diff --git a/internal/ceres/block_random_access_crs_matrix_test.cc b/internal/ceres/block_random_access_crs_matrix_test.cc
new file mode 100644
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+++ b/internal/ceres/block_random_access_crs_matrix_test.cc
@@ -0,0 +1,148 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2013 Google Inc. All rights reserved.
+// http://code.google.com/p/ceres-solver/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice,
+//   this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors may be
+//   used to endorse or promote products derived from this software without
+//   specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// Author: sameeragarwal@google.com (Sameer Agarwal)
+
+#include <limits>
+#include <vector>
+#include "ceres/block_random_access_crs_matrix.h"
+#include "ceres/internal/eigen.h"
+#include "glog/logging.h"
+#include "gtest/gtest.h"
+
+namespace ceres {
+namespace internal {
+
+TEST(BlockRandomAccessCRSMatrix, GetCell) {
+  vector<int> blocks;
+  blocks.push_back(3);
+  blocks.push_back(4);
+  blocks.push_back(5);
+  const int num_rows = 3 + 4 + 5;
+
+  set< pair<int, int> > block_pairs;
+  int num_nonzeros = 0;
+  block_pairs.insert(make_pair(0, 0));
+  num_nonzeros += blocks[0] * blocks[0];
+
+  block_pairs.insert(make_pair(1, 1));
+  num_nonzeros += blocks[1] * blocks[1];
+
+  block_pairs.insert(make_pair(1, 2));
+  num_nonzeros += blocks[1] * blocks[2];
+
+  block_pairs.insert(make_pair(2, 0));
+  num_nonzeros += blocks[2] * blocks[0];
+
+  BlockRandomAccessCRSMatrix m(blocks, block_pairs);
+  EXPECT_EQ(m.num_rows(), num_rows);
+  EXPECT_EQ(m.num_cols(), num_rows);
+
+  for (set<pair<int, int> >::const_iterator it = block_pairs.begin();
+       it != block_pairs.end();
+       ++it) {
+    const int row_block_id = it->first;
+    const int col_block_id = it->second;
+    int row;
+    int col;
+    int row_stride;
+    int col_stride;
+    CellInfo* cell =  m.GetCell(row_block_id, col_block_id,
+                                &row, &col,
+                                &row_stride, &col_stride);
+    EXPECT_TRUE(cell != NULL);
+    EXPECT_EQ(row, 0);
+    EXPECT_EQ(col, 0);
+
+    // Write into the block.
+    MatrixRef(cell->values, row_stride, col_stride).block(
+        row, col, blocks[row_block_id], blocks[col_block_id]) =
+        (row_block_id + 1) * (col_block_id +1) *
+        Matrix::Ones(blocks[row_block_id], blocks[col_block_id]);
+  }
+
+  const CompressedRowSparseMatrix* crsm = m.matrix();
+  EXPECT_EQ(crsm->num_nonzeros(), num_nonzeros);
+
+  Matrix dense;
+  crsm->ToDenseMatrix(&dense);
+
+  double kTolerance = 1e-14;
+
+  // (0,0)
+  EXPECT_NEAR((dense.block(0, 0, 3, 3) - Matrix::Ones(3, 3)).norm(),
+              0.0,
+              kTolerance);
+  // (1,1)
+  EXPECT_NEAR((dense.block(3, 3, 4, 4) - 2 * 2 * Matrix::Ones(4, 4)).norm(),
+              0.0,
+              kTolerance);
+  // (1,2)
+  EXPECT_NEAR((dense.block(3, 3 + 4, 4, 5) - 2 * 3 * Matrix::Ones(4, 5)).norm(),
+              0.0,
+              kTolerance);
+  // (2,0)
+  EXPECT_NEAR((dense.block(3 + 4, 0, 5, 3) - 3 * 1 * Matrix::Ones(5, 3)).norm(),
+              0.0,
+              kTolerance);
+
+  // There is nothing else in the matrix besides these four blocks.
+  EXPECT_NEAR(dense.norm(), sqrt(9. + 16. * 16. + 36. * 20. + 9. * 15.),
+              kTolerance);
+}
+
+// IntPairToLong is private, thus this fixture is needed to access and
+// test it.
+class BlockRandomAccessCRSMatrixTest : public ::testing::Test {
+ public:
+  virtual void SetUp() {
+    vector<int> blocks;
+    blocks.push_back(1);
+    set< pair<int, int> > block_pairs;
+    block_pairs.insert(make_pair(0, 0));
+    m_.reset(new BlockRandomAccessCRSMatrix(blocks, block_pairs));
+  }
+
+  void CheckIntPair(int a, int b) {
+    int64 value = m_->IntPairToLong(a, b);
+    EXPECT_GT(value, 0) << "Overflow a = " << a << " b = " << b;
+    EXPECT_GT(value, a) << "Overflow a = " << a << " b = " << b;
+    EXPECT_GT(value, b) << "Overflow a = " << a << " b = " << b;
+  }
+
+ private:
+  scoped_ptr<BlockRandomAccessCRSMatrix> m_;
+};
+
+TEST_F(BlockRandomAccessCRSMatrixTest, IntPairToLongOverflow) {
+  CheckIntPair(numeric_limits<int>::max(), numeric_limits<int>::max());
+}
+
+
+}  // namespace internal
+}  // namespace ceres