diff --git a/src/Adapter/MSTestAdapter/Execution/TestExecutionManager.cs b/src/Adapter/MSTestAdapter/Execution/TestExecutionManager.cs
index ce183cdb87..cf55868270 100644
--- a/src/Adapter/MSTestAdapter/Execution/TestExecutionManager.cs
+++ b/src/Adapter/MSTestAdapter/Execution/TestExecutionManager.cs
@@ -102,8 +102,11 @@ public void RunTests(IEnumerable<string> sources, IRunContext runContext, IFrame
                 var logger = (IMessageLogger)frameworkHandle;
                 
                 // discover the tests
-                (new UnitTestDiscoverer()).DiscoverTestsInSource(source, logger, discoverySink, runContext?.RunSettings);
+                this.GetUnitTestDiscoverer().DiscoverTestsInSource(source, logger, discoverySink, runContext?.RunSettings);
                 tests.AddRange(discoverySink.Tests);
+
+                //Clear discoverSinksTests so that it just stores test for one source at one point of time
+                discoverySink.Tests.Clear();
             }
 
             bool isDeploymentDone = PlatformServiceProvider.Instance.TestDeployment.Deploy(tests, runContext, frameworkHandle);
@@ -123,7 +126,7 @@ public void RunTests(IEnumerable<string> sources, IRunContext runContext, IFrame
         /// <summary>
         /// Execute the parameter tests
         /// </summary>
-        private void ExecuteTests(IEnumerable<TestCase> tests, IRunContext runContext, IFrameworkHandle frameworkHandle, bool isDeploymentDone)
+        internal virtual void ExecuteTests(IEnumerable<TestCase> tests, IRunContext runContext, IFrameworkHandle frameworkHandle, bool isDeploymentDone)
         {
             var testsBySource = (from test in tests
                                  group test by test.Source into testGroup
@@ -277,6 +280,11 @@ private void ExecuteTestsWithTestRunner(
             this.LogWarnings(testExecutionRecorder, warnings);
         }
 
+        internal virtual UnitTestDiscoverer GetUnitTestDiscoverer()
+        {
+            return new UnitTestDiscoverer();
+        } 
+
         private void CacheSessionParameters(IRunContext runContext, ITestExecutionRecorder testExecutionRecorder)
         {
             if (!string.IsNullOrEmpty(runContext?.RunSettings?.SettingsXml))
diff --git a/src/Adapter/MSTestAdapter/MSTestDiscoverer.cs b/src/Adapter/MSTestAdapter/MSTestDiscoverer.cs
index d0f6dcd250..8f4ec645f2 100644
--- a/src/Adapter/MSTestAdapter/MSTestDiscoverer.cs
+++ b/src/Adapter/MSTestAdapter/MSTestDiscoverer.cs
@@ -117,7 +117,7 @@ internal void DiscoverTests(
         /// <param name="logger"> The logger. </param>
         /// <param name="discoverySink"> The discovery Sink. </param>
         /// <param name="runSettings"> The run settings. </param>
-        internal void DiscoverTestsInSource(
+        internal virtual void DiscoverTestsInSource(
             string source,
             IMessageLogger logger,
             ITestCaseDiscoverySink discoverySink,
diff --git a/test/UnitTests/MSTestAdapter.Tests/Discovery/UnitTestDiscovererTests.cs b/test/UnitTests/MSTestAdapter.Tests/Discovery/UnitTestDiscovererTests.cs
index f269ab4933..7e8e758b42 100644
--- a/test/UnitTests/MSTestAdapter.Tests/Discovery/UnitTestDiscovererTests.cs
+++ b/test/UnitTests/MSTestAdapter.Tests/Discovery/UnitTestDiscovererTests.cs
@@ -261,4 +261,18 @@ public DummyNavigationData(string fileName, int minLineNumber, int maxLineNumber
 
         public int MaxLineNumber { get; set; }
     }
+
+    internal class TestableUnitTestDiscoverer : UnitTestDiscoverer
+    {
+        internal override void DiscoverTestsInSource(string source,
+            IMessageLogger logger,
+            ITestCaseDiscoverySink discoverySink,
+            IRunSettings runSettings)
+        {
+            var testCase1 = new TestCase("A", new System.Uri("executor://testExecutor"), source);
+            var testCase2 = new TestCase("B", new System.Uri("executor://testExecutor"), source);
+            discoverySink.SendTestCase(testCase1);
+            discoverySink.SendTestCase(testCase2);
+        }
+    }
 }
\ No newline at end of file
diff --git a/test/UnitTests/MSTestAdapter.Tests/Execution/TestExecutionManagerTests.cs b/test/UnitTests/MSTestAdapter.Tests/Execution/TestExecutionManagerTests.cs
index 8c8ba87964..9c25793a7a 100644
--- a/test/UnitTests/MSTestAdapter.Tests/Execution/TestExecutionManagerTests.cs
+++ b/test/UnitTests/MSTestAdapter.Tests/Execution/TestExecutionManagerTests.cs
@@ -23,6 +23,7 @@ namespace Microsoft.VisualStudio.TestPlatform.MSTestAdapter.UnitTests.Execution
 
     using Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution;
     using Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.ObjectModel;
+    using Microsoft.VisualStudio.TestPlatform.MSTestAdapter.UnitTests.Discovery;
     using Microsoft.VisualStudio.TestPlatform.MSTestAdapter.UnitTests.TestableImplementations;
     using Microsoft.VisualStudio.TestPlatform.ObjectModel;
     using Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter;
@@ -352,6 +353,22 @@ public void RunTestsForSourceShouldPassInDeploymentInformationAsPropertiesToTheT
             Assert.IsNotNull(DummyTestClass.TestContextProperties);
         }
 
+        [TestMethodV1]
+        public void RunTestsForMultipleSourcesShouldRunEachTestJustOnce()
+        {
+            int testsCount = 0;
+            var sources = new List<string> { Assembly.GetExecutingAssembly().Location, Assembly.GetExecutingAssembly().Location };
+            TestableTestExecutionManager testableTestExecutionmanager = new TestableTestExecutionManager();
+
+            testableTestExecutionmanager.ExecuteTestsWrapper = (tests, runContext, frameworkHandle, isDeploymentDone) =>
+            {
+                testsCount += tests.Count();
+            };
+
+            testableTestExecutionmanager.RunTests(sources, this.runContext, this.frameworkHandle, this.cancellationToken);
+            Assert.AreEqual(testsCount, 4);
+        }
+
         #endregion
 
         #region private methods
@@ -567,6 +584,24 @@ public bool MatchTestCase(TestCase testCase, Func<string, object> propertyValueP
             }
         }
 
+        internal class TestableTestExecutionManager : TestExecutionManager
+        {
+            internal override void ExecuteTests(IEnumerable<TestCase> tests, IRunContext runContext,
+                IFrameworkHandle frameworkHandle, bool isDeploymentDone)
+            {
+                if (this.ExecuteTestsWrapper != null)
+                {
+                    this.ExecuteTestsWrapper.Invoke(tests, runContext, frameworkHandle, isDeploymentDone);
+                }
+            }
+
+            internal override UnitTestDiscoverer GetUnitTestDiscoverer()
+            {
+                return new TestableUnitTestDiscoverer();
+            }
+
+            internal Action<IEnumerable<TestCase>, IRunContext, IFrameworkHandle, bool> ExecuteTestsWrapper;
+        }
         #endregion
     }
 }