### 🧪 Add tests for network configuration switching

[El-swaggerito]

Overview
Verify that the SDK correctly switches between testnet, mainnet, and custom RPC endpoints.

Requirements

• Test default testnet config
• Test mainnet config
• Test custom endpoint config

Acceptance Criteria

• Correct RPC endpoint is selected
• Invalid configs fail clearly
• All config branches are tested

Labels: testing, network

[soomtochukwu]

@soomtochukwu has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hello, you can trust me to take care of this ASAP

ℹ️ Repo Maintainers: To accept this application, review their application or assign @soomtochukwu to this issue.