Unit Testing Custom Actions

Unit tests help prevent regressions in custom action functionality. The createTemplateAction function that is the core of a custom action can be difficult to mock. There are helper methods that can assist.

Mocking the Context

The handler property of the createTemplateAction input object expects a context. You can create a mock context using the code below:

import { createMockActionContext } from '@backstage/plugin-scaffolder-node-test-utils';

const mockContext = createMockActionContext({
  input: { repoUrl: 'dev.azure.com?repo=repo&owner=owner&organization=org' },
});

await action.handler(mockContext);

expect(mockContext.output).toHaveBeenCalledWith(
  'remoteUrl',
  'https://dev.azure.com/organization/project/_git/repo',
);

Mocking a Workspace within the Context object

One thing to be aware about: if you would like to call createMockActionContext inside it, you have to provide a workspacePath. By default, createMockActionContext uses import { createMockDirectory } from '@backstage/backend-test-utils'; to create it for you. You can use the code below to customize the workspacePath without using the default workspace of the createMockActionContext function.

describe('github:autolinks:create', async () => {
  const workspacePath = createMockDirectory().resolve('workspace');
  // ...

  it('should call the githubApis for creating alphanumeric autolink reference', async () => {
    // ...
    await action.handler(
      createMockActionContext({
        input: {
          repoUrl: 'github.com?repo=repo&owner=owner',
          keyPrefix: 'TICKET-',
          urlTemplate: 'https://example.com/TICKET?query=<num>',
        },
        workspacePath,
      }),
    );
    //...
  });
});

Mocking a Config Core Service

If your custom Action requires the Config Core Service within execution of the handler(ctx) such as the custom action below, mocking the context object can be done by building a mockContext with the ConfigReader function within the @backstage/config package.

// custom-action.ts
import { Config } from '@backstage/config';

export const customActionRequiringConfigCoreService = (config: Config) => {
  const fieldRequiringValueFromConfig = config.getString('app.service.url');
  return createTemplateAction({
    ...
    async handler(ctx) {
      // Some code requiring the config const
      ctx.logger.info(fieldRequiringValueFromConfig);
    }
  })
}

// custom-action.test.ts
import { ConfigReader } from '@backstage/config';
import { customActionRequiringConfigCoreService } from './custom-action.ts';
...
const mockConfig = new ConfigReader({
  app: {
    service: {
      url: 'https://api.service.io/graphql',
      apiKeyId: '123',
      apiKeySecret: '123abc',
    },
  },
});
...
const action = customActionRequiringConfigCoreService(mockConfig);
await action.handler({
  ...mockContext
})

Mocking a Cache Core Service

Similar to the Mocking a Config Core Service section above, if your custom action expects a Cache Core Service Object as part of the function input, you can mock it out with the following:

import { CacheService } from '@backstage/backend-plugin-api';

const mockCacheServiceMethods = {
  get: jest.fn(),
  set: jest.fn(),
  delete: jest.fn(),
};

const mockCacheService = mockCacheServiceMethods as unknown as CacheService;

const action = customActionRequiringCacheCoreService(mockCacheService);
...