diff --git a/lib/decompress.ps1 b/lib/decompress.ps1
index 7313d4c9ac..a96ec5e015 100644
--- a/lib/decompress.ps1
+++ b/lib/decompress.ps1
@@ -1,123 +1,208 @@
-function requires_7zip($manifest, $architecture) {
-    foreach($dlurl in @(url $manifest $architecture)) {
-        if(file_requires_7zip $dlurl) { return $true }
+function Test-7ZipRequirement {
+    [CmdletBinding(DefaultParameterSetName = "URL")]
+    [OutputType([Boolean])]
+    param(
+        [Parameter(Mandatory = $true, ParameterSetName = "URL")]
+        [String[]]
+        $URL,
+        [Parameter(Mandatory = $true, ParameterSetName = "File")]
+        [String]
+        $File
+    )
+    if ($URL) {
+        if (get_config 7ZIPEXTRACT_USE_EXTERNAL) {
+            return $false
+        } else {
+            return ($URL | Where-Object { Test-7ZipRequirement -File $_ }).Count -gt 0
+        }
+    } else {
+        return $File -match '\.((gz)|(tar)|(tgz)|(lzma)|(bz)|(bz2)|(7z)|(rar)|(iso)|(xz)|(lzh)|(nupkg))$'
     }
 }
 
-function requires_lessmsi ($manifest, $architecture) {
-    $useLessMsi = get_config MSIEXTRACT_USE_LESSMSI
-    if (!$useLessMsi) { return $false }
-
-    $(url $manifest $architecture | Where-Object {
-        $_ -match '\.(msi)$'
-    } | Measure-Object | Select-Object -exp count) -gt 0
-}
-
-function file_requires_7zip($fname) {
-    $fname -match '\.((gz)|(tar)|(tgz)|(lzma)|(bz)|(bz2)|(7z)|(rar)|(iso)|(xz)|(lzh)|(nupkg))$'
-}
-
-function extract_7zip($path, $to, $recurse) {
-    $output = 7z x "$path" -o"$to" -y
-    if($lastexitcode -ne 0) { abort "Exit code was $lastexitcode." }
-
-    # check for tar
-    $tar = (split-path $path -leaf) -replace '\.[^\.]*$', ''
-    if($tar -match '\.tar$') {
-        if(test-path "$to\$tar") { extract_7zip "$to\$tar" $to $true }
+function Test-LessMSIRequirement {
+    [CmdletBinding()]
+    [OutputType([Boolean])]
+    param(
+        [Parameter(Mandatory = $true)]
+        [String[]]
+        $URL
+    )
+    if (get_config MSIEXTRACT_USE_LESSMSI) {
+        return ($URL | Where-Object { $_ -match '\.msi$' }).Count -gt 0
+    } else {
+        return $false
     }
-
-    if($recurse) { Remove-Item $path } # clean up intermediate files
-}
-
-function extract_msi($path, $to) {
-    $logfile = "$(split-path $path)\msi.log"
-    $ok = run 'msiexec' @('/a', "`"$path`"", '/qn', "TARGETDIR=`"$to`"", "/lwe `"$logfile`"")
-    if(!$ok) { abort "Failed to extract files from $path.`nLog file:`n  $(friendly_path $logfile)" }
-    if(test-path $logfile) { Remove-Item $logfile }
 }
 
