Pester testing framework basics in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Pester test block?

Consider this Pester test script:

Describe 'Math tests' {
  It 'adds numbers correctly' {
    (2 + 3) | Should -Be 5
  }
  It 'multiplies numbers correctly' {
    (4 * 2) | Should -Be 8
  }
}

What will Pester report after running this script?

PowerShell

Describe 'Math tests' {
  It 'adds numbers correctly' {
    (2 + 3) | Should -Be 5
  }
  It 'multiplies numbers correctly' {
    (4 * 2) | Should -Be 8
  }
}

A 2 tests, 2 passed, 0 failed

B 2 tests, 1 passed, 1 failed

C 1 test, 1 passed, 0 failed

D 0 tests run

💡 Hint

Both math operations are correct, so both tests should pass.

The script defines two tests, both with correct assertions. Pester will report 2 tests run, both passed.

📝 Syntax

intermediate

Identify the syntax error in this Pester test

Look at this Pester test code:

Describe 'String tests' {
  It 'checks string length' {
    'hello'.Length | Should -Be 5
  }
  It 'checks string content' 
    'hello' | Should -Be 'hello'
}

Which option correctly describes the syntax error?

PowerShell

Describe 'String tests' {
  It 'checks string length' {
    'hello'.Length | Should -Be 5
  }
  It 'checks string content' 
    'hello' | Should -Be 'hello'
}

A Should command is misspelled

B Missing closing brace '}' after first It block

C Missing opening brace '{' after second It block

D Describe block is missing parentheses

💡 Hint

Each It block must have braces enclosing its code.

The second It block lacks the opening brace '{', causing a syntax error.

🔧 Debug

advanced

Why does this Pester test fail unexpectedly?

Given this Pester test:

$value = 10
Describe 'Value tests' {
  It 'checks if value is greater than 5' {
    $value -gt 5 | Should -Be $true
  }
  It 'checks if value is less than 20' {
    $value -lt 20 | Should -Be $false
  }
}

Why does the second test fail?

PowerShell

$value = 10
Describe 'Value tests' {
  It 'checks if value is greater than 5' {
    $value -gt 5 | Should -Be $true
  }
  It 'checks if value is less than 20' {
    $value -lt 20 | Should -Be $false
  }
}

A The variable $value is not accessible inside the Describe block

B The second test expects $false but the condition is true

C The Should command is used incorrectly with -Be

D The first test modifies $value causing the second to fail

💡 Hint

Check the logic of the condition and the expected value in the second test.

The condition '$value -lt 20' is true because 10 is less than 20, but the test expects $false, so it fails.

🚀 Application

advanced

How to test a function output with Pester?

You have this PowerShell function:

function Get-Greeting {
  param([string]$Name)
  "Hello, $Name!"
}

Which Pester test block correctly verifies that calling Get-Greeting with 'Alice' returns 'Hello, Alice!'?

PowerShell

function Get-Greeting {
  param([string]$Name)
  "Hello, $Name!"
}

Describe 'Get-Greeting function' {
  It 'returns correct greeting for Alice' {
    # Fill in the test here
  }
}

A Get-Greeting -Name 'Alice' | Should -Be 'Hello, Alice!'

B "Hello, Alice!" | Should -Be (Get-Greeting -Name 'Alice')

C Get-Greeting 'Alice' | Should -Be 'Hello, Alice!'

D Get-Greeting -Name Alice | Should -Be 'Hello Alice!'

💡 Hint

Use the function call on the left side of the Should command and the expected string on the right.

Option A correctly calls the function with named parameter and compares output to expected string.

🧠 Conceptual

expert

What is the purpose of the 'BeforeAll' block in Pester?

In Pester testing, what does the 'BeforeAll' block do compared to 'BeforeEach'?

A 'BeforeAll' and 'BeforeEach' are interchangeable and run before each test

B 'BeforeAll' runs before every It block; 'BeforeEach' runs once before all tests

C 'BeforeAll' runs after all tests; 'BeforeEach' runs before all tests

D 'BeforeAll' runs once before all tests in a Describe block; 'BeforeEach' runs before every It block

💡 Hint

Think about setup code that should run once versus before every test.

'BeforeAll' is used to run setup code once before any tests run in the Describe block. 'BeforeEach' runs before each individual test.