Variable validation blocks in Terraform - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a variable validation block in Terraform?

A variable validation block checks if the input value for a variable meets certain rules before applying the configuration. It helps catch errors early by enforcing constraints.

beginner

How do you define a validation block inside a Terraform variable?

Inside the variable block, you add a validation block with a condition expression and an error message. For example:<br>

variable "age" {<br>  type = number<br>  validation {<br>    condition     = age >= 18<br>    error_message = "Age must be 18 or older."<br>  }<br>}

beginner

What happens if a variable value does not meet the validation condition?

Terraform stops the plan or apply process and shows the error message defined in the validation block. This prevents invalid configurations from being deployed.

intermediate

Can validation blocks use complex expressions?

Yes, validation conditions can use any valid Terraform expression, including functions, comparisons, and logical operators to create complex rules.

intermediate

Why is using variable validation blocks considered a best practice?

They improve reliability by catching invalid inputs early, reduce debugging time, and make configurations easier to understand and maintain.

What keyword starts a validation block inside a Terraform variable?

A validation

B check

C assert

D verify

The correct keyword to define a validation block inside a variable is 'validation'.

What must a validation block always include?

A description and default

B type and default

C condition and error_message

D condition and default

A validation block requires a 'condition' expression and an 'error_message' to show if the condition fails.

If a variable fails validation, what does Terraform do?

A Ignores the error and continues

B Stops and shows the error message

C Uses the default value automatically

D Logs a warning but applies anyway

Terraform stops the process and shows the error message to prevent invalid inputs.

Can you use functions inside a validation condition?

A No, only simple comparisons are allowed

B Only string functions are allowed

C Only arithmetic functions are allowed

D Yes, any valid Terraform expression is allowed

Validation conditions can use any valid Terraform expression, including functions.

Which of these is a good reason to use variable validation blocks?

A To catch invalid inputs early

B To speed up Terraform apply

C To automatically fix errors

D To reduce variable declarations

Validation blocks help catch invalid inputs early, improving reliability.

Explain how to create a variable validation block in Terraform and what it does.

Think about how you check if a value is allowed before using it.

Why should you use variable validation blocks in your Terraform configurations?

Consider how catching mistakes early helps in real life.