@@ -1,5 +1,6 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using System;
+using System.Linq;
 using Tensorflow;
 using static Tensorflow.Binding;
 
@@ -23,7 +24,7 @@ public void SimpleWhileLoop()
         private void _testWhileContextHelper(int maximum_iterations)
         {
             // TODO: implement missing code dependencies
-            var sess = this.cached_session();
+            using var sess = this.cached_session();
             var i = constant_op.constant(0, name: "i");
             var c = new Func<Tensor, Tensor>(x => gen_math_ops.less(x, ops.convert_to_tensor(10), name: "c"));
             var b = new Func<Tensor, Tensor>(x => math_ops.add(x, 1, name: "c"));
 
@@ -388,22 +388,21 @@ public void testBoundaryStop()
 
         }
 
-        [Ignore("TODO")]
         [TestMethod]
         public void testBoundaryContinue()
         {
-            //@test_util.run_v1_only("b/120545219")
-            //def testBoundaryContinue(self):
-            //  # Test that we differentiate both 'x' and 'y' correctly when x is a
-            //  # predecessor of y.
-            //  with self.cached_session():
-            //    x = constant(1.0)
-            //    y = x * 2.0
-            //    z = y * 3.0
-            //    grads = gradients.gradients(z, [x, y])
-            //    self.assertTrue(all(x is not None for x in grads))
-            //    self.assertEqual(6.0, grads[0].eval())
+            // Test that we differentiate both 'x' and 'y' correctly when x is a
+            // predecessor of y.
 
+            using (self.cached_session())
+            {
+                var x = tf.constant(1.0);
+                var y = x * 2.0;
+                var z = y * 3.0;
+                var grads = tf.gradients(z, new[] { x, y });
+                self.assertTrue(all(grads.Select(x => x != null)));
+                self.assertEqual(6.0, grads[0].eval());
+            }   
         }
 
         [Ignore("TODO")]
 
@@ -6,6 +6,8 @@
 using System.Linq;
 using Tensorflow;
 using static Tensorflow.Binding;
+using OneOf.Types;
+using System.Collections.Generic;
 
 namespace TensorFlowNET.UnitTest
 {
@@ -139,6 +141,21 @@ public void assertProtoEquals(object toProto, object o)
 
         #region tensor evaluation and test session
 
+        private Session _cached_session = null;
+        private Graph _cached_graph = null;
+        private object _cached_config = null;
+        private bool _cached_force_gpu = false;
+
+        private void _ClearCachedSession()
+        {
+            if (self._cached_session != null)
+            {
+                self._cached_session.Dispose();
+                self._cached_session = null;
+            }
+        }
+
+
         //protected object _eval_helper(Tensor[] tensors)
         //{
         //    if (tensors == null)
@@ -203,10 +220,56 @@ public T evaluate<T>(Tensor tensor)
             }
         }
 
-
-        public Session cached_session()
+        ///Returns a TensorFlow Session for use in executing tests.
+        public Session cached_session(
+            Graph graph = null, object config = null, bool use_gpu = false, bool force_gpu = false)
         {
-            throw new NotImplementedException();
+            // This method behaves differently than self.session(): for performance reasons
+            // `cached_session` will by default reuse the same session within the same
+            // test.The session returned by this function will only be closed at the end
+            // of the test(in the TearDown function).
+
+            // Use the `use_gpu` and `force_gpu` options to control where ops are run.If
+            // `force_gpu` is True, all ops are pinned to `/ device:GPU:0`. Otherwise, if
+            // `use_gpu` is True, TensorFlow tries to run as many ops on the GPU as
+            // possible.If both `force_gpu and `use_gpu` are False, all ops are pinned to
+            // the CPU.
+
+            // Example:
+            // python
+            // class MyOperatorTest(test_util.TensorFlowTestCase) :
+            //   def testMyOperator(self):
+            //     with self.cached_session() as sess:
+            //       valid_input = [1.0, 2.0, 3.0, 4.0, 5.0]
+            //     result = MyOperator(valid_input).eval()
+            //       self.assertEqual(result, [1.0, 2.0, 3.0, 5.0, 8.0]
+            //       invalid_input = [-1.0, 2.0, 7.0]
+            //     with self.assertRaisesOpError("negative input not supported"):
+            //         MyOperator(invalid_input).eval()
+
+
+            // Args:
+            //   graph: Optional graph to use during the returned session.
+            //   config: An optional config_pb2.ConfigProto to use to configure the
+            //     session.
+            //   use_gpu: If True, attempt to run as many ops as possible on GPU.
+            //   force_gpu: If True, pin all ops to `/device:GPU:0`.
+
+            // Yields:
+            //   A Session object that should be used as a context manager to surround
+            //   the graph building and execution code in a test case.
+
+
+            // TODO:
+            //  if context.executing_eagerly():
+            //    return self._eval_helper(tensors)
+            //  else:
+            {
+                var sess = self._get_cached_session(
+                    graph, config, force_gpu, crash_if_inconsistent_args: true);
+                using var cached = self._constrain_devices_and_set_default(sess, use_gpu, force_gpu);
+                return cached; 
+            }
         }
 
