Added subscription tests and unsubscribe function

[trickstival]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
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• Yes
• No

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The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
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[posva]

Thank you this!
Can we add another test that check that multiple calls to the unsubscribe function does nothing? This test would also allow you to verify the problem I mentioned in the comment

[posva]

What is the _subscriptions for? I would rather not directly expose them Eduardo San Martin Morote

…

On 22 Dec 2019, at 15:33, Patrick ***@***.***> wrote:  @posva Done — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.

[trickstival]

What is the _subscriptions for? I would rather not directly expose them Eduardo San Martin Morote
…
On 22 Dec 2019, at 15:33, Patrick @.***> wrote:  @posva Done — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.

You're right. At first glance it was the way I found to test if the subscriptions were right. Now I changed it to use spies instead.

[posva]

thanks!