Add testing guideline

docs/creating-nodes/first-node.md

@@ -230,4 +230,4 @@ These tests check to see that the node is loaded into the runtime correctly, and
 
 Both tests load the node into the runtime using `helper.load` supplying the node under test and a test flow  The first checks that the node in the runtime has the correct name property.  The second test uses a helper node to check that the output from the node is, in fact, lower case.
 
-The helper module contains other examples of tests taken from the Node-RED core nodes.  For more information on the helper module, see the associated README.
+The helper module contains other examples of tests taken from the Node-RED core nodes.  For more information on the helper module, see the [testing guide](testing).

docs/creating-nodes/testing.md

@@ -0,0 +1,271 @@
+---
+layout: docs
+toc: creating-nodes-toc.html
+title: Testing
+---
+
+This guideline explains how to write and execute test code for node.
+
+Because nodes run in Node-RED, you cannot execute the processing of individual units of HTML or JavaScript to test processing.
+In addition, if you use manual testing, you need to stop and restart Node-RED after each test so that cleanup processing takes place.
+This makes testing quite time-consuming.
+Therefore, a tool called [Node Test Helper](https://github.com/node-red/node-red-node-test-helper) (hereafter "helper") has been developed for Node-RED.
+This tool provides a framework for node testing.
+By using this framework, you can easily run nodes at the code level.
+
+Node-RED uses the following libraries for testing, and we recommend their use when using the test code.
+You will need to have an understanding of the specifications of these libraries when creating test code.
+Read the documentation of each library and learn how to use it.
+
+| No. | Library | Purpose | URL |
+| --- | --- | ---| --- |
+| 1 | Mocha | Test framework | [https://mochajs.org](https://mochajs.org/) |
+| 2 | Should.js | Assertion | [https://shouldjs.github.io](https://shouldjs.github.io/) |
+| 3 | Sinon.js | Test double | [http://sinonjs.org](http://sinonjs.org/) |
+| 4 | Nock | Test double | [https://github.com/nock/nock](https://github.com/nock/nock) |
+| 5 | Istanbul | Coverage | [https://github.com/gotwarlost/istanbul](https://github.com/gotwarlost/istanbul) |
+
+### Creating test code
+
+Creating test code consists of the following steps:
+
+1. Preparing the environment
+2. Creating the test code
+3. Running the test code
+
+### 1. Preparing the environment
+
+Use `npm` to install the modules required for testing in the directory in which you are developing your custom node.
+
+```bash
+npm install node-red-node-test-helper should mocha --save-dev
+```
+
+Install modules like `sinon` and `nock` as needed.
+
+### 2. Creating the test code
+
+Create a spec file that contains the test directory and the test code.
+You would typically create a `test` directory in the same directory as package.json, and use the naming rule `file-to-be-tested_spec.js` for the test files themselves.
+[Example]
+
+```text
+.
+├── test-node.js
+├── test-node.html
+├── package.json
+└── test
+    └── test-node_spec.js  // As the spec file for test-node.js, the file name is test-node_spec.js
+```
+
+The processing of test code typically follows this sequence:
+
+1. Load libraries
+2. Initialize helper
+3. Start helper
+4. Load test flow into helper
+5. Run test flow in helper
+6. Evaluate processing results
+7. Exit helper
+
+The following explains how to create test code based on the [example](https://github.com/node-red/node-red-node-test-helper#Example-unit-test) in the helper.
+The test code is written using Mocha.
+Specific details about Mocha are not given here, but you can learn about writing test code in Mocha by visiting the preceding URL and other resources.
+
+```javascript
+// 1. Load libraries
+var should = require("should");
+var helper = require("node-red-node-test-helper");
+var lowerNode = require("../lower-case.js");
+
+// 2. Initialize helper
+helper.init(require.resolve('node-red'));
+
+describe('myNode', function () {
+
+  // 3. Start helper
+  beforeEach(function (done) {
+      helper.startServer(done);
+  });
+
+  // 7. Exit helper
+  afterEach(function (done) {
+      helper.unload();
+      helper.stopServer(done);
+  });
+
+  // Test case
+  it('should make payload lower case', function (done) {
+    // Define test flow
+    var flow = [{ id: "f1", type:"tab"},
+                { id: "n1", z:"f1", type: "lower-case", wires:[["n2"]] },
+                { id: "n2", z:"f1", type: "helper" }];
+    // 4. Load test flow into helper
