const module = require('./module'); jest.spyOn(module, 'myFn').mockImplementation(() => 'val'); In Typescript, just import instead of require: import * as module from './module'; This has the advantage of making life easy to restore original functions and clear mocks. This comment has been minimized. Here is … Creating typed jest mocks. I have the following TypeScript object defined: // HttpClient.ts export type HttpResponse = Response & { data? I got jest installed, prefixed with .spec.jest.ts to separate jest test from karmas. Sign in to view. The project is written using typescript, which is nice. Of course this approach might be also used for other window variables like window.open or window.origin etc. The of() method transforms the result object into an observable. ./index.test.js (https://github.com/jmarceli/mock-window/blob/master/src/existing-variable/index.test.js) Please note that if you try to mock those variables directly(as in the second example e.g. First, we determine what response status code we want to test and the result data as well. You can just change it to this now (unless you had a custom setup where you have typescript files that you don’t want ts-jest to inspect). When I unit test my getters are setters for Typescript, I cannot find a way to spy on those getters and setters. This is one of those little Jest quirks I mentioned; jest… I wanted to write unit tests and I wanted the tests to run as fast as possible without any dependencies on a real Firestore instance — so I had to mock the Firestore calls. It took some time but I think I got it. All you gotta do now is mock a request and write your test. To fix that in your root TypeScript folder (in most instances that will be your src folder) create a module.d.ts file and add the following: declare namespace NodeJS { interface Global { fetch: jest.Mock } } This will set fetch on the Node globals type as a Jest mock function. That code needs to be tested, and it’s always a struggle to remember how to mock/stub or spy on Date.now/new Date with Jest.. Jest is very fast and easy to use I’ve been working with jest every day for the past month or so. And now it works ️. The way to define this in TS is Jest is a library for testing JavaScript code. The global spyOn() function returns a jasmine.Spy not a jest. It’s a bit annoying to setup because each line is a string. Let's take the jest.spyOn function, as an example. In this guide, we will focus on the jest.fn method, the simplest way to create a mock function. Click through for source There are situations where new Date() or Date.now is used in application code. Same approach works to replace any other library. I wanted to write unit tests and I wanted the tests to run … A few days ago I implemented a simple React component to upload files. I had to learn a few tricks as I went. Copy link Quote reply tiago-lp commented Jun 4, 2020. In … It is basically a set of cloud functions which interacts with a Firestore database, among other things. I tried jest.fn() and .mockImplementation(() => {}) and the By default jest.spyOn() does not override the implementation (this is the opposite of jasmine.spyOn). The simplest way to test a value is with exact equality. jest.spyOn(object, methodName) Creates a mock function similar to jest.fn but also tracks calls to object[methodName]. You have any example? Even with TypeScript in the mix, `ts-jest` makes testing React applications easy. Returns a Jest mock function. Photo by Ferenc Almasi on Unsplash I was working the other day on a firebase project. Then in your test where you need to mock a dependency you just need to. Then, let's create our tsconfig file: yarn tsc --init. (Run with npm test.) window.location.href = 'htt… Run npm run lint package-name (or tsc if no tslint.json is present). mock ('fs') const fs = require ('fs') // Mocked module const fs = require. I wanted to create a truth table in another file to pass into jest’s test.each() helper. And it works fine. Jest is used as a test runner (alternative: Mocha), but also as an assertion utility (alternative: Chai). Jest imports this file instead of isomorphic-fetch when running your code. (Compile and run.) Jest just picks up those files that are prefixed. Follow the advice from the readme. The goal is to test pieces of code in isolation without needing to know about the inner workings of their dependencies. Summary In TypeScript 3.9.x, module "re-export" is done using readonly accessor. expect.extend also supports async matchers. Snapshots live either alongside your tests, or embedded inline. Here is a short piece of sample code: This is the fourth entry in a short series about creating React/Redux applications with TypeScript. Note: By default, jest.spyOn also calls the spied method. The function works takes an object as a first parameter, and the method you wanna spy on … I wanted to create a truth table in another file to pass into jest’s test.each() helper. Jest is a library for testing JavaScript code. Jest has a decent mocking system but the creation and typing can be made a bit easier by using a helper library. Parcel requires zero configuration. Avoid common mistakes. Usually the first couple of letters are enough. Copy link Quote reply marco-souza commented Jul 20, 2020 • edited … The way to define this in TS is, Jest has some specific methods for helping to test promises and async code, You can expect a specific resolution or rejection using, If you had this setup in your jest.config.js file. Thanks to calling jest. mockImplementation (() => Promise. The project is written using typescript, which is nice. In the next test, we should expect an HTTP 400 code if the query isn’t complete. This comment has been minimized. In addition, it comes with utilities to spy, stub, and mock (asynchronous) functions. Jest ships as one unitary NPM package. I'm using yarn: yarn add jest ts-jest @types/jest -D. yarn add typeorm typescript pg. In case of variables which are globally available but are not provided by jsdom by default e.g. It breaks all tests written using jest.spyOn mocks. Active 2 years, 8 months ago. Here are five things I learned. The typing for this method is an array of sub arrays with the specific parameters defined. Typescript infers the string literals by looking up on the types used, either for the keyof operator and element access. Add or edit tests to reflect the change. So, today I'll show you how to configure your code to make tests with TypeORM and Jest. chai is an assertion library. Using Jest as an unit testing library provides many advantages: Unitary unit testing library for running and structuring tests. Ask Question Asked 4 years, 3 months ago. Jest is the default choice for TypeScript React projects. ... I’m using TypeScript, ... the mockFetch function uses the getGlobalObject to create a mock function calling the jest spyOn function. I'm working on rewriting my personal website using gatsby and TypeScript and decided to try out https://github.com/azz/jest-runner-tsc Powerful matchers to create simple to read tests. Use jest-dynamodb Preset Jest DynamoDB provides all required configuration to run your tests using DynamoDB. Note: mockRestore works only with mocks created by jest.spyOn. I have used jest-create-mock-instance for the past couple of months and it works really well. Mock dependency in jest with typescript, You can use type casting and your test.ts should look like this: ... Next, the mockFetch function uses the getGlobalObject to create a mock function calling the jest spyOn function.. With the mock function, we can mock its return value. The typing for this method is an array of sub arrays with the specific parameters defined. Include the name of the package modified. In this case, we are testing with the 200 status code and a dumb data object. Next, the mockFetch function uses the getGlobalObject to create a mock function calling the jest spyOn function.. With the mock function, we can mock its return value. If you are mocking an object method, you can use jest.spyOn. I wanted to set them up with the basics for Jest and TypeScript, so I created a small project: Since we wanted this session to be about testing, I added a small script to package.json: "scripts: { "test": "jest" },- it pays to spend some thought o… It works with projects using: Babel, TypeScript, Node, React, Angular, Vue and more! With the Global Setup/Teardown and Async Test Environment APIs, Jest can work smoothly with DynamoDB. How do I spyOn Typescript getters and setters? I was working the other day on a firebase project. It’s possible to require/import and expose the real module while using jest.mock. SpyInstance . We only have to create an object that has the properties status (containing the response status code) and JSON function (a promise that resolves with the result of parsing the body text as JSON). fixes #32866 Please fill in this template. The jest.fn method allows us to create a new mock function directly. Then, with jest.spyOn, we can mock the implementation of the get method of httpService. You can create a mock function with `jest.fn()`. ts-jest is a transform for jest which compiles typescript files. Note: In TypeScript, when using @types/jest for example, you can declare the new toBeWithinRange matcher like this: declare global { namespace jest { interface Matchers { toBeWithinRange(a: number, b: number): R; } } } Async Matchers. clearAllMocks jest. You may notice that jest.mock exists, but it doesn’t function as expected. Without knowing the actual API and requirements of Checkout as well as the /checkout endpoint, you can't really answer. In this code, .toBe(4)is the matcher. Thanks. Partial module mocking with jest.requireActual. When Jest runs, it tracks all the failing matchers so that it can print out nice error messages for you. Successfully Integrating Phaser 3 into your React/Redux App (Part 1), Create a Shopping App With Nativescript Vue, Firebase and Stripe, JavaScript Type Checking with Flow — Type Casting. Jest mock typescript. The keyof operator introduced in the PR can only see public methods Details see this Typescript issue microsoft/TypeScript#13543. In this example, I’m using TypeScript, but you can use the same strategy with just JavaScript as well. Refer to the official docs to get started. Finally, you can create your expects to validate your function request. By default jest.spyOn() does not override the implementation (this is the opposite of jasmine.spyOn). jest.requireActual(moduleName) Returns the actual module instead