Add unit tests for the assert_event helper correctly failing when event topic does not match

[Chucks1093]

Summary

The assert_event test helper should fail with a clear message when the transaction result contains events but none match the expected topic. Unit tests should confirm the helper fails correctly on a topic mismatch and passes on a correct topic.

Scope

• Emit an event with topic buy and call assert_event with topic sell — assert the helper panics
• Emit an event with topic buy and call assert_event with topic buy — assert the helper passes
• Emit no events and call assert_event with any topic — assert the helper panics
• Assert the panic message on topic mismatch identifies the expected and actual topics

Acceptance Criteria

• Mismatch topic causes helper to panic
• Panic message identifies expected and actual topics
• No events causes helper to panic
• Matching topic passes without panic

ETA: 12 hours

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Coordinate on Telegram

[Godfrey-Delight]

@Godfrey-Delight has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi maintainer please assign

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[somotochukwu-dev]

@somotochukwu-dev has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi
Please assign this issue to me
Thanks

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[richardtanimu3]

@richardtanimu3 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this issues

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[chidii]

@chidii has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello Maintainer, I've reviewed this issue thoroughly and I'm well positioned to resolve it — experienced across the relevant stack and comfortable navigating the existing codebase. Ready to start right away.

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