How do I mock out executing a child process in Jest
const execSync = require('child_process').execSync;
//...
expect(execSync)
.toHaveBeenCalledWith('npm install');
But not actually have it run the npm install during the test.
Can just do something like the following:
jest.mock("child_process", () => {
return {
execSync: () => "This is a test message"
};
});
Where the return value can be a number, string, object or whatever. It just allows you to override the actual implementation of execsync.
You can use lib mock with __mocks__ folder that will hold child_process folder which will be loaded by jest automatically.
Just create a file
// __mocks__/child_process/index.js
module.exports = {
execSync: jest.fn()
};
that will export a mock implementation of child_process.
I'm writing some test scripts and noticed that when I import a specific module and execute a specific function within that module, Mocha runs the entire module plus the one I have specified.
In test.js
const myModule = require('../someModule');
describe('Test',function(){
it('Should run a function in mu module',funciton(){
myModule.someFunction(test);
};
}
In myModule.js
module.exports = { someFunction };
function someFunction(someInput){
return true;
}
Now say I include a console log within my module as shown below:
module.exports = { someFunction };
console.log('Loging inside the module');
function someFunction(someInput){
return true;
}
When I run my Mocha test it will run my funciton but will also run my console.log
Can someone please explain this?
I'm trying to run a simple test with mochajs:
var assert = require('assert'),
ActionCreators = require('../src/components/Dashboard/ActionCreators.js');
describe('', function () {
it('', function () {
assert.equal(1, 1);
});
});
But it throws errors that the ActionCreators file contain import keywords. It does, becuase I run my code with webpack, and it goes through babel.
I've been trying to run this test with mocha-webpack, but it's the same. How should I do this?
Use mocha command line option --compilers js:babel-core/register. Of course you have to have babel-core npm package installed.
I'm writing a web app in Node. If I've got some JS file db.js with a function init in it how could I call that function from the command line?
No comment on why you want to do this, or what might be a more standard practice: here is a solution to your question.... Keep in mind that the type of quotes required by your command line may vary.
In your db.js, export the init function. There are many ways, but for example:
module.exports.init = function () {
console.log('hi');
};
Then call it like this, assuming your db.js is in the same directory as your command prompt:
node -e 'require("./db").init()'
If your db.js were a module db.mjs, use a dynamic import to load the module:
node -e 'import("./db.mjs").then( loadedModule => loadedModule.init() )'
To other readers, the OP's init function could have been called anything, it is not important, it is just the specific name used in the question.
Update 2020 - CLI
As #mix3d pointed out you can just run a command where file.js is your file and someFunction is your function optionally followed by parameters separated with spaces
npx run-func file.js someFunction "just some parameter"
That's it.
file.js called in the example above
const someFunction = (param) => console.log('Welcome, your param is', param)
// exporting is crucial
module.exports = { someFunction }
More detailed description
Run directly from CLI (global)
Install
npm i -g run-func
Usage i.e. run function "init", it must be exported, see the bottom
run-func db.js init
or
Run from package.json script (local)
Install
npm i -S run-func
Setup
"scripts": {
"init": "run-func db.js init"
}
Usage
npm run init
Params
Any following arguments will be passed as function parameters init(param1, param2)
run-func db.js init param1 param2
Important
the function (in this example init) must be exported in the file containing it
module.exports = { init };
or ES6 export
export { init };
As per the other answers, add the following to someFile.js
module.exports.someFunction = function () {
console.log('hi');
};
You can then add the following to package.json
"scripts": {
"myScript": "node -e 'require(\"./someFile\").someFunction()'"
}
From the terminal, you can then call
npm run myScript
I find this a much easier way to remember the commands and use them
Try make-runnable.
In db.js, add require('make-runnable'); to the end.
Now you can do:
node db.js init
Any further args would get passed to the init method, in the form of a list or key-value pairs.
Sometimes you want to run a function via CLI, sometimes you want to require it from another module. Here's how to do both.
// file to run
const runMe = () => {}
if (require.main === module) {
runMe()
}
module.exports = runMe
This one is dirty but works :)
I will be calling main() function from my script. Previously I just put calls to main at the end of script. However I did add some other functions and exported them from script (to use functions in some other parts of code) - but I dont want to execute main() function every time I import other functions in other scripts.
