diff --git a/tests/metropolis_hasting_producer_12.cc b/tests/metropolis_hasting_producer_12.cc
new file mode 100644
index 00000000..6b7511aa
--- /dev/null
+++ b/tests/metropolis_hasting_producer_12.cc
@@ -0,0 +1,97 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2020 by the SampleFlow authors.
+//
+// This file is part of the SampleFlow library.
+//
+// The SampleFlow library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of SampleFlow.
+//
+// ---------------------------------------------------------------------
+
+
+// Test the Metropolis-Hastings producer with a diagonally elongated
+// distribution.
+
+#include <iostream>
+#include <sampleflow/producers/metropolis_hastings.h>
+#include <sampleflow/filters/conversion.h>
+#include <sampleflow/consumers/covariance_matrix.h>
+#include <sampleflow/consumers/mean_value.h>
+#include <sampleflow/consumers/stream_output.h>
+#include <valarray>
+#include <random>
+#include <cmath>
+
+
+using SampleType = std::valarray<double>;
+
+
+double log_likelihood (const SampleType &x)
+{
+  double mu[2] = {0, 0};
+  // double cov[2][2] = {{10, 0}, {0, 1}};
+  double cov_inv[2][2] = {{1.0/10.0, 0},{0, 1}};
+
+  double phi = 3.1415 / 6;
+  double rotation_matrix[2][2] = {{cos(phi), sin(phi)},
+    {-sin(phi), cos(phi)}
+  };
+  double rotation_matrix_transpose[2][2] = {{cos(phi), -sin(phi)},
+    {sin(phi), cos(phi)}
+  };
+  double RC[2][2] = {{
+      rotation_matrix[0][0] *cov_inv[0][0] + rotation_matrix[0][1] *cov_inv[1][0],
+      rotation_matrix[0][0] *cov_inv[0][1] + rotation_matrix[0][1] *cov_inv[1][1]
+    },
+    {
+      rotation_matrix[1][0] *cov_inv[0][0] + rotation_matrix[1][1] *cov_inv[1][0],
+      rotation_matrix[1][0] *cov_inv[0][1] + rotation_matrix[1][1] *cov_inv[1][1]
+    }
+  };
+  double rotated_cov_inv[2][2] = {{
+      RC[0][0] *rotation_matrix_transpose[0][0] + RC[0][1] *rotation_matrix_transpose[1][0],
+      RC[0][0] *rotation_matrix_transpose[0][1] + RC[0][1] *rotation_matrix_transpose[1][1]
+    },
+    {
+      RC[1][0] *rotation_matrix_transpose[0][0] + RC[1][1] *rotation_matrix_transpose[1][0],
+      RC[1][0] *rotation_matrix_transpose[0][1] + RC[1][1] *rotation_matrix_transpose[1][1]
+    }
+  };
+
+  double dev[2] = {x[0] - mu[0], x[1] - mu[1]};
+  double dev_covinv[2] = {dev[0] *rotated_cov_inv[0][0] + dev[1] *rotated_cov_inv[0][1],
+                          dev[0] *rotated_cov_inv[1][0] + dev[1] *rotated_cov_inv[1][1]
+                         };
+  double dev_covinv_dev = dev_covinv[0] * dev[0] + dev_covinv[1] * dev[1];
+  return -0.5 * dev_covinv_dev;
+}
+
+
+std::pair<SampleType,double> perturb (const SampleType &x)
+{
+  static std::mt19937 rng;
+  std::normal_distribution<double> distribution(0, 1);
+  SampleType y = x;
+  for (auto &el : y)
+    el += distribution(rng);
+  return {y, 1.0};
+}
+
+
+int main ()
+{
+  SampleFlow::Producers::MetropolisHastings<SampleType> mh_sampler;
+  SampleFlow::Consumers::CovarianceMatrix<SampleType> cov_matrix;
+  SampleFlow::Consumers::MeanValue<SampleType> mean_value;
+  cov_matrix.connect_to_producer(mh_sampler);
+  mean_value.connect_to_producer(mh_sampler);
+  // Sample, starting at an asymmetric point, and creating 100,000 samples
+  mh_sampler.sample({5, -1}, &log_likelihood, &perturb, 100000);
+  std::cout << "Mean value = " << mean_value.get()[0] << std::endl;
+  std::cout << "Mean value = " << mean_value.get()[1] << std::endl;
+}
diff --git a/tests/metropolis_hasting_producer_12.output b/tests/metropolis_hasting_producer_12.output
new file mode 100644
index 00000000..09b305f7
--- /dev/null
+++ b/tests/metropolis_hasting_producer_12.output
@@ -0,0 +1,2 @@
+Mean value = 0.0482154
+Mean value = -0.0384958
diff --git a/tests/metropolis_hasting_producer_13.cc b/tests/metropolis_hasting_producer_13.cc
new file mode 100644
index 00000000..c45153fc
--- /dev/null
+++ b/tests/metropolis_hasting_producer_13.cc
@@ -0,0 +1,138 @@
+// ---------------------------------------------------------------------
+//
+// Copyright (C) 2020 by the SampleFlow authors.
+//
+// This file is part of the SampleFlow library.
+//
+// The SampleFlow library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of SampleFlow.
+//
+// ---------------------------------------------------------------------
+
+
+// Copy of metropolis_hasting_producer_12, but with adaptive sampling.
+// Test the Metropolis-Hastings producer with a diagonally elongated
+// distribution.
