diff --git a/internal/ceres/test_util.h b/internal/ceres/test_util.h
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+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2015 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// 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: keir@google.com (Keir Mierle)
+
+#ifndef CERES_INTERNAL_TEST_UTIL_H_
+#define CERES_INTERNAL_TEST_UTIL_H_
+
+#include <string>
+#include "ceres/internal/port.h"
+#include "ceres/problem.h"
+#include "ceres/solver.h"
+#include "ceres/stringprintf.h"
+#include "gtest/gtest.h"
+
+namespace ceres {
+namespace internal {
+
+// Expects that x and y have a relative difference of no more than
+// max_abs_relative_difference. If either x or y is zero, then the relative
+// difference is interpreted as an absolute difference.
+bool ExpectClose(double x, double y, double max_abs_relative_difference);
+
+// Expects that for all i = 1,.., n - 1
+//
+//   |p[i] - q[i]| / max(|p[i]|, |q[i]|) < tolerance
+void ExpectArraysClose(int n,
+                       const double* p,
+                       const double* q,
+                       double tolerance);
+
+// Expects that for all i = 1,.., n - 1
+//
+//   |p[i] / max_norm_p - q[i] / max_norm_q| < tolerance
+//
+// where max_norm_p and max_norm_q are the max norms of the arrays p
+// and q respectively.
+void ExpectArraysCloseUptoScale(int n,
+                                const double* p,
+                                const double* q,
+                                double tolerance);
+
+// Construct a fully qualified path for the test file depending on the
+// local build/testing environment.
+std::string TestFileAbsolutePath(const std::string& filename);
+
+std::string ToString(const Solver::Options& options);
+
+// A templated test fixture, that is used for testing Ceres end to end
+// by computing a solution to the problem for a given solver
+// configuration and comparing it to a reference solver configuration.
+//
+// It is assumed that the SystemTestProblem has an Solver::Options
+// struct that contains the reference Solver configuration.
+template <typename SystemTestProblem>
+class SystemTest : public ::testing::Test {
+ protected:
+  virtual void SetUp() {
+    SystemTestProblem system_test_problem;
+    SolveAndEvaluateFinalResiduals(
+        *system_test_problem.mutable_solver_options(),
+        system_test_problem.mutable_problem(),
+        &expected_final_residuals_);
+  }
+
+  void RunSolverForConfigAndExpectResidualsMatch(const Solver::Options& options,
+                                                 Problem* problem) {
+    std::vector<double> final_residuals;
+    SolveAndEvaluateFinalResiduals(options, problem, &final_residuals);
+
+    // We compare solutions by comparing their residual vectors. We do
+    // not compare parameter vectors because it is much more brittle
+    // and error prone to do so, since the same problem can have
+    // nearly the same residuals at two completely different positions
+    // in parameter space.
+    CHECK_EQ(expected_final_residuals_.size(), final_residuals.size());
+    for (int i = 0; i < final_residuals.size(); ++i) {
+      EXPECT_NEAR(final_residuals[i],
+                  expected_final_residuals_[i],
+                  SystemTestProblem::kResidualTolerance)
+          << "Not close enough residual:" << i;
+    }
+  }
+
+  void SolveAndEvaluateFinalResiduals(const Solver::Options& options,
+                                      Problem* problem,
+                                      std::vector<double>* final_residuals) {
+    Solver::Summary summary;
+    Solve(options, problem, &summary);
+    CHECK_NE(summary.termination_type, ceres::FAILURE);
+    problem->Evaluate(Problem::EvaluateOptions(),
+                      nullptr,
+                      final_residuals,
+                      nullptr,
+                      nullptr);
+  }
+
+  std::vector<double> expected_final_residuals_;
+};
+
+}  // namespace internal
+}  // namespace ceres
+
+#endif  // CERES_INTERNAL_TEST_UTIL_H_