Use Unicode Control Pictures for special characters in assertions

src/functions/assertions/Be.ps1

@@ -312,7 +312,7 @@ function Expand-SpecialCharacters {
         [AllowEmptyString()]
         [string[]]$InputObject)
     process {
-        $InputObject -replace "`n", "\n" -replace "`r", "\r" -replace "`t", "\t" -replace "`0", "\0" -replace "`b", "\b"
+        [Pester.Formatter]::EscapeControlChars($InputObject)
     }
 }
 

tst/functions/assert/String/Should-BeString.Tests.ps1

@@ -155,14 +155,8 @@ But was:  'abc'
 
     It "Shows expanded whitespace characters in diff" {
         $err = { "abc`ndef" | Should-BeString "abc`r`ndef" } | Verify-AssertionFailed
-        $err.Exception.Message | Verify-Equal (@'
-Expected strings to be the same, but they were different.
-Expected length: 8
-Actual length:   7
-Strings differ at index 3.
-Expected: 'abc\r\ndef'
-But was:  'abc\ndef'
-          ----^
-'@ -replace "`r`n", "`n")
+        $cr = [char]0x240D
+        $lf = [char]0x240A
+        $err.Exception.Message | Verify-Equal ("Expected strings to be the same, but they were different.`nExpected length: 8`nActual length:   7`nStrings differ at index 3.`nExpected: 'abc${cr}${lf}def'`nBut was:  'abc${lf}def'`n          ---^" -replace "`r`n", "`n")
     }
 }

tst/functions/assertions/Be.Tests.ps1

@@ -151,15 +151,15 @@ InPesterModuleScope {
         }
 
         It "Replaces non-printable characters correctly" {
-            ShouldBeFailureMessage "`n`r`b`0`tx" "`n`r`b`0`ty" | Verify-Equal "Expected strings to be the same, but they were different.`nString lengths are both 6.`nStrings differ at index 5.`nExpected: '\n\r\b\0\ty'`nBut was:  '\n\r\b\0\tx'`n           ----------^"
+            ShouldBeFailureMessage "`n`r`b`0`tx" "`n`r`b`0`ty" | Verify-Equal "Expected strings to be the same, but they were different.`nString lengths are both 6.`nStrings differ at index 5.`nExpected: '$(([char]0x240A))$(([char]0x240D))$(([char]0x2408))$(([char]0x2400))$(([char]0x2409))y'`nBut was:  '$(([char]0x240A))$(([char]0x240D))$(([char]0x2408))$(([char]0x2400))$(([char]0x2409))x'`n           -----^"
         }
 
         It "The arrow points to the correct position when non-printable characters are replaced before the difference" {
-            ShouldBeFailureMessage "123`n456" "123`n789" | Verify-Equal "Expected strings to be the same, but they were different.`nString lengths are both 7.`nStrings differ at index 4.`nExpected: '123\n789'`nBut was:  '123\n456'`n           -----^"
+            ShouldBeFailureMessage "123`n456" "123`n789" | Verify-Equal "Expected strings to be the same, but they were different.`nString lengths are both 7.`nStrings differ at index 4.`nExpected: '123$(([char]0x240A))789'`nBut was:  '123$(([char]0x240A))456'`n           ----^"
         }
 
         It "The arrow points to the correct position when non-printable characters are replaced after the difference" {
-            ShouldBeFailureMessage "abcd`n123" "abc!`n123" | Verify-Equal "Expected strings to be the same, but they were different.`nString lengths are both 8.`nStrings differ at index 3.`nExpected: 'abc!\n123'`nBut was:  'abcd\n123'`n           ---^"
+            ShouldBeFailureMessage "abcd`n123" "abc!`n123" | Verify-Equal "Expected strings to be the same, but they were different.`nString lengths are both 8.`nStrings differ at index 3.`nExpected: 'abc!$(([char]0x240A))123'`nBut was:  'abcd$(([char]0x240A))123'`n           ---^"
         }
     }
 }