[Bug] Terratest plan not working as expected

[michaelamattes]

Description

See PR telekom-mms/terraform-azurerm-cdn#17. The terraform plan test should be fail before merge the configuration fix. But the test finished successfully.
It should be proved if the terraform plan command runs correctly for the examples.

Reproduction steps

Add failure within examples or main.tf so that a terraform plan fails, see code bevore telekom-mms/terraform-azurerm-cdn#17

Current Behavior

terraform plan for full_main.tf finshed successfully

Expected Behavior

terraform plan for full_main.tf should be failed - becaus code was not correct

Additional information

No response