diff --git a/gtsam/hybrid/tests/testHybridGaussianConditional.cpp b/gtsam/hybrid/tests/testHybridGaussianConditional.cpp
index 8bb83cac4..7c7fc3ea5 100644
--- a/gtsam/hybrid/tests/testHybridGaussianConditional.cpp
+++ b/gtsam/hybrid/tests/testHybridGaussianConditional.cpp
@@ -238,22 +238,27 @@ TEST(HybridGaussianConditional, Likelihood2) {
   EXPECT_DOUBLES_EQUAL(ratio[0], ratio[1], 1e-8);
 }
 
+/* ************************************************************************* */
+namespace two_mode_measurement {
+// Create a two key conditional:
+const DiscreteKeys modes{{M(1), 2}, {M(2), 2}};
+const std::vector<GaussianConditional::shared_ptr> gcs = {
+    GaussianConditional::sharedMeanAndStddev(Z(0), Vector1(1), 1),
+    GaussianConditional::sharedMeanAndStddev(Z(0), Vector1(2), 2),
+    GaussianConditional::sharedMeanAndStddev(Z(0), Vector1(3), 3),
+    GaussianConditional::sharedMeanAndStddev(Z(0), Vector1(4), 4)};
+const HybridGaussianConditional::Conditionals conditionals(modes, gcs);
+const auto hgc =
+    std::make_shared<HybridGaussianConditional>(modes, conditionals);
+}  // namespace two_mode_measurement
+
 /* ************************************************************************* */
 // Test pruning a HybridGaussianConditional with two discrete keys, based on a
 // DecisionTreeFactor with 3 keys:
 TEST(HybridGaussianConditional, Prune) {
-  // Create a two key conditional:
-  DiscreteKeys modes{{M(1), 2}, {M(2), 2}};
-  std::vector<GaussianConditional::shared_ptr> gcs;
-  for (size_t i = 0; i < 4; i++) {
-    gcs.push_back(
-        GaussianConditional::sharedMeanAndStddev(Z(0), Vector1(i + 1), i + 1));
-  }
-  auto empty = std::make_shared<GaussianConditional>();
-  HybridGaussianConditional::Conditionals conditionals(modes, gcs);
-  HybridGaussianConditional hgc(modes, conditionals);
+  using two_mode_measurement::hgc;
 
-  DiscreteKeys keys = modes;
+  DiscreteKeys keys = two_mode_measurement::modes;
   keys.push_back({M(3), 2});
   {
     for (size_t i = 0; i < 8; i++) {
@@ -262,7 +267,7 @@ TEST(HybridGaussianConditional, Prune) {
       const DecisionTreeFactor decisionTreeFactor(keys, potentials);
       // Prune the HybridGaussianConditional
       const auto pruned =
-          hgc.prune(DiscreteConditional(keys.size(), decisionTreeFactor));
+          hgc->prune(DiscreteConditional(keys.size(), decisionTreeFactor));
       // Check that the pruned HybridGaussianConditional has 1 conditional
       EXPECT_LONGS_EQUAL(1, pruned->nrComponents());
     }
@@ -273,14 +278,14 @@ TEST(HybridGaussianConditional, Prune) {
     const DecisionTreeFactor decisionTreeFactor(keys, potentials);
 
     const auto pruned =
-        hgc.prune(DiscreteConditional(keys.size(), decisionTreeFactor));
+        hgc->prune(DiscreteConditional(keys.size(), decisionTreeFactor));
 
     // Check that the pruned HybridGaussianConditional has 2 conditionals
     EXPECT_LONGS_EQUAL(2, pruned->nrComponents());
 
     // Check that the minimum negLogConstant is set correctly
     EXPECT_DOUBLES_EQUAL(
-        hgc.conditionals()({{M(1), 0}, {M(2), 1}})->negLogConstant(),
+        hgc->conditionals()({{M(1), 0}, {M(2), 1}})->negLogConstant(),
         pruned->negLogConstant(), 1e-9);
   }
   {
@@ -289,18 +294,74 @@ TEST(HybridGaussianConditional, Prune) {
     const DecisionTreeFactor decisionTreeFactor(keys, potentials);
 
     const auto pruned =
-        hgc.prune(DiscreteConditional(keys.size(), decisionTreeFactor));
+        hgc->prune(DiscreteConditional(keys.size(), decisionTreeFactor));
 
     // Check that the pruned HybridGaussianConditional has 3 conditionals
     EXPECT_LONGS_EQUAL(3, pruned->nrComponents());
 
     // Check that the minimum negLogConstant is correct
-    EXPECT_DOUBLES_EQUAL(hgc.negLogConstant(), pruned->negLogConstant(), 1e-9);
+    EXPECT_DOUBLES_EQUAL(hgc->negLogConstant(), pruned->negLogConstant(), 1e-9);
   }
 }
 
-/* *************************************************************************
+/* ************************************************************************* */
+
+#include <gtsam/hybrid/HybridConditional.h>
+
+/**
+ * Return a HybridConditional by choosing branches based on the given discrete
+ * values. If all discrete parents are specified, return a HybridConditional
+ * which is just a GaussianConditional.
  */
+HybridConditional::shared_ptr choose(
+    const HybridGaussianConditional::shared_ptr &self,
+    const DiscreteValues &discreteValues) {
+  const auto &discreteParents = self->discreteKeys();
+  DiscreteValues deadParentValues;
+  DiscreteKeys liveParents;
+  for (const auto &key : discreteParents) {
+    auto it = discreteValues.find(key.first);
+    if (it != discreteValues.end())
+      deadParentValues[key.first] = it->second;
+    else
+      liveParents.emplace_back(key);
+  }
+  // If so then we just get the corresponding Gaussian conditional:
+  if (deadParentValues.size() == discreteParents.size()) {
+    // print on how many discreteParents we are choosing:
+    return std::make_shared<HybridConditional>(self->choose(deadParentValues));
+  } else if (liveParents.size() > 0) {
+    auto newTree = self->factors();
+    for (auto &&[key, value] : discreteValues) {
+      newTree = newTree.choose(key, value);
+    }
+    return std::make_shared<HybridConditional>(
+        std::make_shared<HybridGaussianConditional>(liveParents, newTree));
+  } else {
+    // Add as-is
+    return std::make_shared<HybridConditional>(self);
+  }
+}
+
+/* ************************************************************************* */
+// Test the pruning and dead-mode removal.
+TEST(HybridGaussianConditional, PrunePlus) {
+  using two_mode_measurement::hgc;  // two discrete parents
+
+  const HybridConditional::shared_ptr same = choose(hgc, {});
+  EXPECT(same->isHybrid());
+  EXPECT(same->asHybrid()->nrComponents() == 4);
+
+  const HybridConditional::shared_ptr oneParent = choose(hgc, {{M(1), 0}});
+  EXPECT(oneParent->isHybrid());
+  EXPECT(oneParent->asHybrid()->nrComponents() == 2);
+
+  const HybridConditional::shared_ptr gaussian =
+      choose(hgc, {{M(1), 0}, {M(2), 1}});
+  EXPECT(gaussian->asGaussian());
+}
+
+/* ************************************************************************* */
 int main() {
   TestResult tr;
   return TestRegistry::runAllTests(tr);