+    helper.load(lowerNode, flow, function () {
+      var lowerCase = helper.getNode("n1");
+      var helperNode = helper.getNode("n2");
+      // 6. Evaluate processing results
+      helperNode.on("input", function (msg) {
+        msg.should.have.property('payload', 'uppercase');
+        done();
+      });
+      // 5. Run test flow in helper
+      lowerCase.receive({ payload: "UpperCase" });
+    });
+  });
+
+  it('should do something', function (done) {
+    // Write test codes here ...
+  });
+});
+```
+
+#### 1. Load libraries
+
+As a minimum, you will need to load the following libraries:
+
+1. should.js
+2. node test helper
+3. The node to be tested (lower-case.js in the example)
+
+Add libraries like sinon.js as needed.
+
+#### 2. Initialize helper
+
+The helper does not in itself have the ability to run nodes and does so by referencing code in the Node-RED platform.
+Give helper access to the code of the Node-RED platform by passing the Node-RED path to `helper.init()`.
+
+#### 3. Start helper and 7. Exit helper
+
+If you start helper and then run multiple test cases, the results of a test case might remain in helper and contaminate the results of other test cases.
+For this reason, you must exit and restart helper after each test case.
+You can make sure this takes place by calling the startup and shutdown of helper in `beforeEach` and `afterEach` functions.
+
+#### 4. Load test flow into helper
+
+Define the test flow to run as the test case, and load it into the helper.
+If your custom node has an output terminal and you want to evaluate its output results, we recommend that you create a flow using a __helper node__.
+A helper node is a mock node provided by the helper.
+You can check the output of a node you are testing by creating a flow in which a helper node is the succeeding node.
+
+We recommend that you define a tab as part of a test flow (this corresponds to `{ id: "f1", type:"tab"},` in the example).
+Although the code will run without a tab definition, if you do not specify one, the code is deployed internally to a tab named `global`.
+This means processing such as catch nodes and flow contexts that apply within a flow will not work correctly.
+We recommend that you include a tab definition to better simulate a real-world environment.
+
+Nodes that use credentials can be accommodated by passing arguments as shown in the following API request:
+
+Load API request of Node Test Helper in Version 0.1.7
+
+```javascript
+load(testNode, testFlows, testCredentials, cb)
+```
+
+| No. | Argument | Required | Description |
+| --- | --- | ---| --- |
+| 1 | `testNode` | Yes | Node to be tested |
+| 2 | `testFlows` | Yes | Flow definition to be run by helper |
+| 3 | `testCredentials` | No | Credentials to pass to helper |
+| 4 | `cb` | Yes | Callback function executed after loading the flow |
+
+#### 5. Run test flow in helper
+
+Note: As in the preceding example, write the test code so that this step is executed after "6. Evaluate processing results".
+
+Most nodes execute processing in response to a certain action, such as receiving a message from the preceding node.
+This means that you need to write processing into the test case that triggers the execution of the node.
+For nodes with input terminals (nodes whose processing is triggered by receiving a message from the preceding node), you can use `receive` to pass a msg object to the node being tested as follows:
+
+``` javascript
+lowerCase.receive({ payload: "UpperCase" });
+```
+
+For nodes without an input terminal, you need to write the processing that the node expects.
+Because each node is executed in a different way, we have provided samples of core nodes for reference:
+
+* [tail node](https://github.com/node-red/node-red/blob/master/test/nodes/core/storage/28-tail_spec.js#L69-L70)  
+  A tail node monitors a specific file, and when information is added to the file, sends the additions as a message to the succeeding node.
+  Node execution is triggered by using an `fs` module to add a character string to the file.
+
+* [websocket node](https://github.com/node-red/node-red/blob/master/test/nodes/core/io/22-websocket_spec.js)  
+  A websocket node can add a WebSocket server and send data received from a client to the succeeding node (or send data to the client).
+  The node is executed by using a `ws` module to create a WebSocket client and sending data to it.
+
+#### 6. Evaluate processing results
+
+Use `should.js` to write an expression that evaluates the processing results of the node.
+If you want to evaluate the messages output by the node being tested, you can do so in an `input` listener in the helper node, as shown in the example.