-function lessmsi_config ($extract_dir) {
-    $extract_fn = 'extract_lessmsi'
-    if ($extract_dir) {
-        $extract_dir = join-path SourceDir $extract_dir
+function Expand-7ZipArchive {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]
+        [String]
+        $Path,
+        [Parameter(Position = 1)]
+        [String]
+        $DestinationPath = (Split-Path $Path),
+        [Switch]
+        $Removal
+    )
+    $LogLocation = "$(Split-Path $Path)\7zip.log"
+    if (get_config 7ZIPEXTRACT_USE_EXTERNAL) {
+        try {
+            7z x "$Path" -o"$DestinationPath" -y | Out-File $LogLocation
+        } catch [System.Management.Automation.CommandNotFoundException] {
+            abort "Cannot find external 7Zip (7z.exe) while '7ZIPEXTRACT_USE_EXTERNAL' is 'true'!`nRun 'scoop config 7ZIPEXTRACT_USE_EXTERNAL false' or install 7Zip manually and try again."
+        }
     } else {
-        $extract_dir = "SourceDir"
+        &(file_path 7zip 7z.exe) x "$Path" -o"$DestinationPath" -y | Out-File $LogLocation
+    }
+    if ($LASTEXITCODE -ne 0) {
+        abort "Failed to extract files from $Path.`nLog file:`n  $(friendly_path $LogLocation)"
+    }
+    if (Test-Path $LogLocation) {
+        Remove-Item $LogLocation -Force
+    }
+    if ((strip_ext $Path) -match '\.tar$' -or $Path -match '\.tgz$') {
+        # Check for tar
+        $ArchivedFile = &(file_path 7zip 7z.exe) l "$Path"
+        if ($LASTEXITCODE -eq 0) {
+            $TarFile = $ArchivedFile[-3] -replace '.{53}(.*)', '$1' # get inner tar file name
+            Expand-7ZipArchive "$DestinationPath\$TarFile" $DestinationPath -Removal
+        } else {
+            abort "Failed to list files in $Path.`nNot a 7Zip supported archive file."
+        }
+    }
+    if ($Removal) {
+        # Remove original archive file
+        Remove-Item $Path -Force
     }
-
-    $extract_fn, $extract_dir
 }
 
-function extract_lessmsi($path, $to) {
-    Invoke-Expression "lessmsi x `"$path`" `"$to\`""
+function Expand-MSIArchive {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]
+        [String]
+        $Path,
+        [Parameter(Position = 1)]
+        [String]
+        $DestinationPath = (Split-Path $Path),
+        [Switch]
+        $Removal
+    )
+    $LogLocation = "$(Split-Path $Path)\msi.log"
+    if (get_config MSIEXTRACT_USE_LESSMSI) {
+        &(file_path lessmsi lessmsi.exe) x "$Path" "$DestinationPath\" | Out-File $LogLocation
+        if ($LASTEXITCODE -ne 0) {
+            abort "Failed to extract files from $Path.`nLog file:`n  $(friendly_path $LogLocation)"
+        }
+        if (Test-Path "$DestinationPath\SourceDir") {
+            movedir "$DestinationPath\SourceDir" "$DestinationPath" | Out-Null
+        }
+    } else {
+        $ok = run 'msiexec' @('/a', "`"$Path`"", '/qn', "TARGETDIR=`"$DestinationPath`"", "/lwe `"$LogLocation`"")
+        if (!$ok) {
+            abort "Failed to extract files from $Path.`nLog file:`n  $(friendly_path $LogLocation)"
+        }
+        Remove-Item "$DestinationPath\$(fname $Path)" -Force
+    }
+    if (Test-Path $LogLocation) {
+        Remove-Item $LogLocation -Force
+    }
+    if ($Removal) {
+        # Remove original archive file
+        Remove-Item $Path -Force
+    }
 }
 
-function unpack_inno($fname, $manifest, $dir) {
-    if (!$manifest.innosetup) { return }
-
-    write-host "Unpacking innosetup... " -nonewline
-    innounp -x -d"$dir\_scoop_unpack" "$dir\$fname" > "$dir\innounp.log"
-    if ($lastexitcode -ne 0) {
-        abort "Failed to unpack innosetup file. See $dir\innounp.log"
+function Expand-InnoArchive {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]
+        [String]
+        $Path,
+        [Parameter(Position = 1)]
+        [String]
+        $DestinationPath = (Split-Path $Path),
+        [Switch]
+        $Removal
+    )
+    $LogLocation = "$(Split-Path $Path)\innounp.log"
+    &(file_path innounp innounp.exe) -x -d"$DestinationPath" -c'{app}' "$Path" -y | Out-File $LogLocation
+    if ($LASTEXITCODE -ne 0) {
+        abort "Failed to extract files from $Path.`nLog file:`n  $(friendly_path $LogLocation)"
+    }
+    if (Test-Path $LogLocation) {
+        Remove-Item $LogLocation -Force
+    }
+    if ($Removal) {
+        # Remove original archive file
+        Remove-Item $Path -Force
     }
-
-    Get-ChildItem "$dir\_scoop_unpack\{app}" -r | Move-Item -dest "$dir" -force
-
-    Remove-Item -r -force "$dir\_scoop_unpack"
-
-    Remove-Item "$dir\$fname"
-    Write-Host "done." -f Green
 }
 
