Create the zip before

DoTests.ps1

@@ -1,5 +1,9 @@
 $PSVersionTable.PSVersion
 
+## Create the zip before the tests run
+## Otherwise the EPPlus.dll is in use after the Pester run
+Compress-Archive -Path . -DestinationPath .\ImportExcel.zip
+
 if ((Get-Module -ListAvailable pester) -eq $null) {
     Install-Module -Name Pester -Repository PSGallery -Force
 }
@@ -8,6 +12,4 @@ $result = Invoke-Pester -Script $PSScriptRoot\__tests__ -Verbose -PassThru
 
 if ($result.FailedCount -gt 0) {
     throw "$($result.FailedCount) tests failed."
-}
-
-Compress-Archive -Path . -DestinationPath .\ImportExcel.zip
+}