+
+#include <iostream>
+#include <sampleflow/producers/metropolis_hastings.h>
+#include <sampleflow/filters/conversion.h>
+#include <sampleflow/consumers/covariance_matrix.h>
+#include <sampleflow/consumers/mean_value.h>
+#include <valarray>
+#include <random>
+#include <cmath>
+
+
+using SampleType = std::valarray<double>;
+using MatrixType = boost::numeric::ublas::matrix<double>;
+using VectorType = boost::numeric::ublas::vector<double>;
+
+
+double log_likelihood (const SampleType &x)
+{
+  double mu[2] = {0, 0};
+  // double cov[2][2] = {{10, 0}, {0, 1}};
+  double cov_inv[2][2] = {{1.0/10.0, 0},{0, 1}};
+
+  double phi = 3.1415 / 6;
+  double rotation_matrix[2][2] = {{cos(phi), sin(phi)},
+    {-sin(phi), cos(phi)}
+  };
+  double rotation_matrix_transpose[2][2] = {{cos(phi), -sin(phi)},
+    {sin(phi), cos(phi)}
+  };
+  double RC[2][2] = {{
+      rotation_matrix[0][0] *cov_inv[0][0] + rotation_matrix[0][1] *cov_inv[1][0],
+      rotation_matrix[0][0] *cov_inv[0][1] + rotation_matrix[0][1] *cov_inv[1][1]
+    },
+    {
+      rotation_matrix[1][0] *cov_inv[0][0] + rotation_matrix[1][1] *cov_inv[1][0],
+      rotation_matrix[1][0] *cov_inv[0][1] + rotation_matrix[1][1] *cov_inv[1][1]
+    }
+  };
+  double rotated_cov_inv[2][2] = {{
+      RC[0][0] *rotation_matrix_transpose[0][0] + RC[0][1] *rotation_matrix_transpose[1][0],
+      RC[0][0] *rotation_matrix_transpose[0][1] + RC[0][1] *rotation_matrix_transpose[1][1]
+    },
+    {
+      RC[1][0] *rotation_matrix_transpose[0][0] + RC[1][1] *rotation_matrix_transpose[1][0],
+      RC[1][0] *rotation_matrix_transpose[0][1] + RC[1][1] *rotation_matrix_transpose[1][1]
+    }
+  };
+
+  double dev[2] = {x[0] - mu[0], x[1] - mu[1]};
+  double dev_covinv[2] = {dev[0] *rotated_cov_inv[0][0] + dev[1] *rotated_cov_inv[0][1],
+                          dev[0] *rotated_cov_inv[1][0] + dev[1] *rotated_cov_inv[1][1]
+                         };
+  double dev_covinv_dev = dev_covinv[0] * dev[0] + dev_covinv[1] * dev[1];
+  return -0.5 * dev_covinv_dev;
+}
+
+
+MatrixType cholesky(const MatrixType &A)
+{
+  MatrixType L(2, 2);
+  L(0, 0) = sqrt(A(0, 0));
+  L(1, 0) = A(1, 0) / L(0, 0);
+  L(1, 1) = sqrt(A(1, 1) - pow(L(1, 0), 2));
+  L(0, 1) = 0;
+  return L;
+}
+
+
+std::pair<SampleType, double> perturb (const SampleType &x, const MatrixType &cov)
+{
+  static std::mt19937 rng;
+  std::normal_distribution<double> dist(0, 2.88);
+  VectorType delta(2);
+  delta(0) = dist(rng);
+  delta(1) = dist(rng);
+  VectorType perturbation(2);
+
+  if (int(cov.size1()) > 0 && cov(0, 0) != 0)
+    {
+      MatrixType L = cholesky(cov);
+      perturbation = boost::numeric::ublas::prod(L, delta);
+    }
+  else
+    {
+      perturbation(0) = delta(0);
+      perturbation(1) = delta(1);
+    }
+
+  SampleType y = x;
+  y[0] = x[0] + perturbation(0);
+  y[1] = x[1] + perturbation(1);
+  return {y, 1.0};
+}
+
+
+int main ()
+{
+  SampleFlow::Producers::MetropolisHastings<SampleType> mh_sampler;
+  SampleFlow::Consumers::CovarianceMatrix<SampleType> cov_matrix;
+  SampleFlow::Consumers::MeanValue<SampleType> mean_value;
+  cov_matrix.connect_to_producer(mh_sampler);
+  mean_value.connect_to_producer(mh_sampler);
+  // Sample, starting at an asymmetric point, and creating 100,000 samples
+  mh_sampler.sample(
+  {5, -1},
+  &log_likelihood,
+  [&cov_matrix](const SampleType &x)
+  {
+    return perturb(x, cov_matrix.get());
+  },
+  10000
+  );
+  std::cout << "Mean value = " << mean_value.get()[0] << std::endl;
+  std::cout << "Mean value = " << mean_value.get()[1] << std::endl;
+  std::cout << "Covariance = " << cov_matrix.get()(0, 0) << std::endl;
+  std::cout << "Covariance = " << cov_matrix.get()(0, 1) << std::endl;
+  std::cout << "Covariance = " << cov_matrix.get()(1, 0) << std::endl;
+  std::cout << "Covariance = " << cov_matrix.get()(1, 1) << std::endl;
+}
diff --git a/tests/metropolis_hasting_producer_13.output b/tests/metropolis_hasting_producer_13.output
new file mode 100644
index 00000000..2dca29aa
--- /dev/null
+++ b/tests/metropolis_hasting_producer_13.output
@@ -0,0 +1,6 @@
+Mean value = 0.181337
+Mean value = -0.041949
+Covariance = 9.31345
+Covariance = -4.3749
+Covariance = -4.3749
+Covariance = 3.42076