 7, 9, 2, 3, 8};
+  std::array<SizeType, n> expected_out_arr{1, 4, 0, 5, 6, 7, 9, 8, 2, 3};
   auto expected_out = [&expected_out_arr](GlobalElementIndex i) {
     return expected_out_arr[to_sizet(i.row())];
   };
   CHECK_MATRIX_EQ(expected_out, out);
+
+  const SizeType* out_ptr = tt::sync_wait(out.read(LocalTileIndex(0, 0))).get().ptr();
+  EXPECT_TRUE(std::is_sorted(out_ptr + k_value, out_ptr + n,
+                             [&vals_arr](const SizeType i, const SizeType j) {
+                               return vals_arr[to_sizet(i)] < vals_arr[tosizet(j)];
+                             }));
 }
 
 TYPED_TEST(TridiagEigensolverMergeTest, Deflation) {