DerivingVia machinery for mocking AWS interactions in tests

This module assumes your specs run in a custom transformer that can provide a reader environment. If you define HasMatchers for that environment, you can then derive MonadAWS for this transformer via MockAWS.

For a more explicit alternative, see Control.Monad.AWS.MockT.

Example:

Assuming you have some implementation you wanted to test:

getBucketsByPrefix :: (MonadIO m, MonadAWS) m => Text -> m [Bucket]
getBucketsByPrefix p = do
  resp <- send newListBuckets
  pure
   $ maybe [] (filter matchesPrefix)
   $ resp ^. listBucketsResponse_buckets
 where
  matchesPrefix b = p isPrefixOf toText (b ^. bucket_name)

And assuming you've set up your example monad with MonadAWS via MockAWS, you can now test it without talking to AWS:

describe "getBucketsByPrefix" $ do
  it "works" $ do
    now <- getCurrentTime

    let
      bucketA = newBucket now "a-bucket"
      bucketB = newBucket now "b-bucket"
      bucketC = newBucket now "c-bucket"
      buckets = [bucketA, bucketB, bucketC]
      matcher =
        SendMatcher (== newListBuckets)
         $ Right
         $ newListBucketsResponse 200
         & listBucketsResponse_buckets ?~ buckets

    withMatcher matcher $ do
      buckets <- getBucketsByPrefix "b-"
      buckets shouldBe [bucketB]