How to use "File Should Contain" rule about poshspec HOT 4 CLOSED

PS C:\projects> .\test.ps1
Describing Files
 [+] File 'test.txt' Should Exist 478ms
 [-] File 'test.txt' Should Not Exist 217ms
   Expected: C:\projects\test.txt to not exist, but it was found
   1: 'C:\projects\test.txt' | Should Not Exist
   at <ScriptBlock>, <No file>: line 1
   at <ScriptBlock>, C:\Program Files\WindowsPowerShell\Modules\Poshspec\2.2.1\Private\Invoke-PoshspecExpression.ps1: line 13
 [+] File 'test.txt' Should Contain 'hello' 176ms
 [-] File 'test.txt' Should Contain 'other' 75ms
   Expected: file C:\projects\test.txt to contain {other}
   1: 'C:\projects\test.txt' | Should Contain 'other'
   at <ScriptBlock>, <No file>: line 1
   at <ScriptBlock>, C:\Program Files\WindowsPowerShell\Modules\Poshspec\2.2.1\Private\Invoke-PoshspecExpression.ps1: line 13
PS C:\projects> get-module

ModuleType Version    Name                                ExportedCommands                                                             
---------- -------    ----                                ----------------                                                             
Binary     1.0.0.0    CimCmdlets                          {Export-BinaryMiLog, Get-CimAssociatedInstance, Get-CimClass, Get-CimInsta...
Manifest   3.1.0.0    Microsoft.PowerShell.Management     {Add-Computer, Add-Content, Checkpoint-Computer, Clear-Content...}           
Manifest   3.0.0.0    Microsoft.PowerShell.Security       {ConvertFrom-SecureString, ConvertTo-SecureString, Get-Acl, Get-Authentico...
Manifest   3.1.0.0    Microsoft.PowerShell.Utility        {Add-Member, Add-Type, Clear-Variable, Compare-Object...}                    
Manifest   3.0.0.0    Microsoft.WSMan.Management          {Connect-WSMan, Disable-WSManCredSSP, Disconnect-WSMan, Enable-WSManCredSS...
Binary     1.0.0.1    PackageManagement                   {Find-Package, Find-PackageProvider, Get-Package, Get-PackageProvider...}    
Script     3.4.0      Pester                              {AfterAll, AfterEach, Assert-MockCalled, Assert-VerifiableMocks...}          
Script     2.2.1      Poshspec                            {AppPool, AuditPolicy, CimObject, DnsHost...}                                
Script     1.0.0.1    PowerShellGet                       {Find-Command, Find-DscResource, Find-Module, Find-RoleCapability...}        
Script     1.2        PSReadline                          {Get-PSReadlineKeyHandler, Get-PSReadlineOption, Remove-PSReadlineKeyHandl...