This PR adds comprehensive test coverage for the WealthsimplePosition struct, following the existing patterns established in TokenTests and WealthsimpleAccountTests. The implementation includes 24 new test cases that cover all code paths and error scenarios.

Key Changes

New Test File: WealthsimplePositionTests.swift

• 24 comprehensive test cases covering all public methods and error scenarios
• Success scenarios: Valid JSON parsing, multiple positions, date parameter handling
• Error scenarios: Network failures, JSON parsing errors, missing/invalid data, HTTP errors
• Edge cases: Various asset types (equity, currency, mutual funds), invalid dates, malformed JSON

Enhanced Mock Infrastructure

• Extended MockURLProtocol to support positions endpoint requests
• Added getPositionsRequestHandler for consistent mocking patterns
• Created helper methods for common test scenarios and data generation

WealthsimplePosition Improvements

• Added Equatable conformance to PositionError enum for proper test assertions
• Fixed SwiftLint violations including pattern matching and code style issues
• Maintained backward compatibility with all existing functionality

Test Coverage Details

The tests comprehensively cover:

• JSON Parsing: Valid position data, missing attributes, invalid data types
• Network Requests: Success responses, HTTP errors, network failures, wrong response types
• Error Handling: All PositionError cases including noDataReceived, httpError, invalidJson, invalidJsonType, missingResultParamenter, invalidResultParamenter, assetError
• Asset Types: Different asset types to ensure broad compatibility
• Date Handling: Both with and without date parameters in requests

All tests follow the established patterns in the codebase, use proper mocking without external network calls, and maintain the project's high code quality standards. SwiftLint warnings for file and class length have been appropriately suppressed as permitted by the issue requirements.

Fixes #260.

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