Add regression test for event emission count on successful buy

[aniokedianne]

Summary
Existing buy event tests assert the payload fields but not how many events are emitted. A regression test that counts emitted events on a successful buy confirms exactly one buy event is emitted and no extra events are produced as a side effect.

Scope

• add a regression test that performs a successful buy and collects all emitted events
• assert exactly one buy event is emitted
• assert no unexpected event types appear alongside the buy event

Acceptance Criteria

• exactly one buy event is emitted on a successful buy
• no extra or unexpected events are emitted
• the test fails if event count changes

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[Emelie-Dev]

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[Johnpii1]

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Hello Sir,

I recently came across your project and I’m very interested in contributing to the team.

I have experience working with React to build responsive and user-friendly interfaces, and I also have a solid understanding of smart contracts and blockchain fundamentals. I enjoy writing clean, scalable code and focusing on improving overall user experience.

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Thank you for your time and consideration. I look forward to hearing from you.

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[Johnsmichael150]

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