circleci (v2.0) using npm when yarn is the run command - reactjs

Question

There's documentation on setting up yarn for circleci v1 but not v2 because it appears as though they've got yarn baked into the v2 api, however, in my config.yml i explicitly run yarn to install my deps yet, when i review the build logs it shows that npm is used for all my yarn commands... I obviously need to override this / install yarn? Unfortunately it appears that the v2 docs don't touch on this and my google-foo isn't being fruitful...
what's more interesting is that another one of my projects IS using yarn with almost the exact same config... what gives?
heres my current config.yml
# Javascript Node CircleCI 2.0 configuration file
#
# Check https://circleci.com/docs/2.0/language-javascript/ for more details
#
version: 2
jobs:
build:
docker:
# specify the version you desire here
- image: circleci/node:7.10
# Specify service dependencies here if necessary
# CircleCI maintains a library of pre-built images
# documented at https://circleci.com/docs/2.0/circleci-images/
# - image: circleci/mongo:3.4.4
working_directory: ~/repo
steps:
- checkout
# Download and cache dependencies
- restore_cache:
keys:
- v1-dependencies-{{ checksum "package.json" }}
# fallback to using the latest cache if no exact match is found
- v1-dependencies-
- run: yarn
- save_cache:
paths:
- node_modules
key: v1-dependencies-{{ checksum "package.json" }}
# run tests!
- run: yarn test
- run: echo "ALL GOOD IN THE HOOD"
- deploy:
name: Deploy on deploy branch
command: |
if [ "${CIRCLE_BRANCH}" == "deploy" ]; then
./node_modules/.bin/firebase ...
fi

Answer 1

I figured out the problem. My circleci folder was misspelled. I omitted the . and it was using a default config... sigh...