props does not necessarily have a fixed length of 2, your code fails to handle cases like a.b.c

Added JavaScript codeblock

Updated to Node v12

JS: Node v12 should be used enabled along with its appropiate assertion tools (Mocha + Chai).
Refer to this and this

JS: No sample tests

The fixed tests are weak and allow wrong solutions to pass.

Examples in the description use wrong comment syntax.

The kata is working fine.

Not an issue.

No random tests.

suggested test cases:

describe("set value", function(){
  let stuff = {};
  it ("set value", function(){
      namespace(stuff, 'moreStuff.name', 'the stuff');
      Test.assertSimilar(stuff, {moreStuff: {name: 'the stuff'}});
  });
});

describe("get value", function(){
  let stuff = {moreStuff: {name: 'the stuff'}};
  it ("valid path", function(){
      Test.assertEquals(namespace(stuff, 'moreStuff.name'), 'the stuff');
  });
  
  it ("invalid path", function(){
      Test.assertEquals(namespace(stuff, 'otherStuff.id'), undefined);
  });
});

^ That. i actually only saw the get-requirement aufter succesfully submitting my solution...

Test didn't pass: Unknown error
Not at all actionable, and it passes all the test cases I wrote for a whole variety of getting and setting.
Failed tests need to provide some kind of feedback.