React Jest - import JS module without using require/export

Question

Is it possible to use Jest to test individual JavaScript files without using require/export?

Let's say I want to test abc.js. Here is an example of abc.js:

(function(){
   return {
       foo: function(){}
   }
})();

Now let's say my test file is abc.test.js. I want to test if foo is a function. How would I go on about testing this file without using modules.exports in abc.js and require in abc.test.js?

Thanks in advance

This doesn't look possible without transforming the underlying source file before Jest loads it. Is there a reason why you aren't using exports? — Lewis Chung, Apr 30 '17 at 05:01
I don't want to include test code for my source files. I think I will have to use grunt or something to remove it for production — Leo Teng, May 01 '17 at 06:47

Paul Sweatte · Answer 1 · 2018-09-25T22:18:09.917

Use a named function, a try/catch block, and an inline assertion to test it with plain Node.js:

const assert = require('assert');

(function hi(){
  hi.foo = Function;
  try
    {
    assert.ok(typeof hi.foo === 'function', 'Not a function');
    assert.ok(typeof hi.foo === 'string', 'Not a string');
    }
  catch(e)
    {
    console.log(e.message);
    }
  }
)();

then run it:

node foo.js

Comment out the test-oriented code to avoid including it in the source file:

/*const assert = require('assert');*/

(function hi(){
  hi.foo = Function;
  /*
  try
    {
    assert.ok(typeof hi.foo === 'function', 'Not a function');
    assert.ok(typeof hi.foo === 'string', 'Not a string');
    }
  catch(e)
    {
    console.log(e.message);
    }
  */
  }
)();

Then remove the comments programmatically and pipe the output to node in a *nix shell:

cat foo.js | tr -d '/*' | node

or Powershell:

$string = cat foo.js
$string.Split("/*") | node

And use Grunt or another tool to strip out comment blocks in the build process.

References

React Jest - import JS module without using require/export

1 Answers1