diff --git a/gtsam/hybrid/tests/testHybridEstimation.cpp b/gtsam/hybrid/tests/testHybridEstimation.cpp
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+/* ----------------------------------------------------------------------------
+
+ * GTSAM Copyright 2010, Georgia Tech Research Corporation,
+ * Atlanta, Georgia 30332-0415
+ * All Rights Reserved
+ * Authors: Frank Dellaert, et al. (see THANKS for the full author list)
+
+ * See LICENSE for the license information
+
+ * -------------------------------------------------------------------------- */
+
+/**
+ * @file    testHybridEstimation.cpp
+ * @brief   Unit tests for end-to-end Hybrid Estimation
+ * @author  Varun Agrawal
+ */
+
+#include <gtsam/geometry/Pose2.h>
+#include <gtsam/hybrid/HybridBayesNet.h>
+#include <gtsam/hybrid/HybridNonlinearFactorGraph.h>
+#include <gtsam/hybrid/HybridNonlinearISAM.h>
+#include <gtsam/hybrid/HybridSmoother.h>
+#include <gtsam/hybrid/MixtureFactor.h>
+#include <gtsam/inference/Symbol.h>
+#include <gtsam/linear/GaussianBayesNet.h>
+#include <gtsam/linear/GaussianFactorGraph.h>
+#include <gtsam/linear/JacobianFactor.h>
+#include <gtsam/linear/NoiseModel.h>
+#include <gtsam/nonlinear/NonlinearFactorGraph.h>
+#include <gtsam/nonlinear/PriorFactor.h>
+#include <gtsam/slam/BetweenFactor.h>
+
+// Include for test suite
+#include <CppUnitLite/TestHarness.h>
+
+#include "Switching.h"
+
+using namespace std;
+using namespace gtsam;
+
+using symbol_shorthand::X;
+
+Ordering getOrdering(HybridGaussianFactorGraph& factors,
+                     const HybridGaussianFactorGraph& newFactors) {
+  factors += newFactors;
+  // Get all the discrete keys from the factors
+  KeySet allDiscrete = factors.discreteKeys();
+
+  // Create KeyVector with continuous keys followed by discrete keys.
+  KeyVector newKeysDiscreteLast;
+  const KeySet newFactorKeys = newFactors.keys();
+  // Insert continuous keys first.
+  for (auto& k : newFactorKeys) {
+    if (!allDiscrete.exists(k)) {
+      newKeysDiscreteLast.push_back(k);
+    }
+  }
+
+  // Insert discrete keys at the end
+  std::copy(allDiscrete.begin(), allDiscrete.end(),
+            std::back_inserter(newKeysDiscreteLast));
+
+  const VariableIndex index(factors);
+
+  // Get an ordering where the new keys are eliminated last
+  Ordering ordering = Ordering::ColamdConstrainedLast(
+      index, KeyVector(newKeysDiscreteLast.begin(), newKeysDiscreteLast.end()),
+      true);
+  return ordering;
+}
+
+/****************************************************************************/
+// Test approximate inference with an additional pruning step.
+TEST(HybridNonlinearISAM, Incremental) {
+  size_t K = 10;
+  std::vector<double> measurements = {0, 1, 2, 2, 2, 2, 3, 4, 5, 6, 6};
+  // Ground truth discrete seq
+  std::vector<size_t> discrete_seq = {1, 1, 0, 0, 0, 1, 1, 1, 1, 0};
+  Switching switching(K, 1.0, 0.1, measurements);
+  // HybridNonlinearISAM smoother;
+  HybridSmoother smoother;
+  HybridNonlinearFactorGraph graph;
+  Values initial;
+
+  // switching.nonlinearFactorGraph.print();
+  // switching.linearizationPoint.print();
+  // Add the X(1) prior
+  graph.push_back(switching.nonlinearFactorGraph.at(0));
+  initial.insert(X(1), switching.linearizationPoint.at<double>(X(1)));
+
+  HybridGaussianFactorGraph linearized;
+  HybridGaussianFactorGraph bayesNet;
+
+  for (size_t k = 1; k < K; k++) {
+    // Motion Model
+    graph.push_back(switching.nonlinearFactorGraph.at(k));
+    // Measurement
+    graph.push_back(switching.nonlinearFactorGraph.at(k + K - 1));
+
+    initial.insert(X(k + 1), switching.linearizationPoint.at<double>(X(k + 1)));
+
+    // std::cout << "\n=============  " << k << std::endl;
+    // graph.print();
+
+    bayesNet = smoother.hybridBayesNet();
+    linearized = *graph.linearize(initial);
+    Ordering ordering = getOrdering(bayesNet, linearized);
+
+    ordering.print();
+    smoother.update(linearized, ordering, 3);
+    // if (k == 2) exit(0);
+    // smoother.hybridBayesNet().print();
+    graph.resize(0);
+    // initial.clear();
+  }
+}
+
+/* ************************************************************************* */
+int main() {
+  TestResult tr;
+  return TestRegistry::runAllTests(tr);
+}
+/* ************************************************************************* */