-function extract_zip($path, $to) {
-    if (!(test-path $path)) { abort "can't find $path to unzip"}
-    try { add-type -assembly "System.IO.Compression.FileSystem" -ea stop }
-    catch { unzip_old $path $to; return } # for .net earlier than 4.5
-    $retries = 0
-    while ($retries -le 10) {
-        if ($retries -eq 10) {
+function Expand-ZipArchive {
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]
+        [String]
+        $Path,
+        [Parameter(Position = 1)]
+        [String]
+        $DestinationPath = (Split-Path $Path),
+        [Switch]
+        $Removal
+    )
+    # All methods to unzip the file require .NET4.5+
+    if ($PSVersionTable.PSVersion.Major -lt 5) {
+        Add-Type -AssemblyName System.IO.Compression.FileSystem
+        try {
+            [System.IO.Compression.ZipFile]::ExtractToDirectory($Path, $DestinationPath)
+        } catch [System.IO.PathTooLongException] {
+            # try to fall back to 7zip if path is too long
             if (7zip_installed) {
-                extract_7zip $path $to $false
+                Expand-7ZipArchive $Path $DestinationPath -Removal
                 return
             } else {
-                abort "Unzip failed: Windows can't unzip because a process is locking the file.`nRun 'scoop install 7zip' and try again."
+                abort "Unzip failed: Windows can't handle the long paths in this zip file.`nRun 'scoop install 7zip' and try again."
             }
+        } catch [System.IO.IOException] {
+            if (7zip_installed) {
+                Expand-7ZipArchive $Path $DestinationPath -Removal
+                return
+            } else {
+                abort "Unzip failed: Windows can't handle the file names in this zip file.`nRun 'scoop install 7zip' and try again."
+            }
+        } catch {
+            abort "Unzip failed: $_"
         }
-        if (isFileLocked $path) {
-            write-host "Waiting for $path to be unlocked by another process... ($retries/10)"
-            $retries++
-            Start-Sleep -s 2
-        } else {
-            break
-        }
+    } else {
+        # Use Expand-Archive to unzip in PowerShell 5+
+        Expand-Archive -Path $Path -DestinationPath $DestinationPath -Force
     }
-
-    try {
-        [io.compression.zipfile]::extracttodirectory($path, $to)
-    } catch [system.io.pathtoolongexception] {
-        # try to fall back to 7zip if path is too long
-        if (7zip_installed) {
-            extract_7zip $path $to $false
-            return
-        } else {
-            abort "Unzip failed: Windows can't handle the long paths in this zip file.`nRun 'scoop install 7zip' and try again."
-        }
-    } catch [system.io.ioexception] {
-        if (7zip_installed) {
-            extract_7zip $path $to $false
-            return
-        } else {
-            abort "Unzip failed: Windows can't handle the file names in this zip file.`nRun 'scoop install 7zip' and try again."
-        }
-    } catch {
-        abort "Unzip failed: $_"
+    if ($Removal) {
+        # Remove original archive file
+        Remove-Item $Path -Force
     }
 }
 
