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Exercise 2: Testing the Translation Workflow

During this exercise, you will

  • Run a unit test provided for the translateTerm Activity
  • Develop and run your own unit test for the translateTerm Activity
  • Write assertions for a Workflow test
  • Uncover, diagnose, and fix a bug in the Workflow Definition
  • Observe the time-skipping feature in the Workflow test environment

Make your changes to the code in the practice subdirectory (look for TODO comments that will guide you to where you should make changes to the code). If you need a hint or want to verify your changes, look at the complete version in the solution subdirectory.

Setup

You'll need two terminal windows for this exercise.

  1. In all terminals, change to the exercises/testing-code/practice directory.
  2. In one terminal, run npm install to install dependencies.

Part A: Running a Test

We have provided a unit test for the translateTerm Activity to get you started. This test verifies that the Activity correctly translates the term "Hello" to German. Take a moment to study the test, which you'll find in the src/mocha/activities.test.ts file. Since the test runs the Activity, which in turn calls the microservice to do the translation, you'll begin by starting that.

  1. In one terminal, run npm run service
  2. In another terminal, run the npm test command to execute the provided test

Part B: Write and Run Another Test for the Activity

Now it's time to develop and run your own unit test, this time verifying that the Activity correctly supports the translation of a different word in a different language.

  1. Edit the src/mocha/activities.test.ts file
  2. Copy the successfully translates "Hello" to German test, renaming the new test as successfully translates "Goodbye" to Latvian
  3. Change the term for the input from Hello to Goodbye
  4. Change the language code for the input from de (German) to lv (Latvian)
  5. Assert that translation returned by the Activity is Ardievu

Part C: Test the Activity with Invalid Input

In addition to verifying that your code behaves correctly when used as you intended, it is sometimes also helpful to verify its behavior with unexpected input. The following example does this, testing that the Activity returns the appropriate error when called with an invalid language code.

  it('fails to translate with bad language code', async () => {
    const env = new MockActivityEnvironment();
    const input = {
      term:         "Hello",
      languageCode: "xq",
    };
    try {
      await env.run(activities.translateTerm, input);
      assert.fail('Expected error was not thrown');
    } catch (err: any) {
      console.log(err.message)
      assert(err.message.includes("HTTP Error 400: Unknown language code \"xq\""));
    }
  });

Take a moment to study this code, and then continue with the following steps:

  1. Edit the src/mocha/activites.test.ts file
  2. Copy the entire "fails to translate with bad language code" function provided above and paste it at the bottom of the src/mocha/activities.test.ts file
  3. Save the changes
  4. Run npm test again to run this new test, in addition to the others

Part D: Test a Workflow Definition

  1. Edit the src/mocha/workflows.test.ts file
  2. Remove the first and last line of the file to uncomment the test.
  3. Add assertions for the following conditions
    • The helloMessage field in the result is Bonjour, Pierre
    • The goodbyeMessage field in the result is Au revoir, Pierre
  4. Save your changes
  5. Run npm test. This will fail, due to a bug in the Workflow Definition.
  6. Find and fix the bug in the Workflow Definition
  7. Run the npm test command again to verify that you fixed the bug

There are two things to note about this test.

First, the test completes in under a second, even though the Workflow Definition contains a sleep call that adds a 10-second delay to the Workflow Execution. This is because of the time-skipping feature provided by the test environment.

Second, the test defines a Worker that registers your Activities, meaning that the Activity Definitions are executed as part of this Workflow test. As you learned, you can test your Workflow Definition in isolation from the Activity implementations by using mocks. The optional exercise that follows provides an opportunity to try this for yourself.

This is the end of the exercise.

(Optional) Using Mock Activities in a Workflow Test

If you have time and would like an additional challenge, continue with the following steps.

  1. Make a copy of the existing Workflow Test by running cp src/mocha/workflows.test.ts src/mocha/workflows-mocks.test.ts
  2. Edit the src/mocha/workflows-mocks.test.ts file
  3. Add an import for sinon with import sinon from 'sinon';
  4. Add an import for the Translation Activity input and output import { TranslationActivityInput, TranslationActivityOutput } from '../shared';
  5. Rename the test function to it('successfully completes French translation with a mocked call', async () => {
  6. Make the following changes between where the object representing workflow input is defined and where the Worker is defined:
    • Create and populate an instance of the TranslationActivityInput object to represent input passed to the Activity when translating the greeting. Name it helloInput.
    • Create and populate an instance of the TranslationActivityOutput object to represent output returned by the Activity when translating the greeting. Name it helloOutput.
    • Repeat the above two steps, this time creating objects for the goodbye message. Switch the names from hello to goodbye.
    • Use Sinon to create a mock that represents the TranslateTerm Activity, which will return the output object you created when called with the input object you created: const translateTermMock = sinon.stub();
    • Add the following two lines to return mock results for the translations: translateTermMock.withArgs(helloInput).resolves(helloOutput); translateTermMock.withArgs(goodbyeInput).resolves(goodbyeOutput);
  7. For the Worker, modify the registered Activities so it uses your mock: activities: { translateTerm: translateTermMock },
  8. Save your changes
  9. Run npm test to run the tests