Checking the exchange's API

1. Have a Unix machine with Ruby 2.7.1 and Bundler.
2. Run bundle check || bundle update

1. Run cucumber
2. To see the webSockets messsages being exchanged etc, run DEBUG=yes cucumber

I know how to test REST APIs.

Not so much about webSockets solutions.

Let's have a test of a webSockets API with Cucumber.

I never used webSockets before, so I went with whatever tools popped first in my DuckDuckGo searches.

I got Websockets Client for Ruby from Bernard Potocki as the base interface.

I have no idea how to use that client in a manner that would allow me to use the "monkeypatching" described by Michael Wynholds.

I can still trivially leverage Cuke's expressive powers to describe the checks I perform on the communications between my test client and Kraken, by having the whole exchange as a When, storing all received messages in memory and performing all the Then checks on the memory recording.

The scope I finished this evening is:

• subscribe to ticker channels for 2 pairs
• accumulate no more than max ticks per pair, then unsubscribe
• once all pairs were unsubscribed from, close the webSockets connection
• examine record of the webSockets messages received from Kraken
  • online status - raise if not online since no other action will succeed
  • confirmation of subscribing and unsubscribing from the ticker channels
    • if max ticks are high, timeout is low and there is little trading on the pair, the connection can expire before confirmation of unsubscription was received
      • when it happens, the last step of the Gherkin will be pending
      • this is an actual test of the test, proving that it can do more than just pass if we parameterise it just right
      • to make it always pass, it would suffice to change how closing of connection on timeout works:
        • send unsubscribe messages for all pairs
        • set a new timeout
        • let the default logic work (close connection when all unsubscription messages arrived)
        • raise on new timeout
  • presence of at least the one initial tick for each pair
  • if more than one tick was received for pair, I check that the volume over last 24h was always increasing