grafana

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Table of Contents

General
Guidelines
Structure
Examples

General

A test for component dir/a.ts resides in dir/specs/a.test.ts.
A test for React component dir/a.tsx resides in dir/a.test.tsx
Tests are unit tests and should not instantiate the whole app.
Learn from other, recently written tests.
Tests are written in Jest.

Guidelines

Pure functions are easier to test than object members. Try writing the code accordingly.
When instantiating classes try to provide the absolute minimum in the constructor.
Keep the tests as framework-agnostic as possible, e.g.,:
- remove angular-specific mocks
- replace ctx.$q.when() with Promise.resolve(). Use the q package to handle cases where .finally() is a problem: q.when().

Structure

Execute the function that's being tested in the test block, not in setup or beforeEach.
Make clear what's being tested:

import MyComponent, { processData } from '../MyComponent';

describe('MyComponent', () => {
  // Component-wide tests
  it('should do something', () => {
  });

  // Component-member tests
  describe('modifyComponent()', () => {
    it('should modify the component like this', () => {
      const component = new MyComponent();

      let options = {};
      component.modifyComponent(options);
      expect(component.x).toBe(..);

      options = { foo: 42 };
      component.modifyComponent(options);
      expect(component.x).toBe(..);
    });
  });
});

// Pure functions
describe('processData()', () => {
  it('should transform input to output', () => {
  });
});

Examples

Setups stubs and passes them as parameters into the constructor:

https://github.com/grafana/grafana/blob/master/public/app/features/dashboard/specs/change_tracker.jest.ts

These tests use the simple backend_srv stub(https://github.com/grafana/grafana/blob/master/public/test/mocks/backend_srv.ts):

This test uses a Jest mock to test if an event has been emitted which can be useful sometimes. Most of the time you should use a stub rather than a mock but this is a case where you have to use a mock:

https://github.com/grafana/grafana/blob/master/public/app/core/specs/search_results.jest.ts