Getting Started

This document introduces Touca SDK for JavaScript through a simple example. If you are new to Touca, consider reading our general quickstart guide first.

Touca SDK for JavaScript is available as open-source on GitHub under the Apache-2.0 License. It is publicly available on NPM and can be pulled as a dependency using yarn or npm.

npm install @touca/node

In this tutorial, we will use Touca examples repository whose JavaScript examples already list this package as a dependency. Clone this repository to a local directory of your choice and proceed with building its JavaScript examples.

git clone git@github.com/trytouca/examples.git "<YOUR_LOCAL_DIRECTORY>"
cd "<YOUR_LOCAL_DIRECTORY>/js"
yarn install
yarn build

For our first example, let us write a Touca test for a software that checks whether a given number is prime. You can find a possible first implementation in ./js/01_node_minimal/is_prime.ts of the examples repository.

export function is_prime(input: number): boolean {
  for (let i = 2; i < input; i++) {
    if (input % i === 0) {
      return false;
    }
  }
  return 1 < input;
}

While this implementation is trivial, it represents our code under test with arbitrary complexity that may involve many nested function calls, interacting with systems and services. So while we can test the above code with unit tests, it may not be so easy to write and maintain unit tests for future versions of our software.

With Touca, we can test our software workflows regardless of their complexity. Here is an example Touca test for our is_prime software using the Touca SDK for JavaScript.

import { touca } from "@touca/node";
import { is_prime } from "./is_prime";

touca.workflow("is_prime_test", (testcase: string) => {
  const number = Number.parseInt(testcase);
  touca.check("is_prime_output", is_prime(number));
});

touca.run();

Typical Touca tests do not list the inputs that we use to test our workflow. We did not specify the expected output of our software either. This is unlike unit tests in which we hard-code our input values and their corresponding expected values.

With Touca, we would just define how to run our workflow under test for any given test case. We would capture values of interesting variables and runtime of important functions to describe the behavior and performance of our workflow for that test case. We would leave it to Touca to compare our description against that of a previous trusted version of our workflow and report the differences as our test cases are executed.

Let us run our Touca test, passing 13 as a sample input:

node 01_node_minimal/dist/is_prime_test.js --team tutorial --suite is_prime --revision 1.0 --offline --testcase 13

This command produces the following output.

Touca Test Framework
Suite: is_prime/1.0

 1.  PASS   13    (1 ms)

Tests:      1 passed, 1 total
Time:       0.12 s

✨   Ran all test suites.

The test framework passes 13 as the testcase parameter to our test workflow. We convert this testcase to a number and pass it to our code under test. We capture the actual value returned by our software as a Touca test result. This value is stored in its original data type, in a binary file ./results/is_prime/1.0/13/touca.bin.

Every time we make changes to our code under test, we can repeat this process with the same set of test cases. We could compare the generated binary files to check whether our code changes impact the overall behavior and performance of our software.

touca_cli compare --src=./results/is_prime/1.0/13/touca.bin --dst=./results/is_prime/1.0/13/touca.bin

But this method is only useful if we test our workflow under test with hundreds of test cases which would make dealing with result files very inconvenient. Fortunately, Touca has a server instance that can be self-hosted or cloud-hosted to manage and compare test results and report their differences.

If you have not already, create an account at app.touca.io. Once you make a new suite, the server shows an API Key and an API URL that you can use to submit test results.

export TOUCA_API_KEY="8073c34f-a48c-4e69-af9f-405b9943f8cc"
export TOUCA_API_URL="https://api.touca.io/@/tutorial/prime-test"
node 01_node_minimal/dist/is_prime_test.js --revision 1.0 --testcase 19 51 97

Touca Test Framework
Suite: prime-test/1.0

 1.  PASS   19    (109 ms)
 2.  PASS   51    (152 ms)
 3.  PASS   97    (127 ms)

Tests:      3 passed, 3 total
Time:       0.57 s

✨   Ran all test suites.

Now if we make changes to our workflow under test, we can rerun this test and rely on Touca to check if our changes affected the behavior or performance of our software.

node 01_node_minimal/dist/is_prime_test.js --revision 2.0

Touca Test Framework
Suite: prime-test/2.0

 1.  PASS   19    (109 ms)
 2.  PASS   51    (152 ms)
 3.  PASS   97    (127 ms)

Tests:      3 passed, 3 total
Time:       0.55 s

✨   Ran all test suites.

In our example, we captured the output of our workflow using touca.check. But unlike integration tests, we are not bound to the output of our workflow. We can capture any number of data points and from anywhere within our code. This is specially useful if our workflow has multiple stages. We can capture the output of each stage without publicly exposing its API. If the behavior of that stage changes in a future version of our code, we can leverage the captured output to find the root cause more easily.

In the next documents, we will learn how to use Touca SDK for JavaScript to test real-world software workflows.