Force a specific variation through a URL parameter

[rkz]

Context

Let's say we have two experiments running on a view function:

# app.py
@app.route('/')
def index():
    optimize.run('cta_size')
    optimize.run('navbar_color')
    # ...
    return render_template('index.html')

Normally, every user is assigned to a variation for each of the experiments and can't change them.

Goal

As a developer or tester, I want to control which variation I'm assigned to.

Add support to special URL parameters ex_{EXPERIMENT_KEY}={VARIATION_KEY}, such as:

http://my.app/?ex_cta_size=bigger&ex_navbar_color=dark

This would force the variations for the current pageview only.

As a side effect, Google Optimize won't account sessions where different variations for the same experiment are reported.