---
name: pester-should-migration
description: 'Experimental (preview) Pester skill for migrating classic Should -Be (v5) assertion syntax to the new Should-* (v6) assertions (note the hyphen, no space), e.g. `Should -Be` -> `Should-Be`, `Should -Not -Be` -> `Should-NotBe`. Tracks Pester 6, which is still a release candidate, so this guidance may change; verified against Pester 6.0.0-rc2. Use when converting Pester v5 assertions to Pester v6 Should-* operators, modernizing a Pester test suite, or when a user asks to migrate, convert, or rewrite `Should -...` calls in .Tests.ps1 / PowerShell files.'
argument-hint: "File, folder, or test suite to migrate"
---
# Pester `Should -*` → `Should-*` Migration
Convert classic Pester v5 assertions (`Should -Be`, space then parameter) to the
new Pester v6 `Should-*` assertions (`Should-Be`, hyphen, no space).
> **Status: experimental / preview.** Verified against Pester 6.0.0-rc2. The classic
> `Should -Be` style still works in v6, so migrate incrementally and keep the suite green.
> **Companion skill.** This skill covers the *optional* move to the new `Should-*` operators.
> To upgrade a suite across major Pester versions (v3→v4→v5→v6 — the runtime, mocks, and config),
> use the separate **pester-migration** skill. In v6 the classic `Should -Be` keeps working, so
> adopting `Should-*` is independent of any version bump.
## When to Use
- Modernizing a Pester suite to the v6 `Should-*` assertions.
- A user asks to migrate / convert / rewrite `Should -...` calls.
- You want clearer, type-aware failure messages from the new assertions.
## Know This First
- **Both syntaxes work side by side in Pester v6.** Migration is optional and can
be done one test (or one file) at a time. Nothing breaks if you leave some classic.
- **Requires Pester v6+.** The `Should-*` commands do not exist in v5.
- **Negation is a separate command**, not a `-Not` switch: `Should -Not -Be` →
`Should-NotBe`. There is no `-Not` parameter on the new assertions.
- **The actual value still comes from the pipeline** (`$x | Should-Be 1`) or from
`-Actual` (`Should-Be -Actual $x -Expected 1`). `-Because` carries over unchanged.
- **Most renames are mechanical**, but several have behavior changes you must check
by hand — see [Gotchas](#step-3--check-the-behavioral-gotchas-do-not-skip).
## Procedure
### Step 1 — Find the classic assertions
Search the target for the classic space-separated syntax (the tell is `Should -`,
or `Should` followed by `-Not`):
```
Should - # any classic operator
Should -Not - # negated classic operator
Assert-MockCalled # also removed in v6 -> Should-Invoke
```
Limit the scope to PowerShell test files (`*.Tests.ps1`, `*.ps1`).
### Step 2 — Apply the mapping
Most-used conversions (full list in [references/assertion-map.md](references/assertion-map.md)):
| Classic (v5) | New (v6) |
|---|---|
| `$x \| Should -Be 1` | `$x \| Should-Be 1` |
| `$x \| Should -Not -Be 1` | `$x \| Should-NotBe 1` |
| `$x \| Should -BeExactly 'A'` | `$x \| Should-BeString 'A' -CaseSensitive` |
| `$x \| Should -BeGreaterOrEqual 2` | `$x \| Should-BeGreaterThanOrEqual 2` |
| `$x \| Should -BeLessOrEqual 2` | `$x \| Should-BeLessThanOrEqual 2` |
| `$x \| Should -BeLike 'a*'` | `$x \| Should-BeLikeString 'a*'` |
| `$x \| Should -Match 're'` | `$x \| Should-MatchString 're'` |
| `$x \| Should -BeOfType [int]` | `$x \| Should-HaveType ([int])` |
| `$x \| Should -BeNullOrEmpty` | depends — see gotchas (no single equivalent) |
| `$c \| Should -HaveCount 3` | `$c \| Should-BeCollection -Count 3` |
| `$c \| Should -Contain 2` | `$c \| Should-ContainCollection 2` |
| `{ ... } \| Should -Throw 'msg'` | `{ ... } \| Should-Throw -ExceptionMessage 'msg'` |
| `Should -Invoke Get-Thing` | `Should-Invoke Get-Thing` |
| `Should -InvokeVerifiable` | `Should-Invoke -Verifiable` |
### Step 3 — Check the behavioral gotchas (do NOT skip)
These do **not** translate by a plain rename. Read each before converting:
1. **Case sensitivity.** Classic `Should -Be` is case-insensitive on strings; so is
`Should-Be`. But classic `Should -BeExactly` (case-sensitive) has **no** plain
equivalent — use `Should-BeString -CaseSensitive`. (`Should-Be` is never
case-sensitive.) Same pattern for `BeLikeExactly` → `Should-BeLikeString -CaseSensitive`
and `MatchExactly` → `Should-MatchString -CaseSensitive`.