-function unzip_old($path, $to) {
-    # fallback for .net earlier than 4.5
-    $shell = (new-object -com shell.application -strict)
-    $zipfiles = $shell.namespace("$path").items()
-    $to = ensure $to
-    $shell.namespace("$to").copyHere($zipfiles, 4) # 4 = don't show progress dialog
+function extract_7zip($path, $to, $removal) {
+    Show-DeprecationMessage $MyInvocation 'Expand-7ZipArchive'
+    Expand-7ZipArchive -Path $path -DestinationPath $to -Removal:$removal
+}
+
+function extract_msi($path, $to, $removal) {
+    Show-DeprecationMessage $MyInvocation 'Expand-MSIArchive'
+    Expand-MSIArchive -Path $path -DestinationPath $to -Removal:$removal
+}
+
+function extract_inno($path, $to, $removal) {
+    Show-DeprecationMessage $MyInvocation 'Expand-InnoArchive'
+    Expand-InnoArchive -Path $path -DestinationPath $to -Removal:$removal
+}
+
+function extract_zip($path, $to, $removal) {
+    Show-DeprecationMessage $MyInvocation 'Expand-ZipArchive'
+    Expand-ZipArchive -Path $path -DestinationPath $to -Removal:$removal
 }
diff --git a/lib/depends.ps1 b/lib/depends.ps1
index f8cd2bdcbd..e6926abe1a 100644
--- a/lib/depends.ps1
+++ b/lib/depends.ps1
@@ -1,11 +1,11 @@
 # resolve dependencies for the supplied apps, and sort into the correct order
 function install_order($apps, $arch) {
     $res = @()
-    foreach($app in $apps) {
-        foreach($dep in deps $app $arch) {
-            if($res -notcontains $dep) { $res += $dep}
+    foreach ($app in $apps) {
+        foreach ($dep in deps $app $arch) {
+            if ($res -notcontains $dep) { $res += $dep}
         }
-        if($res -notcontains $app) { $res += $app }
+        if ($res -notcontains $app) { $res += $app }
     }
     return $res
 }
@@ -15,7 +15,7 @@ function deps($app, $arch) {
     $resolved = new-object collections.arraylist
     dep_resolve $app $arch $resolved @()
 
-    if($resolved.count -eq 1) { return @() } # no dependencies
+    if ($resolved.count -eq 1) { return @() } # no dependencies
     return $resolved[0..($resolved.count - 2)]
 }
 
@@ -33,9 +33,9 @@ function dep_resolve($app, $arch, $resolved, $unresolved) {
 
     $deps = @(install_deps $manifest $arch) + @(runtime_deps $manifest) | Select-Object -Unique
 
-    foreach($dep in $deps) {
-        if($resolved -notcontains $dep) {
-            if($unresolved -contains $dep) {
+    foreach ($dep in $deps) {
+        if ($resolved -notcontains $dep) {
+            if ($unresolved -contains $dep) {
                 abort "Circular dependency detected: '$app' -> '$dep'."
             }
             dep_resolve $dep $arch $resolved $unresolved
@@ -46,17 +46,15 @@ function dep_resolve($app, $arch, $resolved, $unresolved) {
 }
 
 function runtime_deps($manifest) {
-    if($manifest.depends) { return $manifest.depends }
+    if ($manifest.depends) { return $manifest.depends }
 }
 
 function install_deps($manifest, $arch) {
     $deps = @()
 
-    if((requires_7zip $manifest $arch) -and !(7zip_installed)) {
-        $deps += '7zip'
-    }
-    if(requires_lessmsi $manifest $arch) { $deps += 'lessmsi' }
-    if($manifest.innosetup) { $deps += 'innounp' }
+    if (Test-7ZipRequirement -URL (url $manifest $arch)) { $deps += '7zip' }
+    if (Test-LessMSIRequirement -URL (url $manifest $arch)) { $deps += 'lessmsi' }
+    if ($manifest.innosetup) { $deps += 'innounp' }
 
     return $deps
 }
diff --git a/lib/install.ps1 b/lib/install.ps1
index dbab39b7b4..69ec146fef 100644
--- a/lib/install.ps1
+++ b/lib/install.ps1
@@ -41,7 +41,6 @@ function install_app($app, $architecture, $global, $suggested, $use_cache = $tru
     $persist_dir = persistdir $app $global
 
