Camp2 Helpers

Installation

To install it, add this in your package.json file:

"dependencies": {
  "camp2-helpers": "fewlines-education/camp2-helpers#main"
}

Utility functions

expectMessage

import { expectMessage } from "camp2-helpers";

This function modifies the jest expect function and wrap it in a custom package in order to give an extra option to add a message when jest tests fails in TypeScript. It is based the package jest-expect-message for custom use.

You need to install jest for expect to be a global variable.

Reference

The function expectMessage(value, message, style) takes three arguments:

• value, the value tested against a matcher. It is the same argument referenced in the Jest documentation.
• message, a string that is printed only if the expect fails.
• style, either:
  • a string either being "log", "warning", or "error". They represent default styles given to the messages.
    • 
    • 
    • 
  • an object composed of three strings changing respectively the foreground color, background color and effect of the message printed.

  {
    fg?: string;
    bg?: string;
    effects?: string;
  }

Example

With pre-defined style:

test("simple test", () => {
  expectMessage(1 + 1, "This is an error message", "error").toBe(11);
});

// This test will fail and print "This is an error message" in yellow with a red background.

With your own style:

test("simple test", () => {
  expectMessage(1 + 1, "This is my own error message", {fg: "magenta", bg: "cyan", effects: "reverse"}).toBe(11);
});

// This test will fail and print "This my error message" in magenta with a cyan background and reverse !.

Documentation

Those are the different values you can use in the style object:

foreground	background	effect
black	black	reset
red	red	bright
green	green	dim
yellow	yellow	underscore
blue	blue	blink
magenta	magenta	reverse
cyan	cyan	hidden
white	white

readCode

import { readCode } from "camp2-helpers";

This function uses fs.readFile to parse JS files and returns the code as a string.

Reference

The function readCode(path) takes a one argument and returns a promise with a string.

• path, a string refering to the absolute path of a file.

E.g.

import { readCode } from "camp2-helpers";

const code = await readCode("path/of/your/file");

It can be used for testing with jest the following way.

// index.js
const hello = "Hello World!";

// index.test.js
const readcode = require("camp2-helpers");

let code;
beforeAll(() => {
  // Loads the student's code
  code = await readcode("./index.js");

  return code;
});

test("variable 'hello' contains 'Hello World!'", () => {
  return code.then((code) => {
    // Run the code then call the 'hello' variable.
    const hello = eval(code + "; hello;");

    expect(hello).toBe("Hello World!");
  });
});

astNodeParser

import { astNodeParser } from "camp2-helpers";

This function is a parser extending the TypeScript parser from recast. It creates a tree of nodes for every section and element of your code. You can read recast documentation for more information about the tree parser.

Reference

• Cast file into string:

const code = await readCode("./path/to/file.ts");

• Pass the string to the parser, and get the node:

// Class node example
const classNode = findNode(code, "classNode");

• Search deeper into the node:

const classProperty = findNode(classNode, "classProperty");

You can search by name, class member name (e.g. "constructor").

To prevent breaking the tests in case of searching something that is not in the ast, the function returns "undefined".

⚠️ This is a WIP, if you probably should investigate the ast if you can't find what you are looking for.