Changes Made:
Added new test cases in callbacks test suite.
Used mock responses from getMockResponseStreaming.
Improved test coverage for streaming responses.

Test for onData callback: Ensures onData is called with non-empty data chunks.
Test for onError callback: Ensures onError is triggered with a GoogleGenerativeAIError when the response contains an error.
Test for onEnd callback: Ensures onEnd is correctly called with the final processed data.
Test for all callbacks: Verifies that onData and onEnd are properly called in a long response

🔹 Additional Notes:
The test suite improvements enhance the reliability of the streaming functionality by validating the correct execution of all callback functions.

all Test Cases are Passes