How to Fix jest.mock() Issues When Testing with @ databricks/sql

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Understanding the Problem

Analyzing the Situation

Here's a brief overview of your code structure:

A test file includes a mock response from a JSON file along with a handler function that connects to Databricks using the @ databricks/sql package.

The main goal is to simulate the behavior of external calls and ensure your tests focus on the logic rather than dependencies.

Your Initial Test Setup

In your setup, you attempted the following mock configuration:

[[See Video to Reveal this Text or Code Snippet]]

The behavior should mock the connection and session handling from @ databricks/sql, but it wasn't working as expected. The main culprit was the lack of proper Promise resolutions in your mocked functions.

Solution: Modifying the Mock

The solution is to ensure that the mocked functions return Promises, matching the behavior of real asynchronous implementations. Below are the modified mock configurations that successfully resolved the issue:

Updated Mock Code

Here's the corrected code for mocking the @ databricks/sql package:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Changes

Return Promises: Functions such as connect, openSession, executeStatement, and fetchAll now explicitly return Promises. This is critical for ensuring that synchronous waits behave correctly and that your test doesn't time out due to unresolved Promises.

Final Test Execution

After making these adjustments, your tests should run successfully. You can expect the following console outputs, indicating that your mocks are being correctly invoked:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Mocking dependencies in unit tests can sometimes be tricky, especially when dealing with asynchronous code. By ensuring your mocks return the expected Promise structures, you can avoid common pitfalls such as code being executed from the original modules instead of your mocks.