Assert-MockCalled vs Assert-VerifiableMocks in Pester

Question

What makes Assert-VerifiableMocks different from Assert-MockCalled in Pester? I've been reading

• https://github.com/pester/Pester/wiki/Assert-VerifiableMocks
• https://github.com/pester/Pester/wiki/Assert-MockCalled

but still wonder: are the following sections of code equivalent and interchangeable?

Using Assert-MockCalled:

Mock Invoke-MongoCommmand {}
Set-TargetResource -UserName $test_username -Ensure "Absent"
Assert-MockCalled Invoke-MongoCommand -ParameterFilter {
    $Expression -eq "db.dropUser('$test_username')"
}

Using Assert-VerifiableMocks:

Mock Invoke-MongoCommand {} -Verifiable -ParameterFilter {
    $Expression -eq "db.dropUser('$test_username')"
}
Set-TargetResource -UserName $test_username -Ensure "Absent"
Assert-VerifiableMocks

Answer 1

The functionality of Assert-VerifiableMocks isn't a subset of Assert-MockCalled it's a disjoint set. With Assert-VerifiableMocks you can verify many mocks are called at the same time, but as already mentioned you cannot verify any mocks are not called. I have an example below to more fully explain these two differences testing an example 'Get-ValueSum'.

If you notice with Assert-verifiableMocks you can verify that the test has called all the expected mocks in a single assert.

Assert-Verifiable Sample

describe 'Assert-MockCalled vs Assert-VerifiableMocks in Pester' {
    function Get-Value1{ 1}
    function Get-Value2{ 2}
    function Get-Value3{ 3}
    
    # Should never be called by Get-ValueSum
    function Get-Value4{ 4}

    # Sums Value 1, 2 & 3, but 4 only if $include4 is specified
    function Get-ValueSum
    {
        param([switch] $inclued4 )
        if($inclued4)
        {
            return (Get-Value1) + (Get-Value2) + (Get-Value3) + (Get-Value4)
        }
        else
        {
            return (Get-Value1) + (Get-Value2) + (Get-Value3)
        }
    }

    context 'assert verifiable' {
        # Mark the first 3 mocks as verifiable 
        # because they should not be called 
        mock -CommandName Get-Value1 -MockWith { 2} -Verifiable
        mock -CommandName Get-Value2 -MockWith { 3} -Verifiable
        mock -CommandName Get-Value3 -MockWith { 4} -Verifiable
        # Add this so we can verify it is not called
        mock -CommandName Get-Value4 -MockWith { 99} 
        
        $result = Get-ValueSum

        it 'Should call the 3 expected value calls' {
            Assert-VerifiableMock
        }

        it 'should not call get-value 4' {
            Assert-MockCalled -CommandName Get-Value4 -Times 0
        }

        it 'should have gotten a sum of 9' {
            $result | should be 9
        }
        # add test for #$include4
    }
}

Assert-MockCalled Sample

describe 'Assert-MockCalled vs Assert-VerifiableMocks in Pester' {
    function Get-Value1{ 1}
    function Get-Value2{ 2}
    function Get-Value3{ 3}
    
    # Should never be called by Get-ValueSum
    function Get-Value4{ 4}

    # Sums Value 1, 2 & 3, but 4 only if $include4 is specified
    function Get-ValueSum
    {
        param([switch] $inclued4 )
        if($inclued4)
        {
            return (Get-Value1) + (Get-Value2) + (Get-Value3) + (Get-Value4)
        }
        else
        {
            return (Get-Value1) + (Get-Value2) + (Get-Value3)
        }
    }

    context 'assert mock called method' {
        # Add all mocks so we can verify 
        # if they were called or not individually
        mock -CommandName Get-Value1 -MockWith { 3} 
        mock -CommandName Get-Value2 -MockWith { 4} 
        mock -CommandName Get-Value3 -MockWith { 5} 
        mock -CommandName Get-Value4 -MockWith { 99} 

        $result = Get-ValueSum

        it 'Should call the 3 expected value calls' {
            Assert-MockCalled -CommandName Get-Value1 -Times 1
            Assert-MockCalled -CommandName Get-Value2 -Times 1
            Assert-MockCalled -CommandName Get-Value3 -Times 1
        }

        it 'should not call get-value 4' {
            Assert-MockCalled -CommandName Get-Value4 -Times 0
        }

        it 'should have gotten a sum of 12' {
            $result | should be 12
        }
        # add test for #$include4
    }
}