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When integration testing or running your systems within a deployed environment, we recommend that you use a dedicated Basis Theory tenant for each test environment that is separate from your production tenant. For example, if you maintain a separate Development, QA, Staging, and Production environment for your systems, we recommend that you mirror this setup by creating 4 separate tenants in Basis Theory. This can help you to isolate test data from production data and allow you to more securely lock down access to production API keys.

Testing Reactors

Reactor formula code is simply an ES module that exports a default function. This can be tested like any JavaScript code or ES module using the tooling of your choice. Internally at Basis Theory, we unit and integration test our reactor formulas using Jest to ensure the JavaScript code itself works as expected.

Unit Testing

For unit testing, we use Jest mocks to mock either SDK methods if we use a third party SDK in the reactor, or to mock usages of an http client (e.g. axios, node-fetch).

const fetch = require('node-fetch');

// this is a fake piece of data we expect the destination service to return
const fakeTransactionId = chance.string();

// here we mock the json response returned by node-fetch
jest.mock('node-fetch', () =>
status: 200,
json: jest
// this mock should return a "real" response based on what your mocked service normally returns
.mockImplementation(() => Promise.resolve({ transaction_id: fakeTransactionId }))

describe('Example reactor unit test', () => {
const reactorFormula = require('./reactor');

it('should call third party service', async () => {
// this is the request we will pass into the reactor formula
const reactorRequest = {
configuration: {
THIRD_PARTY_API_KEY: chance.string()
args: {
card_number: chance.string()

// we expect the third party service to be called by our reactor with this payload
const expectedRequestToThirdParty = {
payment_method: {
credit_card: {
number: reactorRequest.args.card_number

const reactorResponse = await reactorFormula(reactorRequest);

method: 'POST',
headers: {
'Content-Type': 'application/json',
// our third party service accepts the API key in an X-API-KEY header
'X-API-KEY': reactorRequest.configuration.THIRD_PARTY_API_KEY
body: JSON.stringify(expectedRequestToThirdParty)

// we expect our reactor to return the transactionId returned by the third party service
raw: {
transactionId: fakeTransactionId

Integration Testing

For integration testing, we ensure the reactor code actually works against the destination services that the reactor integrates with. As an example, the following snippet shows a sample reactor integration test:

const reactorFormula = require('./reactor'); // this file exports our reactor function as an ES module
const { AuthenticationError } = require('@basis-theory/basis-theory-reactor-formulas-sdk-js');

describe('Example reactor integration test', () => {
it('should return expected response', async () => {
const actualResponse = await reactorFormula({
configuration: {
// this is a real api key for an external service called by our reactor
args: {
// requests to the reactor will contain a token, which will be detokenized
// into plaintext before it reaches our reactor code
// here we test with a fake plaintext card number
card_number: '4242424242424242'

// assert on whatever you expect the reactor to return, in our case we expect a transactionId to be returned

it('should throw an AuthenticationError when using an invalid API key', async () => {
await expect(
configuration: {
// pass in a fake api key that will be rejected by the third party service
THIRD_PARTY_API_KEY: chance.string()
args: {
card_number: '4242424242424242'
).rejects.toThrow(new AuthenticationError().message);

End-to-End Testing

End-to-end tests against reactors running in Basis Theory can provide further confidence that your reactors work in a deployed environment. These tests require a bit more setup and should sit at the top of your testing pyramid, so we encourage you to first focus on unit and integration tests before attempting to write automated end-to-end tests. If you do choose to write end-to-end tests, here are some tips to keep in mind:

  • The reactor under test must be provisioned either just-in-time during the test using a management application's API key, or manually provisioned ahead of time and referenced by id in the tests. Either solution requires some configuration to be passed into your tests.
  • Invoking your reactor under test will require a private application's API key with token:use permission.
  • If your reactor expects to be called with detokenization expressions in the request, the tokens referenced in your test requests must be pre-created by your test code. This will require access to either a public or private application's API key with token:create permission.

Testing Techniques

Mocking at the Network Level

Mocking network calls is useful within a category of testing that we refer to as Acceptance Testing. While the terminology differs throughout the software industry, we use this term to refer to black box testing of a system component to ensure it meets business requirements (i.e. acceptance criteria). With this type of test, you typically strive to mock external dependencies, especially network calls to external systems.

There are many tools available to facilitate mocking network calls, such as Wiremock (our preferred tool) or Mock Service Worker. If you're interested in learning more, check out our series of blog posts diving deep into our testing philosophy at Basis Theory.

Mocking at the Unit Level

We recommend that you generally adhere to good design principles and strive to loosely couple your application code from external dependencies, including integration points with Basis Theory. This can be accomplished by using inversion of control and dependency injection within your codebase whenever possible.

We also offer official SDKs in many languages, which provide standard interfaces for interacting with the Basis Theory API. This makes it easy to mock methods on these interfaces within your unit tests. While the specifics of how to structure your code and mock dependencies within unit tests differ across languages and frameworks, you have all the tools available to write loosely-coupled and well-tested code.

Test Data

Card Numbers

The card and card_number token types accept any Luhn-valid card numbers and are not restricted to a particular set of card numbers, even for tenants only used for testing purposes. However, if you exchange card tokens with any external systems using reactors or the proxy, those systems may have their own test card requirements that you should follow to ensure the integration works as expected.

While we do not limit you to a particular set of card numbers, for your convenience we list below some sample test card numbers that pass Luhn-validation and resolve to a valid card brand.

Card NumberCVCBrand
4242424242424242Any 3 digitsVisa
5555555555554444Any 3 digitsMastercard
378282246310005Any 4 digitsAmerican Express
6011111111111117Any 3 digitsDiscover
3056930009020004Any 3 digitsDiners Club
3566002020360505Any 3 digitsJCB
6200000000000005Any 3 digitsUnion Pay