Added pester test for Invoke-Expression

src/pester-tests/Invoke-Expression.Tests.ps1

@@ -0,0 +1,31 @@
+$here = Split-Path -Parent $MyInvocation.MyCommand.Path
+
+Describe "Invoke-Expression" {
+    
+    Context "Should execute the invoked command validly" {
+
+        It "Should return the echoed text" {
+            (Invoke-Expression -command "echo pestertest1") | Should be "pestertest1"
+        }
+
+        It "Should return the echoed text for the alias" {
+            (iex -command "echo pestertest2") | Should Be "pestertest2" 
+        }
+
+        It "Should return the echoed text from a script" {
+            $testfile = "$here/assets/echoscript.ps1"
+            $testcommand = "echo pestertestscript"
+            $testcommand | Add-Content -Path $testfile
+            (Invoke-Expression $testfile) | Should Be "pestertestscript"
+            Remove-Item $testfile
+        }
+
+        It "Should return the echoed text from a script from the alias" {
+            $testfile = "$here/assets/echoscript.ps1"
+            $testcommand = "echo pestertestscript"
+            $testcommand | Add-Content -Path $testfile
+            (iex $testfile) | Should Be "pestertestscript"
+            Remove-Item $testfile
+        }
+    }
+}