         //Returns a TensorFlow Session for use in executing tests.
@@ -254,6 +317,39 @@ public Session session(Graph graph = null, object config = null, bool use_gpu =
             return s.as_default();
         }
 
+        private Session _constrain_devices_and_set_default(Session sess, bool use_gpu, bool force_gpu)
+        {
+            // Set the session and its graph to global default and constrain devices."""
+            if (tf.executing_eagerly())
+                return null;
+            else {
+                sess.graph.as_default();
+                sess.as_default();
+                {
+                    if (force_gpu)
+                    {
+                        // TODO:
+
+                        // Use the name of an actual device if one is detected, or
+                        // '/device:GPU:0' otherwise
+                        /* var gpu_name = gpu_device_name();
+                        if (!gpu_name)
+                            gpu_name = "/device:GPU:0"
+                        using (sess.graph.device(gpu_name)) {
+                            yield return sess;
+                        }*/
+                        return sess;
+                    }
+                    else if (use_gpu)
+                        return sess;
+                    else 
+                        using (sess.graph.device("/device:CPU:0"))
+                            return sess;
+                }
+                
+            }
+        }
+
         // See session() for details.
         private Session _create_session(Graph graph, object cfg, bool forceGpu)
         {
@@ -298,6 +394,50 @@ private Session _create_session(Graph graph, object cfg, bool forceGpu)
             return new Session(graph);//, config = prepare_config(config))
         }
 
+        private Session _get_cached_session(
+                          Graph graph = null,
+                          object config = null,
+                          bool force_gpu = false,
+                          bool crash_if_inconsistent_args = true)
+        {
+            // See cached_session() for documentation.
+            if (self._cached_session == null)
+            {
+                var sess = self._create_session(graph, config, force_gpu);
+                self._cached_session = sess;
+                self._cached_graph = graph;
+                self._cached_config = config;
+                self._cached_force_gpu = force_gpu;
+                return sess;
+            } else {
+
+                if (crash_if_inconsistent_args && !self._cached_graph.Equals(graph))
+                    throw new ValueError(@"The graph used to get the cached session is 
+                                           different than the one that was used to create the
+                                           session. Maybe create a new session with 
+                                           self.session()");
+                if (crash_if_inconsistent_args && !self._cached_config.Equals(config)) {
+                    throw new ValueError(@"The config used to get the cached session is 
+                                           different than the one that was used to create the 
+                                           session. Maybe create a new session with 
+                                           self.session()");
+                }
+                if (crash_if_inconsistent_args && !self._cached_force_gpu.Equals(force_gpu)) {
+                    throw new ValueError(@"The force_gpu value used to get the cached session is 
+                                           different than the one that was used to create the 
+                                           session. Maybe create a new session with 
+                                           self.session()");
+                }
+                return _cached_session;
+            }
+        }
+
+        [TestCleanup]
+        public void Cleanup()
+        {
+            _ClearCachedSession();
+        }
+
         #endregion
 
         public void AssetSequenceEqual<T>(T[] a, T[] b)