Allow setting the notification topic ARN for ElastiCache clusters.

[thegedge]

I learned that setting an empty string for the ARN on modify is a no-op, so you have to set the status to "inactive". This was the one oddity in this change.

I manually tested various creation / update scenarios, but let me know if there's somewhere I can add some tests.

[apparentlymart]

I'm not too familiar with this ElastiCache feature, but this change looks reasonable to me having guessed what these fields probably mean.

Terraform plugins typically use acceptance tests rather than unit tests, since mocking away the target service wouldn't leave much to test. You can see the current set of acceptance tests in the resource_aws_elasticache_cluster_test.go file in the same directory, and run them using:

make testacc TEST=./builtin/providers/aws TESTARGS='-run=ElasticacheCluster'

This requires the usual AWS environment variables to be set for some AWS credentials where it can create resources for testing. Of course running these tests could cost you money, so the main Terraform README states that contributions are not required to run or write acceptance tests. They are certainly appreciated if you're willing, though.

[thegedge]

Given that the existing tests aren't comprehensive and also that we've been running this code for our own stacks (we do a custom build of terraform that merges in a bunch of feature branches we'd like) without any problems, I'd love to be able to merge this as-is.

[catsby]

Thanks @thegedge – I've opened #3674 to include a test for the new notification_topic_arn, so I'm going to close this one.

Thanks!

[thegedge]

Thanks for picking that up, @catsby! Your PR gives me a better idea of how to approach the acceptance tests in future PRs I may send your way 😄

[catsby]

Eagerly awaiting more PRs 😄

[ghost]

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