     $fname = dl_urls $app $version $manifest $bucket $architecture $dir $use_cache $check_hash
-    unpack_inno $fname $manifest $dir
     pre_install $manifest $architecture
     run_installer $fname $manifest $architecture $dir $global
     ensure_install_dir_not_in_path $dir $global
@@ -103,7 +102,7 @@ function dl_with_cache($app, $version, $url, $to, $cookies = $null, $use_cache =
     $cached = fullpath (cache_path $app $version $url)
 
     if(!(test-path $cached) -or !$use_cache) {
-        $null = ensure $cachedir
+        ensure $cachedir | Out-Null
         do_dl $url "$cached.download" $cookies
         Move-Item "$cached.download" $cached -force
     } else { write-host "Loading $(url_remote_filename $url) from cache"}
@@ -532,39 +531,29 @@ function dl_urls($app, $version, $manifest, $bucket, $architecture, $dir, $use_c
 
         # work out extraction method, if applicable
         $extract_fn = $null
-        if($fname -match '\.zip$') {
-            $extract_fn = 'extract_zip'
+        if ($manifest.innosetup) {
+            $extract_fn = 'Expand-InnoArchive'
+        } elseif($fname -match '\.zip$') {
+            $extract_fn = 'Expand-ZipArchive'
         } elseif($fname -match '\.msi$') {
             # check manifest doesn't use deprecated install method
-            $msi = msi $manifest $architecture
-            if(!$msi) {
-                $useLessMsi = get_config MSIEXTRACT_USE_LESSMSI
-                if ($useLessMsi -eq $true) {
-                    $extract_fn, $extract_dir = lessmsi_config $extract_dir
-                }
-                else {
-                    $extract_fn = 'extract_msi'
-                }
-            } else {
+            if(msi $manifest $architecture) {
                 warn "MSI install is deprecated. If you maintain this manifest, please refer to the manifest reference docs."
+            } else {
+                $extract_fn = 'Expand-MSIArchive'
             }
-        } elseif(file_requires_7zip $fname) { # 7zip
-            if(!(7zip_installed)) {
-                warn "Aborting. You'll need to run 'scoop uninstall $app' to clean up."
-                abort "7-zip is required. You can install it with 'scoop install 7zip'."
-            }
-            $extract_fn = 'extract_7zip'
+        } elseif(Test-7ZipRequirement -File $fname) { # 7zip
+            $extract_fn = 'Expand-7ZipArchive'
         }
 
         if($extract_fn) {
             Write-Host "Extracting " -NoNewline
             Write-Host $fname -f Cyan -NoNewline
             Write-Host " ... " -NoNewline
-            $null = mkdir "$dir\_tmp"
-            & $extract_fn "$dir\$fname" "$dir\_tmp"
-            Remove-Item "$dir\$fname"
+            ensure "$dir\_tmp" | Out-Null
+            & $extract_fn "$dir\$fname" "$dir\_tmp" -Removal
             if ($extract_to) {
-                $null = mkdir "$dir\$extract_to" -force
+                ensure "$dir\$extract_to" | Out-Null
             }
             # fails if zip contains long paths (e.g. atom.json)
             #cp "$dir\_tmp\$extract_dir\*" "$dir\$extract_to" -r -force -ea stop
@@ -576,7 +565,7 @@ function dl_urls($app, $version, $manifest, $bucket, $architecture, $dir, $use_c
                 abort $(new_issue_msg $app $bucket "extract_dir error")
             }
 
