Add regression test for the version prefix on release tags

The test asserts the tag a repository with VersionPrefix 'v' expects, and keeps an unprefixed repository covered. It fails against the current derivation, which builds the tag from the manifest's Major.Minor.Patch only.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

.github/actions/Publish-PSModule/tests/Publish-PSModule.Helpers.Tests.ps1

@@ -0,0 +1,94 @@
+[Diagnostics.CodeAnalysis.SuppressMessageAttribute(
+    'PSUseDeclaredVarsMoreThanAssignments', '',
+    Justification = 'Variables are assigned in BeforeAll and used inside It blocks.'
+)]
+[CmdletBinding()]
+param()
+
+BeforeAll {
+    Import-Module -Name 'PSModule' -Force
+    Import-Module -Name (Join-Path -Path $PSScriptRoot -ChildPath '../src/Publish-PSModule.Helpers.psm1') -Force
+}
+
+Describe 'Publish-PSModule.Helpers' {
+    Describe 'Get-ReleaseTag' {
+        Context 'Get-ReleaseTag - repository with a version prefix' {
+            It 'Get-ReleaseTag - prefixes a stable release tag with the configured prefix' {
+                Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' | Should -Be 'v1.1.10'
+            }
+
+            It 'Get-ReleaseTag - prefixes a stable release tag when the prerelease label is empty' {
+                Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease '' | Should -Be 'v1.1.10'
+            }
+
+            It 'Get-ReleaseTag - prefixes a prerelease tag with the configured prefix' {
+                Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease 'mybranch001' |
+                    Should -Be 'v1.1.10-mybranch001'
+            }
+
+            It 'Get-ReleaseTag - supports a multi-character prefix' {
+                Get-ReleaseTag -VersionPrefix 'release-v' -ModuleVersion '2.0.0' | Should -Be 'release-v2.0.0'
+            }
+        }
+
+        Context 'Get-ReleaseTag - repository without a version prefix' {
+            It 'Get-ReleaseTag - leaves a stable release tag unprefixed' {
+                Get-ReleaseTag -VersionPrefix '' -ModuleVersion '1.1.10' | Should -Be '1.1.10'
+            }
+
+            It 'Get-ReleaseTag - leaves a prerelease tag unprefixed' {
+                Get-ReleaseTag -VersionPrefix '' -ModuleVersion '1.1.10' -Prerelease 'mybranch001' |
+                    Should -Be '1.1.10-mybranch001'
+            }
+
+            It 'Get-ReleaseTag - treats an absent prefix as no prefix' {
+                Get-ReleaseTag -ModuleVersion '1.1.10' | Should -Be '1.1.10'
+            }
+
+            It 'Get-ReleaseTag - treats a null prefix as no prefix' {
+                Get-ReleaseTag -VersionPrefix $null -ModuleVersion '1.1.10' | Should -Be '1.1.10'
+            }
+        }
+
+        Context 'Get-ReleaseTag - input normalization' {
+            It 'Get-ReleaseTag - trims whitespace around the prefix' {
+                Get-ReleaseTag -VersionPrefix ' v ' -ModuleVersion '1.1.10' | Should -Be 'v1.1.10'
+            }
+
+            It 'Get-ReleaseTag - trims whitespace around the prerelease label' {
+                Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease ' mybranch001 ' |
+                    Should -Be 'v1.1.10-mybranch001'
+            }
+
+            It 'Get-ReleaseTag - treats a whitespace-only prerelease label as a stable release' {
+                Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease '   ' | Should -Be 'v1.1.10'
+            }
+
+            It 'Get-ReleaseTag - requires a module version' {
+                { Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '' } | Should -Throw
+            }
+        }
+
+        # Cleanup-PSModulePrereleases selects the releases to delete with
+        # `tagName -like "*$prereleaseName*" -and tagName -ne $publishedReleaseTag`, where the published tag is
+        # the value publish.ps1 exports as PSMODULE_PUBLISH_PSMODULE_CONTEXT_ReleaseTag. Both halves of that
+        # filter have to keep working once the tag carries a prefix.
+        Context 'Get-ReleaseTag - AutoCleanup tag matching contract' {
+            It 'Get-ReleaseTag - keeps the prerelease name inside a prefixed tag so cleanup still matches it' {
+                Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease 'mybranch001' |
+                    Should -BeLike '*mybranch*'
+            }
+
+            It 'Get-ReleaseTag - keeps the prerelease name inside an unprefixed tag so cleanup still matches it' {
+                Get-ReleaseTag -VersionPrefix '' -ModuleVersion '1.1.10' -Prerelease 'mybranch001' |
+                    Should -BeLike '*mybranch*'
+            }
+
+            It 'Get-ReleaseTag - produces the same tag twice so cleanup can exclude the published release' {
+                $first = Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease 'mybranch001'
+                $second = Get-ReleaseTag -VersionPrefix 'v' -ModuleVersion '1.1.10' -Prerelease 'mybranch001'
+                $first | Should -Be $second
+            }
+        }
+    }
+}