PesterExampleUnexpectedThrowing.ps1

function Get-Something
{
    param
    (
        [Parameter()]
        [System.Boolean]
        $MockError
    )
}

function Test-Something
{
    param
    (
        [Parameter()]
        [System.Boolean]
        $MockError
    )

    Get-Something -MockError $MockError

    return $true
}

<#
    Calling the function that is under test in the Context-block.
    Neither It-block will run since we are mocking a fault here to
    illustrate a function that is throwing an unexpected error in
    the code path.
#>
Describe 'Something' {
    Context 'When this happens' {
        BeforeAll {
            Mock -CommandName Get-Something -MockWith {
                if ($MockError)
                {
                    throw 'Get-Something error'
                }
                else
                {
                    Write-Verbose -Message 'Get-Something' -Verbose
                }
            }
        }

        $result = Test-Something -MockError $true

        It 'Should do this in first code path' {
            $result | Should -Be $true

            Assert-MockCalled -CommandName Get-Something
        }

        It 'Should do this in second code path' {
            $result | Should -Be $true

            Assert-MockCalled -CommandName Get-Something
        }
    }
}

<#
    Calling the function that is under test in the first It-block only.
    We are mocking a fault here to illustrate a function that is throwing
    an unexpected error in the code path.
    Both It-blocks will run, but both will fail.
    First one because of it throwing an error instead of returning the
    correct value.
    Second one because the first one did not return the correct value.
#>
Describe 'Something' {
    Context 'When this happens' {
        BeforeAll {
            Mock -CommandName Get-Something -MockWith {
                if ($MockError)
                {
                    throw 'Get-Something error'
                }
                else
                {
                    Write-Verbose -Message 'Get-Something' -Verbose
                }
            }
        }

        It 'Should do this in first code path' {
            $result = Test-Something -MockError $true
            $result | Should -Be $true

            Assert-MockCalled -CommandName Get-Something
        }

        It 'Should do this in second code path' {
            $result | Should -Be $true

            Assert-MockCalled -CommandName Get-Something
        }
    }
}

<#
    Calling the function that is under test in each It-block.
    The first It-block will run, but the second It-block will fail since
    we are mocking a fault in the second code path to illustrate a function
    that is throwing an unexpected error.
#>
Describe 'Something' {
    Context 'When this happens' {
        BeforeAll {
            Mock -CommandName Get-Something -MockWith {
                if ($MockError)
                {
                    throw 'Get-Something error'
                }
                else
                {
                    Write-Verbose -Message 'Get-Something' -Verbose
                }
            }
        }

        It 'Should do this in first code path' {
            $result = Test-Something -MockError $false
            $result | Should -Be $true

            Assert-MockCalled -CommandName Get-Something
        }

        It 'Should do this in second code path' {
            $result = Test-Something -MockError $true
            $result | Should -Be $true

            Assert-MockCalled -CommandName Get-Something
        }
    }
}