-            if(test-path "$dir\_tmp") { # might have been moved by movedir
+            if(Test-Path "$dir\_tmp") { # might have been moved by movedir
                 try {
                     Remove-Item -r -force "$dir\_tmp" -ea stop
                 } catch [system.io.pathtoolongexception] {
@@ -1173,7 +1162,7 @@ function persist_data($manifest, $original_dir, $persist_dir) {
             # we don't have persist data in the store, move the source to target, then create link
             } elseif (Test-Path $source) {
                 # ensure target parent folder exist
-                $null = ensure (Split-Path -Path $target)
+                ensure (Split-Path -Path $target) | Out-Null
                 Move-Item $source $target
             # we don't have neither source nor target data! we need to crate an empty target,
             # but we can't make a judgement that the data should be a file or directory...
diff --git a/test/Scoop-Decompress.Tests.ps1 b/test/Scoop-Decompress.Tests.ps1
index 566258bd8b..d46d03f8f1 100644
--- a/test/Scoop-Decompress.Tests.ps1
+++ b/test/Scoop-Decompress.Tests.ps1
@@ -1,62 +1,152 @@
 . "$psscriptroot\Scoop-TestLib.ps1"
-. "$psscriptroot\..\lib\core.ps1"
 . "$psscriptroot\..\lib\decompress.ps1"
 . "$psscriptroot\..\lib\unix.ps1"
+. "$psscriptroot\..\lib\install.ps1"
+. "$psscriptroot\..\lib\manifest.ps1"
+. "$psscriptroot\..\lib\config.ps1"
 
 $isUnix = is_unix
 
-describe "unzip_old" -Tag 'Scoop' {
-    beforeall {
-        $working_dir = setup_working "unzip_old"
+function install_app_ci($app, $architecture) {
+    $manifest = manifest $app
+    $version = $manifest.version
+    $dir = ensure (versiondir $app $version)
+    $fname = dl_urls $app $version $manifest $null $architecture $dir
+    $dir = link_current $dir
+    success "'$app' ($version) was installed successfully!"
+}
+
+function test_extract($extract_fn, $from, $removal) {
+    $to = (strip_ext $from) -replace '\.tar$', ''
+    & $extract_fn ($from -replace '/', '\') ($to -replace '/', '\') -Removal:$removal
+    return $to
+}
+
+Describe 'Decompression function' -Tag 'Scoop', 'Decompress' {
+    BeforeAll {
+        $working_dir = setup_working 'decompress'
     }
 
-    function test-unzip($from) {
-        $to = strip_ext $from
+    if (!$isUnix) {
+        # Expanding Test Cases
+        $testcases = "$working_dir\TestCases.zip"
+        $testcases | Should -Exist
+        compute_hash $testcases 'sha256' | Should -Be '695bb18cafda52644a19afd184b2545e9c48f1a191f7ff1efc26cb034587079c'
+        Expand-Archive $testcases $working_dir
+    }
+
+    Context "7zip extraction" {
 
-        if(is_unix) {
-            unzip_old ($from -replace '\\','/') ($to -replace '\\','/')
-        } else {
-            unzip_old ($from -replace '/','\') ($to -replace '/','\')
+        if (!$isUnix) {
+            install_app_ci 7zip 64bit
+            $test1 = "$working_dir\7ZipTest1.7z"
+            $test2 = "$working_dir\7ZipTest2.tgz"
+            $test3 = "$working_dir\7ZipTest3.tar.bz2"
+            $test4 = "$working_dir\7ZipTest4.tar.gz"
         }
 
-        $to
-    }
+        It "extract normal compressed file" -Skip:$isUnix {
+            $to = test_extract "Expand-7ZipArchive" $test1
+            $to | Should -Exist
+            "$to\empty" | Should -Exist
+            (Get-ChildItem $to).Count | Should -Be 1
+        }
 
-    context "zip file size is zero bytes" {
-        $zerobyte = "$working_dir\zerobyte.zip"
-        $zerobyte | should -exist
+        It "extract nested compressed file" -Skip:$isUnix {
+            # file ext: tgz
+            $to = test_extract "Expand-7ZipArchive" $test2
+            $to | Should -Exist
+            "$to\empty" | Should -Exist
+            (Get-ChildItem $to).Count | Should -Be 1
 