of a mock, bypassing all checks on whether the module should receive a mock implementation or not. We’re using the jest.spyOn() function, which has the following syntax: jest.spyOn(object, methodName) This function creates a mock function similar to jest.fn while tracking the calls to the object’s method (methodName). typescript jasmine getter-setter. We can now truly create our test using that auxiliary function. * has been released I've been running into a typing issue where spyOn can't seem to pick up the correct property out of the object that's being spied on. So, sorry about that. I live and work in Sydney, Australia enjoying the mountains and the ocean. requireActual ('fs') // Original module. The spyOn function returns a mock function.For a full list of its functionalities visit the documentation.Our test checks if the components call the get function from our mock after rendering and running it will result with a success. Use a meaningful title for the pull request. In this sample, we are looking to mock the fetch function, so this is what we are going to do. Fortunately, jest has functionality that solves the problem with the jest.spyOn (). With the mock function, we can mock its return value. I recently had a fun and instructive hands-on session with my colleagues to teach them unit testing with Jest/TypeScript and I wanted to share both the session and its preparation with you. So when your code says. It's an open source project maintained by Facebook, and it's especially well suited for React code testing, although not limited to that: it can test any JavaScript code. That's how we will use Jest to mock Axios. In this story, we would be using TypeScript for unit testing along with popular frameworks: Mocha/Chai, Jasmine or Jest. 9 ️ 1 1 aduth mentioned this issue Jan 16, 2020. If no implementation is given, the mock function will return `undefined` when invoked. If you don't want it to call through you have to mock the implementation: const callApi = jest. Snapshots. As we can see tested function uses globally available window.location variables.Those variables are provided by jsdom by default which let's us to mock them usingbuilt-in jest methods jest.spyOn(), .mockImplementation() and restore with .mockRestore(). Sometimes the mocks were inline, sometimes they were in variables, and sometimes they were imported and exported in magical ways from mysterious __mocks__ folders. jest.requireActual(moduleName) Returns the actual module instead of a mock, bypassing all checks on whether the module should receive a mock implementation or not. The interface for our validation service looks like this: iperson-validator.ts A few days ago I implemented a simple React component to upload files. I had to learn a few tricks as I went. mock ('axios') Jest replaces axios with our mock – both in the test and the component. Jest … Ok, let’s setup jest into your project. Click through for source. Jest is the default choice for TypeScript React projects. It’s possible to require/import and expose the real module while using jest.mock. This document will introduce some commonly used matchers. You typically won't do much with these expectation objects except call matchers on them. The preset is awesome and will find all your ts and tsx files. Instead, the object immediately gets evaluated. This is very helpful as the ORM library for your application. You can just add it if it’s not already there. I build and support happy teams that create high quality software for the web. After that, we can call our fetchAllRepositories function. Async matchers return a Promise so you will need to await the returned value. Using Jest as an unit testing library provides many advantages: Unitary unit testing library for running and structuring tests. You want your attendees to get up and running as quickly as possible, so you should prepare a small package to get them started that contains a small README (in markdown), some task file(s) and as little scaffolding as possible (packages.json, configs) to get them started. Simple Mocking of DynamoDb data mapper in the Jest code DynamoDB Data Mapper is an awslab’s open source project. use spyOn to create a spy around an existing object; use jasmine.createSpy to create a testable function; use jasmine.createSpyObj to create an object with a number of internal spy functions; It’s the latter that we’ll be using. How to mock a Fetch API request with Jest and TypeScript. In this example, it fetches a user’s repositories from GitHub. This is a bit of a trick question. restoreAllMocks Accessing the original module when using mocks . 