How to pass array values from the terraform to the Helm chart values.yaml file using terraform-provider?

Question

I am using terraform helm provider to pass values to helm values.yaml. I have a json file of field 'test_groups': ['TEST_GROUP_1', 'TEST_GROUP_2']. I am using join function to parse this json and facing an issue with it

set {
  name = "my_test_groups"
  value = "{${join(",", each.value.test_groups)}}"
}

My goal is to send this array values to values.yaml file and I am unsure if join is right function to do so. Any suggestions are appreciated

values.yaml

test_groups: ["TEST_GROUP_1", "TEST_GROUP_2"]
OR
test_groups: 
  - TEST_GROUP_1
  - TEST_GROUP_2