<!--
title: Proper mocking techniques
domain: observability
topic: Testing
language: TSX
source: grafana/grafana
updated: 2025-07-04
url: https://awesomereviewers.com/reviewers/grafana-proper-mocking-techniques/
-->

Use appropriate mocking approaches for different dependencies in tests to ensure accurate test results and prevent false positives. Different types of dependencies require different mocking strategies:

1. For browser APIs not implemented in JSDOM (like `window.open`):
```javascript
// Define and mock the property before using it
// @ts-expect-error global.open should return a Window, but is not implemented in js-dom.
const openSpy = jest.spyOn(global, 'open').mockReturnValue(true);
```

2. For utility functions like logging, prefer individual method mocks with cleanup:
```javascript
beforeEach(() => {
  jest.spyOn(log, 'error').mockImplementation(() => {});
  jest.spyOn(log, 'warning').mockImplementation(() => {});
  jest.spyOn(log, 'debug').mockImplementation(() => {});
});

afterEach(() => {
  jest.resetAllMocks();
});
```

3. For module dependencies, use dedicated mocks rather than actual imports:
```javascript
// Instead of using setupDataSources which imports actual modules:
const dsServer = new MockDataSourceSrv(datasources) as unknown as DataSourceSrv;
```

Using precise mocking strategies improves test reliability, prevents unexpected behavior from external dependencies, and ensures tests validate exactly what you intend to test.