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pester-migration

Migrates PowerShell Pester test suites across major versions v3 through v6.

38.5k|4.9k|Updated Jun 11, 2025
Search Tags:#upgrade#Mocking#CI-CD#pester#powerShell#test migration#Unit testing
One-click install
npx skills add https://github.com/github/awesome-copilot --skill pester-migration
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: pester-migration
Source: https://github.com/github/awesome-copilot/tree/main/skills/pester-migration
Command: npx skills add https://github.com/github/awesome-copilot --skill pester-migration

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Upgrading Pester test suites across major versions breaks existing tests in non-obvious ways — the v4→v5 Discovery/Run split silently nulls variables, mock assertions get renamed or removed, and legacy Invoke-Pester parameters stop working. This Skill provides version-detection heuristics, a step-by-step migration workflow, and symptom-to-fix tables so suites get green again without changing what they assert.

Core Features & Use Cases

  • Version Detection Heuristics: Identify which Pester version a suite was written for from syntax patterns like Should Be, $MyInvocation.MyCommand.Path, or Assert-MockCalled.
  • Per-Jump Migration Guides: Detailed references for v3→v4 (syntax renames), v4→v5 (Discovery/Run restructuring, BeforeAll, $PSScriptRoot, -ForEach), and v5→v6 (breaking changes like removed mock fall-through and empty -ForEach throwing).
  • Invoke-Pester Parameter Mapping: Convert legacy v4 parameters (-Script, -OutputFile, -CodeCoverage) to the New-PesterConfiguration object model.
  • Use Case: A CI pipeline fails after bumping Pester from 4 to 5 because setup code at the top of *.Tests.ps1 files runs during Discovery instead of Run. The Skill walks you through moving imports into BeforeAll, converting foreach-generated tests to -ForEach, and re-running until the suite matches its baseline.

Quick Start

Migrate my Pester test suite in the tests folder from version 4 to version 5 and fix any failures.

Frequently Asked Questions about pester-migration

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I migrate Pester tests from v4 to v5?▼

Move file imports into BeforeAll using $PSScriptRoot instead of $MyInvocation.MyCommand.Path, move test-generating code into BeforeDiscovery, and convert foreach-generated tests to -ForEach. Then convert Invoke-Pester legacy parameters to New-PesterConfiguration and re-run with -Output Diagnostic.

How do I upgrade Pester tests from v3 to v4?▼

Convert bareword assertions like Should Be to the dashed form Should -Be, rename Should Contain to Should -FileContentMatch, and rename Assert-VerifiableMocks to Assert-VerifiableMock. An AST-based converter script can automate the dash insertion, but review the diff and preserve file encoding.

Why are my Pester v5 variables null after migrating from v4?▼

Pester v5 splits runs into Discovery and Run phases, so code at the top of a test file or loose in a Describe body executes during Discovery and its variables are unavailable during Run. Move setup into BeforeAll and data generation into BeforeDiscovery.

What replaced Assert-MockCalled in Pester 6?▼

Assert-MockCalled was replaced by Should -Invoke, and Assert-VerifiableMock by Should -InvokeVerifiable. Both old cmdlets were deprecated in v5 and removed entirely in v6, so rename them during migration.

Can I skip a Pester major version when migrating?▼

No, migrate one major version at a time — go v4 to v5, then v5 to v6. Each jump has a different character, and skipping versions makes it impossible to match failures to documented breaking changes.

Why does Pester 6 throw on empty -ForEach data?▼

Pester 6 throws when -ForEach or -TestCases receives null or an empty array to catch bugs where data failed to load in BeforeDiscovery. Add -AllowNullOrEmptyForEach to blocks where empty data is legitimately expected.

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