Fix tests

[yaacovCR]

graphql 1.1.0 only adds listeners after first call to next(), see apollographql/graphql-subscriptions#148.

• NA: If this PR is a new feature, reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• NA: Update CHANGELOG.md with your change. Include a description of your change, link to PR (always) and issue (if applicable). Add your CHANGELOG entry under vNEXT. Do not create a new version number for your change yourself.

[apollo-cla]

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[yaacovCR]

Closing in favor of #1206