Summary

Critical testability blocker. Direct dependency on concrete Google API types makes unit testing impossible. All command tests require real API credentials.

Current State

• gmail.Client.Service is *gmail.Service (concrete)
• calendar.Client.Service is *calendar.Service (concrete)
• contacts.Client.Service is *people.Service (concrete)
• No way to inject mocks

Files:

• internal/gmail/client.go:28-32
• internal/calendar/client.go:25-26
• internal/contacts/client.go:22-23

Problems

1. Cannot swap implementations (mock, different versions)
2. Cannot add caching, rate limiting, or circuit breakers without touching all call sites
3. Tests require real Google services

Proposed Solution

Define interfaces for each service:

type GmailService interface {
    GetMessage(userID, messageID string) (*Message, error)
    SearchMessages(userID, query string, maxResults int64) ([]*Message, error)
    GetThread(userID, threadID string) (*Thread, error)
    // ...
}

Make Service field private, expose only through interface.

Priority

P0 - Critical for testability