Static checks

Built in

Format

Enforces style rules for your configurations.

terraform fmt -check # checks if formatter would make chances

terraform fmt # applies those changes

Validate

Checks that configuration are valid.

Terraform init is required to use validate. If not working with a remote backend, terraform init -backend=false can be used.

terraform validate

Plan

Looking at the resulting Terraform plan can help catch bugs.

terraform plan

Custom Validation Rules

Enforce conditions on variables to prevent misuse

variable "short_variable" {
  type = string

  validation {
    condition = length(var.short_variable) < 4
    error_message = "The short_variable value must be less than 4 characters!"
  }
}

External

There are many 3rd party tools which can check Terraform configurations for potential issues and/or suggest best practices: