Test a function against baseline output

Let's say you're writing a function that transforms some text into some other text. This package makes testing such a function easy, by letting you set up source files alongside their corresponding desired baseline output files, and then seeing if your function generates the right results.

Example

Let's say you're writing a Markdown-to-HTML converter, and have set up your project like so:

lib/
  md2html.js
test/
  cases/
    bold.md
    bold.html
    paragraphs.md
    paragraphs.html
    ⋮

Here we assume lib/md2html.js has a default export that is a function converting strings of Markdown to strings of HTML, synchronously.

To run the tests using baseline-tester, you can either use the CLI:

$ baseline-tester lib/md2html.js --cases test/cases --input md --output html

or you can do so programmatically (say, from test/runner.js):

"use strict";
var path = require("path");
var baselineTester = require("baseline-tester");
var md2html = require("../lib/md2html.js");

baselineTester(md2html, {
    casesDirectory: path.resolve(__dirname, "cases"),
    inputExtension: "md",
    outputExtension: "html"
});

Trimming

It's common to want to ignore leading or trailing whitespace when comparing against the baseline files. baseline-tester will do this by default, but you can turn it off by specifying --trim=none on the command line or trim: "none" programmatically.

Testing Exceptions

If you want to test that your function throws certain exceptions, you can use a slightly modified setup. On the command line, pass the additional option --exceptions; when used programmatically, pass the additional option checkExceptions: true.

For example, if you stored your exceptional cases under test/exceptions with the exception messages being given extension .txt, you could do

$ baseline-tester lib/md2html.js --exceptions --cases test/exceptions --input md --output txt

Exception messages are checked against the message: i.e., are the contents of the "output" file equal to the exception's message property (modulo potential trimming).