+An `input` listener is an event that is called when there is output from the preceding node.
+It is passed as an argument of the message output of the preceding node.
+
+#### Sample test code
+
+For reference, sample code for node testing is provided at the following locations:
+
+* [core node test case](https://github.com/node-red/node-red/tree/master/test/nodes/core)
+* [node-red-nodes test case](https://github.com/node-red/node-red-nodes/tree/master/test)
+* [node-red-web-nodes test case](https://github.com/node-red/node-red-web-nodes/tree/master/test)
+
+### 3. Running the test code
+
+After creating the test code, you can run the test by executing the following command:
+
+```bash
+mocha \"test/**/*_spec.js\"
+```
+
+### Testing a node that calls a custom system (external service)
+
+When testing a node that calls a custom system or other external service in the __local environment__, the processing of the node cannot be executed if the external service cannot be accessed from the local environment.
+You can test this kind of node in a way that does not depend on the environment by creating test code that uses a stub.
+Particularly in the case of unit testing, there is a good chance that the test code will be executed in different environments, such as that of another developer or a CI/CD environment.
+For this reason, we recommend that you create test code that does not depend on the environment.
+When the time comes to conduct integration testing or system testing, use the actual external system in the test instead of the stub.
+
+#### Creating a stub
+
+By way of example, this section explains how to create a stub for a custom system (external service) that has an HTTP API.
+
+* Using [nock](https://github.com/nock/nock) to create a stub (recommended)  
+
+  `nock` is a module created to test HTTP requests.
+  It implements a request stub by partially overriding the standard `http` module.
+  `nock` allows you to create stubs with relatively simple coding and is easier to learn than `express`.
+
+  * Examples of test code creation
+    * [node-red-web-nodes test code](https://github.com/node-red/node-red-web-nodes/tree/master/test)
+      The test code for most nodes is created by using `nock`.
+
+* Using [express](https://github.com/expressjs/express) to create a stub
+
+  `express` is a framework for web application development.
+  You can use `express` to create a web server deployed locally, and send requests to that web server during testing.
+  The web server works as a stub web server, which makes the test non-dependent on external factors.
+  Consider creating a stub web server in `express` when testing processing that includes special requests beyond the capabilities of `nock`.
+
+  * Example of test code creation
+    * [httprequest node](https://github.com/node-red/node-red/blob/master/test/nodes/core/io/21-httprequest_spec.js)
+      By creating a `testServer` in the test code that returns a specific response and issuing any requests to `testServer`, you can perform testing without connecting to a web server outside the local environment.
+
+### Notes on automatic testing by using test code
+
+* Using a test double  
+  The use of a test double offers many advantages, including freedom from dependencies and the ease with which behavior can be verified.
+  Make sure that you have a thorough understanding of `nock` or `sinon` and are able to use it as the situation requires.
+
+* Using settings.js during testing
+  As of Version 0.1.7, Node Test Helper loads a substantially empty settings.js file that it creates internally.
+  You cannot use a customized settings.js file during testing.
+  If the node you are testing contains code that references settings in settings.js, you might be unable to test it using test code.
+
+* OS dependence  
+  Node-RED runs on the node.js platform and is generally OS-independent provided that node.js is available.
+  However, when executing functions that use OS resources such as file access or command execution, the behavior might differ depending on the operating system.
+  Testing should ideally be conducted in the most commonly used OS environments, namely Linux, Windows, and macOS.
+
+## Test items specific to node development
+
+* Testing package.json  
+  When Node-RED loads a custom node, it references the package.json file associated with the node.
+  If the code in package.json contains an error, Node-RED will be unable to load the node correctly.
+  We recommend that you conduct a test in which you use the `npm` command to create an npm package for the custom node and load it in Node-RED.