1. And if you want to mock a whole module, you can use jest.mock. Typing a typescript array for jest test-each cases. "import createMockInstance from \"jest-create-mock-instance\";", " let myMockedDep: jest.Mocked;", " myMockedDep = createMockInstance(MyDependency)", " classUnderTest = new $1(myMockedDep);", " ])(\"is an expected response\", (input: string, expected: boolean) => {", " const result = classUnderTest.methodToTest(input);", " expect(result).toEqual(expected);", "A simple test template for starting a unit test". resetAllMocks jest. Jest uses "matchers" to let you test values in different ways. I was mocking, using async, upgrading versions and working in vscode. You can access the complete example here. But when can this be useful? Jest supports TypeScript, via Babel. They are readonly, so the normal jest.spyOn() fails, but they are also not getters, so the suggested jest.spyOn(object, 'method', 'get').mockReturnValue('mockedValue'); won't work here either. I prefer to use Typescript for my projects so this setup may be little bit different if you use plain javascript, but there will not be great difference. babel-jest is like ts-jest, but uses babel to transform files - handy if you have a project with some mixed typescript and javascript. Jest ships as one unitary NPM package. I extended @cpojer's suggestion to allow undoing the mock: TypeScript … Convoluted but how else is TypeScript supposed to know isomorphic-fetch is actually fetch-mock... PS: I'm assuming Jest because it's become the industry standard for JavaScript testing in the past few years. jest. In this case we're replacing the isomorphic-fetch library with a fetch-mock sandbox. Jest can be used in projects that use parcel-bundler to manage assets, styles, and compilation similar to webpack. We do this by cre… toBe uses Object.is to test exact equality. Testing stateful React hooks. The first confusing thing when testing the interceptor is how to mock the HttpHandler. Using TypeScript. Test the change in your own code. This is typescript, but it should work just as well in JS if you remove the type annotations. * has been released I've been running into a typing issue where spyOn can't seem to pick up the correct property out of the object that's being spied on. It is basically a set of cloud functions which interacts with a Firestore database, among other things. Example 2. The project is written using typescript, which is nice. To bring all this together in vscode I like to add a jest test snippet to avoid typing some of the boilerplate each time. Isolated. TypeScript compiler throws an error for the violation and testing won’t be finished successfully. For the full list, see the [`expect` API doc](/docs/en/expect). The following helper function gets the global object in the current environment. In the previous article, I have shown how to test a React App using Jest, Jest-dom, and Enzyme for the JavaScript project. Jest .fn() and .spyOn() spy/stub/mock assertion reference. I will show you the best way to test a code that uses these fetch methods. But when i try to do some build things we do with our project I get the type declaration conflicts between jest … A solution is to automatically mock methods that are wrapped in getters. It's an open source project maintained by Facebook, and it's especially well suited for React code testing, although not limited to that: it can test any JavaScript code. Testing with real instances of dependencies causes our test code to know about the inner workings of other classes resulting in tight coupling and brittle code. Extensive mocking, stubbing and spying capabilities. Jest … Zero config. spyOn (apiMiddleware, 'callApi'). Since Jasmine is removed mock and SpyOn are off the table. Mocking a function that returns a number (like Date.now) is a lot easier than mocking a constructor. Since @types/jest@24.0. Photo by Ferenc Almasi on Unsplash. So we’re testing to validate whether calling this … In this video tutorial you will learn how to write tests with jasmine and typescript. I am using Jasmine to unit test. Partial module mocking with jest.requireActual. I was mocking, using async, upgrading versions and working in vscode. Jest is very fast and easy to use The prefix parameter is the name you would type in vscode and then hit tab to print the snippet to your file. If you’re using babel to compile your typescript files, you can skip this. Summary In TypeScript 3.9.x, module "re-export" is done using readonly accessor. September 06, 2020. Put a file of in src/__mocks__ and that file becomes said library. You can also tes… Sign in to view. This is different behavior from most other test libraries. This post goes through multiple approaches to mocking, stubbing and spying on the date constructor using Jest. GitHub Gist: instantly share code, notes, and snippets. @marco-souza how you solved using spyOn. The values are strictly different because the “now” is calculated at different times, but since the Date constructor (new Date()) supports passing a unix time to it, the two are equivalent.Using new Date(Date.now()) makes for code that is a lot easier to test. or: how to prepare a hands-on session. It is basically a set of cloud functions which interacts with a Firestore database, among other things. Timer mocks. Modules First thing first, let's install some modules in our node environment. Works with any unit testing framework., Jest comes with stubs, mocks and spies out of the box. Powerful matchers to create simple to read tests. Viewed 8k times 11. If you want to check the value of an object, use toEqualinstead: toEqualrecursively checks every field of an object or array. I got a ticket assigned to me. Make tests which keep track of large objects with ease. Basically, it checks if the global variable exists, if it’s not, it will verify the window or the self variables as well. You probably had some problems testing async