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Assert‐MockCalled

Andrew Sears edited this page Dec 13, 2019 · 5 revisions

Checks if a Mocked command has been called a certain number of times and throws an exception if it has not. If the call history of the mocked command does not match the parameters passed to Assert-MockCalled, Assert-MockCalled will throw an exception.

Parameters

CommandName

The mocked command whose call history should be checked.

ModuleName

The module where the mock being checked was injected. This is optional, and must match the ModuleName that was used when setting up the Mock.

Times

The number of times that the mock must be called to avoid an exception from throwing.

Exactly

If this switch is present, the number specified in Times must match exactly the number of times the mock has been called. Otherwise it must match "at least" the number of times specified. If the value passed to the Times parameter is zero, the Exactly switch is implied.

ParameterFilter

An optional filter to qualify which calls should be counted. Only those calls to the mock whose parameterscause this filter to return true will be counted.

Scope

An optional parameter specifying the Pester scope in which to check for calls to the mocked command. By default, Assert-MockCalled will find all calls to the mocked command in the current Context block (if present), or the current Describe block (if there is no active Context.) Valid values are Describe, Context and It. If you use a scope of Describe or Context, the command will identify all calls to the mocked command in the current Describe / Context block, as well as all child scopes of that block.

Example 1

C:\PS>Mock Set-Content {}

{... Some Code ...}

C:\PS>Assert-MockCalled Set-Content

This will throw an exception and cause the test to fail if Set-Content is not called in Some Code.

Example 2

C:\PS>Mock Set-Content -ParameterFilter {$path.StartsWith("$env:temp\")}

{... Some Code ...}

C:\PS>Assert-MockCalled Set-Content 2 -ParameterFilter { $path -eq "$env:temp\test.txt" }

This will throw an exception if some code calls Set-Content on $path=$env:temp\test.txt less than 2 times

Example 3

C:\PS>Mock Set-Content {}

{... Some Code ...}

C:\PS>Assert-MockCalled Set-Content 0

This will throw an exception if some code calls Set-Content at all

Example 4

C:\PS>Mock Set-Content {}

{... Some Code ...}

C:\PS>Assert-MockCalled Set-Content -Exactly 2

This will throw an exception if some code does not call Set-Content Exactly two times.

Example 5

Describe 'Assert-MockCalled Scope behavior' {
    Mock Set-Content { }

    It 'Calls Set-Content at least once in the It block' {
        {... Some Code ...}
        Assert-MockCalled Set-Content -Exactly 0 -Scope It
    }
}

Checks for calls only within the current It block.

Example 6

Describe 'Describe' {
    Mock -ModuleName SomeModule Set-Content { }

    {... Some Code ...}

    It 'Calls Set-Content at least once in the Describe block' {
        Assert-MockCalled -ModuleName SomeModule Set-Content
    }
}

Checks for calls to the mock within the SomeModule module. Note that both the Mockand Assert-MockCalled commands use the same module name.

Additional Notes

The parameter filter passed to Assert-MockCalled does not necessarily have to match the parameter filter (if any) which was used to create the Mock. Assert-MockCalled will find any entry in the command history which matches its parameter filter, regardless of how the Mock was created. However, if any calls to the mocked command are made which did not match any mock's parameter filter (resulting in the original command being executed instead of a mock), these calls to the original command are not tracked in the call history. In other words, Assert-MockCalled can only be used to check for calls to the mocked implementation, not to the original.

Parameter names can be aliased and thus available via an unexpected variable. Within the -ParameterFilter block one can Write-Host all available parameter variable names and values:

Assert-MockCalled CommandName -Times 1 -ParameterFilter {
  Write-Host (Get-Variable | Select-Object -Property Name,Value)
}            
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