-        it "unzips file with zero bytes without error" -skip:$isUnix {
-            # some combination of pester, COM (used within unzip_old), and Win10 causes a bugged return value from test-unzip
-            # `$to = test-unzip $zerobyte` * RETURN_VAL has a leading space and complains of $null usage when used in PoSH functions
-            $to = ([string](test-unzip $zerobyte)).trimStart()
+            # file ext: tar.bz2
+            $to = test_extract "Expand-7ZipArchive" $test3
+            $to | Should -Exist
+            "$to\empty" | Should -Exist
+            (Get-ChildItem $to).Count | Should -Be 1
+        }
 
-            $to | should -not -match '^\s'
-            $to | should -not -benullorempty
+        It "extract nested compressed file with different inner name" -Skip:$isUnix {
+            $to = test_extract "Expand-7ZipArchive" $test4
+            $to | Should -Exist
+            "$to\empty" | Should -Exist
+            (Get-ChildItem $to).Count | Should -Be 1
+        }
 
-            $to | should -exist
+        It "works with '-Removal' switch (`$removal param)" -Skip:$isUnix {
+            $test1 | Should -Exist
+            test_extract "Expand-7ZipArchive" $test1 $true
+            $test1 | Should -Not -Exist
+        }
+    }
+
+    Context "msi extraction" {
+        if (!$isUnix) {
+            install_app_ci lessmsi
+            $test1 = "$working_dir\MSITest.msi"
+            $test2 = "$working_dir\MSITestNull.msi"
+        }
 
-            (Get-ChildItem $to).count | should -be 0
+        It "extract normal MSI file" -Skip:$isUnix {
+            mock get_config { $false }
+            $to = test_extract "Expand-MSIArchive" $test1
+            $to | Should -Exist
+            "$to\MSITest\empty" | Should -Exist
+            (Get-ChildItem "$to\MSITest").Count | Should -Be 1
+        }
+
+        It "extract empty MSI file using lessmsi" -Skip:$isUnix {
+            mock get_config { $true }
+            $to = test_extract "Expand-MSIArchive" $test2
+            $to | Should -Exist
+        }
+
+        It "works with '-Removal' switch (`$removal param)" -Skip:$isUnix {
+            mock get_config { $false }
+            $test1 | Should -Exist
+            test_extract "Expand-MSIArchive" $test1 $true
+            $test1 | Should -Not -Exist
         }
     }
 
-    context "zip file is small in size" {
-        $small = "$working_dir\small.zip"
-        $small | should -exist
+    Context "inno extraction" {
 
-        it "unzips file which is small in size" -skip:$isUnix {
-            # some combination of pester, COM (used within unzip_old), and Win10 causes a bugged return value from test-unzip
-            # `$to = test-unzip $small` * RETURN_VAL has a leading space and complains of $null usage when used in PoSH functions
-            $to = ([string](test-unzip $small)).trimStart()
+        if (!$isUnix) {
+            install_app_ci innounp
+            $test = "$working_dir\InnoTest.exe"
+        }
 
-            $to | should -not -match '^\s'
-            $to | should -not -benullorempty
+        It "extract Inno Setup file" -Skip:$isUnix {
+            $to = test_extract "Expand-InnoArchive" $test
+            $to | Should -Exist
+            "$to\empty" | Should -Exist
+            (Get-ChildItem $to).Count | Should -Be 1
+        }
 
-            $to | should -exist
+        It "works with '-Removal' switch (`$removal param)" -Skip:$isUnix {
+            $test | Should -Exist
+            test_extract "Expand-InnoArchive" $test $true
+            $test | Should -Not -Exist
+        }
+    }
+
+    Context "zip extraction" {
+
+        if (!$isUnix) {
+            $test = "$working_dir\ZipTest.zip"
+        }
+
+        It "extract compressed file" -Skip:$isUnix {
+            $to = test_extract "Expand-ZipArchive" $test
+            $to | Should -Exist
+            "$to\empty" | Should -Exist
+            (Get-ChildItem $to).Count | Should -Be 1
+        }
 