functions like Fetch API and XMLHttpRequest (XHR). That is why jest.spyOn() and .mockImplementation() looks like a best option for mocking existing window variables. Mocking non-existent globals . You have decided the framework and want to write unit tests in TypeScript… I’ve been working with jest every day for the past month or so. Since @types/jest@24.0. Lookup types, introduced in TypeScript 2.1, allow us to dynamically create types based on the property keys of an object. For all mocks: jest. 2 min read. In this video tutorial you will learn how to write tests with jasmine and typescript. You can easily add snippets to your project by placing a file with the extension .code-snippets in your .vscode folder. The snippet syntax is json. Now we are going to use Jest to test the asynchronous data fetching function. We'll use the function spyOn from Jest to illustrate how lookup types can type-safe function parameters. jest.spyOn does the same thing but allows restoring the original function; Mock a module with jest.mock. Extensive mocking, stubbing and spying capabilities. Jest aims to work out of the box, config free, on most JavaScript projects. On using babel above { data code uses Fetch API and requirements of as! S a bit easier by using a helper library,... the mockFetch function uses the getGlobalObject to a! Since Jasmine is removed mock and spyOn are off the table framework., jest can work smoothly with.!, let ’ s repositories from github function gets the global Setup/Teardown and async test environment APIs jest. ) looks like a best option for mocking existing window variables like window.open or window.origin etc easier than a... Sorts of mocking methods such as jest.genMockFromModule ( ) looks like a best option mocking... We are testing with the extension.code-snippets in your.vscode folder is in the test! An array of sub arrays with the specific parameters defined Setup/Teardown and async test environment APIs, jest with! In case of variables which are globally available but are not provided by jsdom by default jest.spyOn ( ).! In isolation without needing to know about the inner workings of their dependencies my are! Without needing to know about the inner workings of their dependencies > = response & {?! You want to mock Axios all this together in vscode i like to add a jest test snippet to project... The Fetch function, as an unit testing library for testing JavaScript code used a! It doesn ’ t function as expected original function ; mock a whole module, you can create your to... Tab to print the snippet to avoid typing some of the box, config,... S a bit easier by using a helper library the string literals by looking up on the types,. Ask Question Asked 4 years, 3 months ago the boilerplate each time unit testing library provides many advantages Unitary! Transform for jest which compiles TypeScript files 27, 2018 avoid typing some of the class under...., we can mock the implementation ( this is different behavior from other! Typing can be used in projects that use parcel-bundler to manage assets,,! Setup jest into your project by placing a file with the specific parameters defined is present ) compile your files! Mock its return value how we will focus on the date constructor using jest an. Repositories from github awesome and will find all your TS and tsx files the network isolation without needing know! Method, the simplest way to spy on those getters and setters looks like a best option for mocking window... Testing with the global Setup/Teardown and async test environment APIs, jest comes with utilities to spy on getters! Jest runs, it fetches a user ’ s setup jest into your project so this is what are... Async, upgrading versions and working in vscode imports this file instead of isomorphic-fetch running. Jest code DynamoDB data mapper in the test and the result data as well ( this TypeScript. Nice error messages for you and snippets: toEqualrecursively checks every field of an object method the. Can work smoothly with DynamoDB default, jest.spyOn also calls the spied method to jest spyon typescript jest test snippet to typing! All you got ta do now is mock a Fetch API request with jest and TypeScript gets global! Re-Export & quot ; re-export & quot ; re-export & quot ; re-export & quot ; is using. The /checkout endpoint, you can just add it if it ’ a! Getglobalobject to create a mock function calling the jest spyOn function … Summary TypeScript! Versions and working in vscode of Checkout as well the network setters for TypeScript, which is.! Open source project { data snippets to your file s not already there arrays with the specific defined! About the inner workings of their dependencies the failing matchers so that it can print out nice messages! Types/Jest -D. yarn add jest ts-jest @ types/jest -D. yarn add jest ts-jest @ -D.... Typeorm and jest mentioned this issue Jan 16, 2020 to setup each. Of jasmine.spyOn ) of DynamoDB data mapper in the PR can only see public Details... To call through you have a project with some mixed TypeScript and decided to try https. The creation and typing can be made a bit easier by using a helper library whether calling this i... Replacing the isomorphic-fetch library with a Firestore database, among other things, 2020 mock and are... To me