2. **Truthy vs. true.** Classic `Should -BeTrue` / `-BeFalse` accept any *truthy* /
*falsy* value (`1`, `'x'`, `0`, `''`, `$null`, `@()`). The new `Should-BeTrue` /
`Should-BeFalse` are **strict** (exactly `$true` / `$false`). To preserve the old
loose behavior use `Should-BeTruthy` / `Should-BeFalsy`. Only use the strict ones
when the value really is a boolean.
3. **`BeNullOrEmpty` has no single equivalent.** Pick by intent: `$null` →
`Should-BeNull`; empty string → `Should-BeEmptyString`; empty collection →
`Should-BeCollection -Count 0`; broad "falsy" → `Should-BeFalsy`. The negation
`Should -Not -BeNullOrEmpty` similarly splits into `Should-NotBeNull` /
`Should-NotBeEmptyString` / `Should-NotBeWhiteSpaceString`.
4. **Collections.** Classic `Should -Be` also compares arrays; the new `Should-Be` is
a *value* assertion and **errors** if `-Expected` is a collection ("You provided a
collection to the -Expected parameter"). Use `Should-BeCollection` to compare arrays.
`Should -Contain` (single-item membership) → `Should-ContainCollection`. The new
command also takes a **collection** of expected items and checks they are all present,
in the right order (`1, 2, 3 | Should-ContainCollection @(1, 2)`). For exact,
whole-collection equality use `Should-BeCollection` instead.
5. **Pipeline unwrapping.** The pipeline unwraps input: a value assertion sees `@(1)`
as `1` and `@()` as `$null`, and a typed collection (`[int[]]`) is re-collected as
`[object[]]`. When the exact value or concrete collection type matters (e.g.
`Should-HaveType`), pass it with `-Actual` instead of piping.
6. **No `Should-*` equivalent.** `Should -Exist` and the `Should -FileContentMatch*`
family have no new counterpart. Either keep the classic assertion, or rewrite with
PowerShell: `Test-Path $p | Should-BeTrue`, `(Get-Content $p -Raw) | Should-MatchString 're'`.
7. **`Should -BeIn` direction.** No `Should-BeIn`. Reverse the operands:
`$value | Should -BeIn $collection` → `$collection | Should-ContainCollection $value`
(note the actual/expected swap), or keep the classic form.
### Step 4 — Verify
Run the suite and confirm it's still green — the new messages differ, but passes
must stay passes:
```powershell
Invoke-Pester -Path ./tests
```
If a converted assertion newly fails, re-check the gotchas above (most often #2
truthy/falsy, #3 null-or-empty, or #4 collections).
### Step 5 — (Optional) Enforce the new style
Once a suite is fully migrated, switch off the classic syntax so it can't creep back:
```powershell
$config = New-PesterConfiguration
$config.Should.DisableV5 = $true
```
With this set, any remaining `Should -Be` throws and points at the `Should-Be` form.
## Output
Summarize what changed: files touched, count of assertions converted, any classic
assertions intentionally left (e.g. `Should -Exist`), and any conversions that need
a human decision (truthy/falsy, null-or-empty, collection semantics).
## Reference
- [references/assertion-map.md](references/assertion-map.md) — full operator-by-operator
table with before/after examples and workarounds.
- Live command reference: `https://pester.dev/docs/commands/Should-Be` (swap in any
`Should-*` name) for exact parameters and examples.
- Concepts: `https://pester.dev/docs/assertions/should-command` (value vs. collection
assertions, pipeline vs. `-Actual`).
- v5→v6 upgrade guide: `https://pester.dev/docs/migrations/v5-to-v6`.