So I did this,
in my script i removed call to main(), and instead at the end of script I put this check:
if (process.argv.includes('main')) {
main();
}
So when I want to call that function in CLI: node src/myScript.js main
simple way:
let's say you have db.js file in a helpers directory in project structure.
now go inside helpers directory and go to node console
helpers $ node
2) require db.js file
> var db = require("./db")
3) call your function (in your case its init())
> db.init()
hope this helps
Updated for 2022 - If you've switched to ES Modules, you can't use the require tricks, you'd need to use dynamic imports:
node -e 'import("./db.js").then(dbMod => dbMod.init());'
or with the --experimental-specifier-resolution=node flag:
node --experimental-specifier-resolution=node -e 'import("./db").then(dbMod => dbMod.init());'
If you turn db.js into a module you can require it from db_init.js and just: node db_init.js.
db.js:
module.exports = {
method1: function () { ... },
method2: function () { ... }
}
db_init.js:
var db = require('./db');
db.method1();
db.method2();
I do a IIFE, something like that:
(() => init())();
this code will be executed immediately and invoke the init function.
You can also run TypeScript with ts-node similar to #LeeGoddard answer.
In my case, I wanted to use app and init separately for testing purposes.
// app.ts
export const app = express();
export async function init(): Promise<void> {
// app init logic...
}
npx ts-node -e 'require("./src/app").init();'
npx ts-node -e 'import("./src/app").then(a => a.init());' // esmodule
maybe this method is not what you mean, but who knows it can help
index.js
const arg = process.argv.splice(2);
function printToCli(text){
console.log(text)
}
switch(arg[0]){
case "--run":
printToCli("how are you")
break;
default: console.log("use --run flag");
}
and run command node . --run
command line
probuss-MacBook-Air:fb_v8 probus$ node . --run
how are you
probuss-MacBook-Air:fb_v8 probus$
and you can add more arg[0] , arg[1], arg[2] ... and more
for node . --run -myarg1 -myarg2
If you want to include environment variables from your .env files, you can use env-cmd:
npx env-cmd node -e 'require("./db").init()'
If you want run a specific function in the file too, use run-func:
npx env-cmd npx run-func db.js init someArg
Or, to provide an argument for the accepted answer you'd have to do something like:
npx env-cmd node -e 'require("./db").init(someArg)'
Writing/updating an expression here is less explicit (so easier to miss when you're checking back, for example) than providing different arguments to the commands, so I recommend using env-cmd with run-func.
Note: I also usually add --experimental-modules on the end when necessary.
Inspired by https://github.com/DVLP/run-func/blob/master/index.js
I create https://github.com/JiangWeixian/esrua
if file index.ts
export const welcome = (msg: string) => {
console.log(`hello ${msg}`)
}
just run
esrua ./index.ts welcome -p world
will output hello world
If your file just contains your function, for example:
myFile.js:
function myMethod(someVariable) {
console.log(someVariable)
}
Calling it from the command line like this nothing will happen:
node myFile.js
But if you change your file:
myFile.js:
myMethod("Hello World");
function myMethod(someVariable) {
console.log(someVariable)
}
Now this will work from the command line:
node myFile.js
I want to run some Jasmine 2.x tests for node.js modules in a Grunt build. My setup looks like this:
src/foo.js
exports.bar = 23;
spec/foo.spec.js
var foo = require("../src/foo.js");
define("foo", function() {
it("exports bar as 23", function() {
expect(foo.bar).toBe(23);
});
});
With grunt-contrib-jasmine the node module system is not available and I get
>> ReferenceError: Can't find variable: require at
>> spec/foo.spec.js:1
There is grunt-jasmine-node, but it depends on jasmine-node which is unmaintained and includes Jasmine 1.3.1, so this is not an option.
Jasmine supports node.js out of the box, by including a file jasmine.json in the spec directory, I can run the tests with the jasmine cli. Is there any clean way to run the same tests from grunt as well?
You could use grunt-exec, which just executes the value as if typed on the command line:
module.exports = function (grunt) {
grunt.initConfig({
exec: {
jasmine: "jasmine"
},
env: {
test: {
NODE_ENV: "test"
}
}
});
grunt.loadNpmTasks("grunt-exec");
grunt.loadNpmTasks("grunt-env");
grunt.registerTask("test", [
"env:test",
"exec:jasmine"
]);
};
This will allow you to keep jasmine up to date as well as use it with other grunt tasks.