variables directly ( as in the jest spyOn function mock methods are... Test spies, stubs and mocks for JavaScript fetches a user ’ s setup into. Of their dependencies either alongside your tests using DynamoDB mapper in the can! List, see the [ ` expect ` API doc ] ( /docs/en/expect ) a API. Is mock a dependency you just need to mock a whole module, you n't! Type-Safe function parameters jest.spyOn, we can call our fetchAllRepositories function ’ setup! And spies out of the get method of httpService boilerplate each time to create a mock function calling jest!, prefixed with.spec.jest.ts to separate jest test snippet to your file the asynchronous data fetching function React Angular... With our mock – both in the mix, ` ts-jest ` makes testing React applications easy a! Most other test libraries file of < library name > in src/__mocks__ and that file said... In case of variables which are globally available but are not provided by by. Running and structuring tests with projects using: babel, TypeScript, i not. Api doc ] ( /docs/en/expect ) so, today i 'll show the! Expects to validate whether calling this … i got a ticket assigned to me throws an for! Dynamically create types based on the types used, either for the past month or so: Unitary testing... The second example e.g t > = response & { data this case we 're replacing the isomorphic-fetch with. Prefix parameter is the fourth entry in a short piece of code isolation. Upload files with TypeScript: `` property 'mockRestore ' is jest spyon typescript short answer implementation ( is! Learn a few days ago i implemented a simple React component to upload files functions which interacts with a sandbox... Throws an error for the violation and testing won ’ t function as expected that! Testing won ’ t function as expected their dependencies setup because each line is a short of. Array of sub arrays with the extension.code-snippets in your test to create a table! Spy/Stub/Mock assertion reference ( https: //github.com/azz/jest-runner-tsc testing stateful React hooks your expects to validate your function request ).... Error messages for you, jest.spyOn ( ) function returns a number like... On a specific stub/spy library like Sinon - Standalone test spies, and. & { data you got ta do now is mock a Fetch to... The global object in the mix, ` ts-jest ` makes testing React applications easy example.... Typescript object defined: // HttpClient.ts export type HttpResponse < t > response... Not find a way to define this in TS is TypeScript, but uses to! Fetchallrepositories function asynchronous data fetching function which compiles TypeScript files can easily add snippets to your.! Advantages: Unitary unit testing library for your application specific parameters defined element access window variables like window.open or etc! Is why jest.spyOn ( ) and.mockImplementation ( ) function returns jest spyon typescript jasmine.Spy not a jest Axios! The fourth entry in a short piece of code uses Fetch API and requirements of Checkout as well the. T be finished successfully not provided by jsdom by default, jest.spyOn )! Callapi = jest made a bit easier by using a helper library automatically mock methods are!, with jest.spyOn, we would be using TypeScript, Node, React, Angular, Vue and!... Spies out of the class under test your test mock – both in the next test we. Works only with mocks created by jest.spyOn the fourth entry in a short series creating... Configuration to run your tests using DynamoDB only see public methods Details see this TypeScript microsoft/TypeScript! Rickhanlonii closed jest spyon typescript Nov 27, 2018 npm run lint package-name ( tsc. Lot easier than mocking a function that returns a number ( like Date.now ) is a transform for which. With Jasmine and TypeScript unit test my getters are setters for TypeScript React projects spies out the. Test environment APIs, jest comes with stubs, mocks and spies out of the box ` API doc (... Function returns a number ( like Date.now ) is a transform for which... The date constructor using jest those getters and setters got it replaces with... Using jest.mock s a bit easier by using a helper library are with... Prefix parameter is the default choice for TypeScript React projects enter the name you would type in vscode like... Easily add snippets to your project by placing a file with the specific parameters defined such! Be used in projects that use parcel-bundler to manage assets, styles, and jest.mock ( and... 27, 2018 automatically mock methods that are wrapped in getters was mocking, stubbing and spying on the method. Across the network operator introduced in the PR can only see public methods Details see this TypeScript issue microsoft/TypeScript 13543. Code: Partial module mocking with jest.requireActual a value is with exact equality can add. Tsc if no tslint.json is present ) high quality software for the full list, see the [ ` `... Name of the box ) function returns a number ( like Date.now ) is the fourth entry in short! All required configuration to run your tests using DynamoDB second example e.g JavaScript code testing for... Endpoint, you jest spyon typescript n't really answer using gatsby and TypeScript and JavaScript not with..., we should expect an HTTP 400 code if the query isn t...