-            # these don't work for some reason on appveyor
-            #join-path $to "empty" | should -exist
-            #(gci $to).count | should -be 1
+        It "works with '-Removal' switch (`$removal param)" -Skip:$isUnix {
+            $test | Should -Exist
+            test_extract "Expand-ZipArchive" $test $true
+            $test | Should -Not -Exist
         }
     }
 }
diff --git a/test/bin/test.ps1 b/test/bin/test.ps1
index 7413550acf..81e8c10318 100644
--- a/test/bin/test.ps1
+++ b/test/bin/test.ps1
@@ -10,40 +10,46 @@ $resultsXml = "$PSScriptRoot/TestResults.xml"
 $excludes = @()
 
 $splat = @{
-    Path = $TestPath
-    OutputFile = $resultsXml
+    Path         = $TestPath
+    OutputFile   = $resultsXml
     OutputFormat = 'NUnitXML'
-    PassThru = $true
+    PassThru     = $true
 }
 
-if($env:CI -eq $true) {
-    $commit = if($env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT) { $env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT } else { $env:APPVEYOR_REPO_COMMIT }
+if ($env:CI -eq $true) {
+    $commit = if ($env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT) { $env:APPVEYOR_PULL_REQUEST_HEAD_COMMIT } else { $env:APPVEYOR_REPO_COMMIT }
     $commitMessage = "$env:APPVEYOR_REPO_COMMIT_MESSAGE $env:APPVEYOR_REPO_COMMIT_MESSAGE_EXTENDED".TrimEnd()
 
-    if($commitMessage -match '!linter') {
+    if ($commitMessage -match '!linter') {
         Write-Warning "Skipping code linting per commit flag '!linter'"
         $excludes += 'Linter'
     }
 
     $changed_scripts = (Get-GitChangedFile -Include '*.ps1' -Commit $commit)
-    if(!$changed_scripts) {
+    if (!$changed_scripts) {
         Write-Warning "Skipping tests and code linting for *.ps1 files because they didn't change"
         $excludes += 'Linter'
         $excludes += 'Scoop'
     }
 
-    if($commitMessage -match '!manifests') {
+    $changed_scripts = (Get-GitChangedFile -Include '*decompress.ps1' -Commit $commit)
+    if (!$changed_scripts) {
+        Write-Warning "Skipping tests and code linting for decompress.ps1 files because it didn't change"
+        $excludes += 'Decompress'
+    }
+
+    if ($commitMessage -match '!manifests') {
         Write-Warning "Skipping manifest validation per commit flag '!manifests'"
         $excludes += 'Manifests'
     }
 
     $changed_manifests = (Get-GitChangedFile -Include '*.json' -Commit $commit)
-    if(!$changed_manifests) {
+    if (!$changed_manifests) {
         Write-Warning "Skipping tests and validation for manifest files because they didn't change"
         $excludes += 'Manifests'
     }
 
-    if($excludes.Length -gt 0) {
+    if ($excludes.Length -gt 0) {
         $splat.ExcludeTag = $excludes
     }
 }
@@ -53,6 +59,6 @@ $result = Invoke-Pester @splat
 
 (New-Object Net.WebClient).UploadFile("https://ci.appveyor.com/api/testresults/nunit/$($env:APPVEYOR_JOB_ID)", $resultsXml)
 
-if($result.FailedCount -gt 0) {
+if ($result.FailedCount -gt 0) {
     exit $result.FailedCount
 }
diff --git a/test/fixtures/decompress/TestCases.zip b/test/fixtures/decompress/TestCases.zip
new file mode 100644
index 0000000000..f5a7227088
Binary files /dev/null and b/test/fixtures/decompress/TestCases.zip differ
diff --git a/test/fixtures/unzip_old/small.zip b/test/fixtures/unzip_old/small.zip
deleted file mode 100644
index 09e3f8bd9a..0000000000
Binary files a/test/fixtures/unzip_old/small.zip and /dev/null differ
diff --git a/test/fixtures/unzip_old/zerobyte.zip b/test/fixtures/unzip_old/zerobyte.zip
deleted file mode 100644
index e69de29bb2..0000000000