Implement Test Coverage for Gemini Provider

[Furisto]

Overview

The Gemini provider (`gemini.go`) is fully implemented with streaming, tool calling, and JSON schema conversion. However, there are no test files for this provider.

Current State

• ✅ Provider implementation complete with streaming support
• ✅ Tool calling fully integrated
• ✅ JSON schema conversion for Gemini API format
• ✅ Message transformation implemented
• ✅ Model definitions included (gemini-2.5-pro, gemini-2.5-flash, gemini-2.5-flash-lite)
• ❌ No test coverage

What Needs to be Done

Implement comprehensive unit tests for the Gemini provider to ensure reliability and catch regressions.

Test Coverage Requirements

1. Basic Invocation Tests

   • Test successful model invocation with valid inputs
   • Verify correct message formatting and transformation
   • Validate response structure and content

2. Streaming Tests

   • Test streaming callback functionality
   • Verify chunks are properly accumulated
   • Test handling of empty/incomplete streams
   • Test tool call streaming

3. Tool Calling Tests

   • Test tool transformation to Gemini format
   • Verify tool calling integration
   • Test handling of multiple tool calls
   • Test function response handling

4. Error Handling Tests

   • Missing or empty API key
   • Missing required fields (model, system prompt, messages)
   • Invalid message types
   • API errors and network failures
   • Invalid model profiles

5. Message Transformation Tests

   • User messages with text content
   • Model messages with text and tool calls
   • Tool result messages
   • Mixed message types in conversation history

6. JSON Schema Conversion Tests

   • Test conversion of JSON schema to Gemini schema format
   • Test property type conversions (string, number, boolean, array, object)
   • Test nested object handling
   • Test enum value handling
   • Test required fields

Files to Modify

• `backend/model/gemini.go` - Create new test file

References

• Implementation: `backend/model/gemini.go`
• Provider interface: `backend/model/provider.go`

[BenjaminGoehry]

Hey @Furisto
I can write the tests for gemini.go if you’re open to contributions. Happy to start with a PR for the basic invocation tests.
Let me know!