Defensive approach to avoid duplicates. Duplicate check test

Author: hjgraca

libraries/src/AWS.Lambda.Powertools.Common/Core/SystemWrapper.cs

@@ -94,19 +94,25 @@ public void SetEnvironmentVariable(string variable, string value)
     public void SetExecutionEnvironment<T>(T type)
     {
         const string envName = Constants.AwsExecutionEnvironmentVariableName;
-
         var envValue = new StringBuilder();
-
+        var currentEnvValue = GetEnvironmentVariable(envName);
+        var assemblyName = ParseAssemblyName(_powertoolsEnvironment.GetAssemblyName(type));
+        
         // If there is an existing execution environment variable add the annotations package as a suffix.
-        if(!string.IsNullOrEmpty(GetEnvironmentVariable(envName)))
+        if(!string.IsNullOrEmpty(currentEnvValue))
         {
-            envValue.Append($"{GetEnvironmentVariable(envName)} ");
+            // Avoid duplication - should not happen since the calling Instances are Singletons - defensive purposes
+            if (currentEnvValue.Contains(assemblyName))
+            {
+                return;
+            }
+            
+            envValue.Append($"{currentEnvValue} ");
         }
 
         var assemblyVersion = _powertoolsEnvironment.GetAssemblyVersion(type);
-        var assemblyName =_powertoolsEnvironment.GetAssemblyName(type);
-
-        envValue.Append($"{ParseAssemblyName(assemblyName)}/{assemblyVersion}");
+        
+        envValue.Append($"{assemblyName}/{assemblyVersion}");
 
         SetEnvironmentVariable(envName, envValue.ToString());
     }

libraries/tests/AWS.Lambda.Powertools.Common.Tests/Core/PowertoolsEnvironmentTest.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Reflection;
+using Moq;
 using Xunit;
 
 namespace AWS.Lambda.Powertools.Common.Tests;
@@ -42,10 +44,9 @@ public void Set_Multiple_Execution_Environment()
 
         // Act
         systemWrapper.SetExecutionEnvironment(this);
-        systemWrapper.SetExecutionEnvironment(this);
 
         // Assert
-        Assert.Equal($"{Constants.FeatureContextIdentifier}/Fake/1.0.0 {Constants.FeatureContextIdentifier}/Fake/1.0.0", systemWrapper.GetEnvironmentVariable("AWS_EXECUTION_ENV"));
+        Assert.Equal($"{Constants.FeatureContextIdentifier}/Fake/1.0.0", systemWrapper.GetEnvironmentVariable("AWS_EXECUTION_ENV"));
     }
 
     [Fact]
@@ -63,6 +64,20 @@ public void Set_Execution_Real_Environment()
 
     [Fact]
     public void Set_Execution_Real_Environment_Multiple()
+    {
+        // Arrange
+        var systemWrapper = new SystemWrapper(new PowertoolsEnvironment());
+
+        // Act
+        systemWrapper.SetExecutionEnvironment(this);
+        systemWrapper.SetExecutionEnvironment(systemWrapper);
+
+        // Assert
+        Assert.Equal($"{Constants.FeatureContextIdentifier}/Tests/1.0.0 {Constants.FeatureContextIdentifier}/Common/0.0.1", systemWrapper.GetEnvironmentVariable("AWS_EXECUTION_ENV"));
+    }
+    
+    [Fact]
+    public void Set_Execution_Real_Environment_Multiple_Avoid_Duplicate()
     {
         // Arrange
         var systemWrapper = new SystemWrapper(new PowertoolsEnvironment());
@@ -72,7 +87,7 @@ public void Set_Execution_Real_Environment_Multiple()
         systemWrapper.SetExecutionEnvironment(this);
 
         // Assert
-        Assert.Equal($"{Constants.FeatureContextIdentifier}/Tests/1.0.0 {Constants.FeatureContextIdentifier}/Tests/1.0.0", systemWrapper.GetEnvironmentVariable("AWS_EXECUTION_ENV"));
+        Assert.Equal($"{Constants.FeatureContextIdentifier}/Tests/1.0.0", systemWrapper.GetEnvironmentVariable("AWS_EXECUTION_ENV"));
     }
 
     public void Dispose()