You have created a custom variable definition file testing.tfvars. How will you use it for provisioning infrastructure?

`-var-state-file` is not a valid Terraform CLI option for specifying a variable definition file.

The command `terraform plan` is for creating an execution plan, not applying infrastructure, and the file extension `tfvar` is a typo; it should be `tfvars`.

The correct command to use a custom variable definition file like `testing.tfvars` for provisioning infrastructure is `terraform apply -var-file="testing.tfvars"`. The `-var-file` flag instructs Terraform to load variable values from the specified file.

This command is syntactically incorrect as it's missing the hyphen before `var-file`, which is required for CLI flags.