Google Apps Script:
Writing tests

How to:

While Google Apps Script does not have a built-in testing framework like some other programming environments, you can still write and run tests by leveraging simple GAS functions or integrating external testing libraries such as QUnit. Here’s a basic example using a simple GAS function to test another function in your script:

function add(a, b) {
  return a + b;
}

function testAdd() {
  var result = add(2, 3);
  if (result !== 5) {
    throw new Error("Test failed: add(2, 3) should be 5, but was " + result);
  } else {
    Logger.log("Test passed!");
  }
}

Running testAdd() will log “Test passed!” if the add function works correctly, or throw an error if it doesn’t. For a more sophisticated approach, integrating QUnit with Google Apps Script involves a few more steps but offers a powerful testing environment. A sample QUnit test setup looks like this:

1. Include the QUnit library in your project.
2. Create a test HTML file for running the QUnit tests.
3. Write test cases using QUnit’s syntax.

Here’s an example using QUnit:

// Include QUnit by linking to it in an HTML file used to run your tests

QUnit.test("Testing add function", function (assert) {
  var result = add(2, 3);
  assert.equal(result, 5, "add(2, 3) should return 5");
});

To see the results, open the HTML file within the GAS Script Editor or deploy it as a web app.

Deep Dive

Historically, testing in Google Apps Script has been somewhat overlooked, likely due to the platform’s origins and primary use cases focusing on quick, small-scale automation tasks rather than large applications. As such, GAS doesn’t offer the same robust testing frameworks and tools found in more traditional programming environments. However, the community has adapted by incorporating open-source libraries and leveraging Google’s existing tools creatively.

Using libraries like QUnit represents a significant step forward but comes with its own set of challenges, such as setting up a suitable testing environment and learning an additional syntax. However, for those invested in building more complex and reliable applications with GAS, the effort is worthwhile.

Alternatives like using simple GAS functions for testing offer ease of use and integration with the GAS environment without additional dependencies but lack comprehensive testing features and the ability to easily scale as your project grows. Tools such as clasp (the Google Apps Script Command Line Interface) can facilitate more advanced workflows, including testing, by allowing developers to code in their preferred IDE, introducing room for integrating with external testing frameworks more seamlessly.

In conclusion, while GAS might not have native support for sophisticated testing out of the box, its flexibility and the community’s innovative approaches provide viable pathways to ensure your scripts are robust, reliable, and ready for any task.