Label a one-package release with its version, not its last character

ci/get-next-package-version.Tests.ps1

@@ -0,0 +1,46 @@
+# Tests for ci/get-next-package-version.ps1, which labels a publish with the
+# highest version in the release plan.
+#
+# Each test copies the script to a throwaway folder beside a packages.ps1
+# whose release plan is the versions the test gives, so the test states the
+# plan it labels.
+
+Describe 'get-next-package-version.ps1' {
+    BeforeAll {
+        $script:Label = Join-Path $PSScriptRoot 'get-next-package-version.ps1'
+
+        function Get-Label([string[]]$Versions) {
+            $folder = Join-Path ([IO.Path]::GetTempPath()) `
+                ([Guid]::NewGuid().ToString())
+            $null = New-Item -ItemType Directory $folder
+            try {
+                Copy-Item $script:Label $folder
+                $list = ($Versions | ForEach-Object { "'$_'" }) -join ', '
+                Set-Content (Join-Path $folder 'packages.ps1') @"
+function Get-ReleasePlan(`$RepoPath) {
+    @(@($list) | ForEach-Object {
+        [pscustomobject]@{ Name = "package-`$_"; Version = `$_ }
+    })
+}
+"@
+                & (Join-Path $folder 'get-next-package-version.ps1') `
+                    -RepoName 'repository' -VariableName 'TestLabel'
+                return $global:TestLabel
+            } finally {
+                Remove-Item -Recurse -Force $folder
+            }
+        }
+    }
+
+    It 'labels a plan of one package with its whole version' {
+        Get-Label @('4.5.3') | Should -Be '4.5.3'
+    }
+
+    It 'labels a plan of several packages with the highest version' {
+        Get-Label @('4.5.3', '4.5.10', '4.5.9') | Should -Be '4.5.10'
+    }
+
+    It 'gives a valid version when nothing is released' {
+        Get-Label @() | Should -Be '4.5.0'
+    }
+}

ci/get-next-package-version.ps1

@@ -13,7 +13,7 @@ $ErrorActionPreference = "Stop"
 # build-package.ps1 and publish-package.ps1, all from the same release plan.
 $plan = @(Get-ReleasePlan $RepoName)
 if ($plan.Count -gt 0) {
-    $label = ($plan.Version | Sort-Object { [version]$_ })[-1]
+    $label = @($plan.Version | Sort-Object { [version]$_ })[-1]
 } else {
     # Nothing to release. Any valid version will do, because
     # package-update-required.ps1 stops the publish before it is used.