# Testing Handler

### How to include

> Uses [Custom Middleware Chain](https://github.com/microsoftgraph/msgraph-sdk-javascript/blob/dev/docs/CustomMiddlewareChain.md), it's not included in default middleware chain

### Modes in Chaos Handler

-   Manual mode - Setting the Response code manually. - Global/Client Level - Provide a map declared manually containing response code for the requests. - Request Level - Providing response code per request. This would be overriding the Global level response code (if any).
-   Random mode - We get a random Response code from a set of response code defined for each method.

**A request Passes through to the Graph, if there is no entry for the request**

**Note - Always add ChaosHandler before HttpMessageHandler in the midllewareChain**

### Samples

```js
require("isomorphic-fetch");
const MicrosoftGraph = require("../../lib/src/index.js");
const secrets = require("./secrets");
const fs = require("fs");
// Initialising the client
const client = MicrosoftGraph.Client.init({
	defaultVersion: "v1.0",
	debugLogging: true,
	authProvider: (done) => {
		done(null, secrets.accessToken);
	},
});

/*
Create a custom MiddlewareChain passing information in this way

const manualMap = new Map([["/me/messages/.*", new Map([["GET", 429], ["PATCH", 429]])], ["/me", new Map([["POST", 502]])]]);
const chaosHandler = new MicrosoftGraph.ChaosHandler(new MicrosoftGraph.ChaosHandlerOptions(MicrosoftGraph.ChaosStrategy.MANUAL), manualMap);
*/

// This request would use the Map (Manual mode)
const mail = {
	subject: "Chaos Handler Samples",
	toRecipients: [
		{
			emailAddress: {
				address: "admin@M365x003297.OnMicrosoft.com",
			},
		},
	],
	body: {
		content: "<h1>Testing Handler Samples Sample</h1><br>https://github.com/microsoftgraph/msgraph-sdk-javascript",
		contentType: "html",
	},
};
client
	.api("/users/me/sendMail")
	.post({
		message: mail,
	})
	.then((res) => {
		console.log(res, "This is for sendMail");
	})
	.catch((err) => {
		console.log(err, "This is for sendMail in error case");
	});

// OverRiding to Random mode, providing the chaos percentage as 60(percentage times the error would be generated from handler)
client
	.api("/me")
	.middlewareOptions([new MicrosoftGraph.ChaosHandlerOptions(MicrosoftGraph.ChaosStrategy.RANDOM, "I generated the error", undefined, 60)])
	.get()
	.then((res) => {
		console.log(res);
	})
	.catch((err) => {
		console.log(err);
	});

// This request is passed to the graph and gets a response from the graph, as no entry for /me GET request in the Map
client
	.api("/me")
	.get()
	.then((res) => {
		console.log("Found", res, "users");
	})
	.catch((err) => {
		console.log(err, "!!!!!!!!!");
	});

// Using Manual Map with regex matching
client
	.api("/me/messages/hjdlfslod-fdssdkjfs-6zdkmghs-sadhsu2")
	.header("content-type", "application/json")
	.update({
		birthday: "1908-12-22T00:00:00Z",
	})
	.then((res) => {
		console.log("This is regex matching... Updated Bday");
	})
	.catch((err) => {
		console.log(err, "matched");
	});
```