TDD = write tests first, then write code/functionality.
So it isn't a good situation if you submit your code with no tests at all.
Someone reviewing your project code as it currently is will see it as if you were asked "In English, write a 500 word essay about why you like development" and then wrote it in French.
If this was an assignment where they expected a TDD process for development, this is difficult to do in "reverse" and likely moreso if you are unfamiliar with it. It sounds like TDD was an integral part of this coding assignment that you knew about but put off until later (??).
I have now completed it but it is missing one aspect of it because I am not familiar with this layer of technology(TDD).
What you should have done (and still could do) was:
- Identify your lack of understanding (TDD)
- Researched this to better understand it
- Then begun development using a TDD methodology
Should I email them and tell them I have deployed the app with no tests and will attempt to finish that within the next two days(approx.)?
No, this will likely cost you the job. Think of the above English/French example for why.
Should I admit to not knowing testing?
If the job requires knowledge and understanding of testing, you should admit this now rather than later. You don't want to pretend you know something and then find out in the first few weeks of the job that you don't know what you made them think you knew.
Alternatively you could and should research testing and practice this.
Would it help if I sent my deployed app or should I wait to present everything altogether?
You probably should review what was being requested of you. If you have questions, make sure you first research those questions and understand what it is you don't know. Then, if you still have questions, you should ask for clarification or mention "I'm not familiar with this technology/approach but am more than willing to learn and have done X, Y, Z to research it so far."