z-score function not supported

[binokaryg]

Describe the bug
CHT XPath function z-score does not seem to be supported by test harness. When I use this function, the form does not get filled.

To Reproduce
Steps to reproduce the behavior:

1. Add a z-score function in a form calculation e.g. z-score('weight-for-age', ../my_sex, ../my_age, ../my_weight)
2. Fill the form using test harness (use {headless: false} for visibility)
3. See the browser session getting stuck on the inputs group

What happened?
The form can't be filled and is stuck until it times out.

What did you expect?
Since z-score has been in CHT for a long time, I hoped it would just work.
Screenshots

Environment:

• Harness "coreVersion": "4.11"

Additional context

The z-score function depends on a CouchDB doc zscore-charts which holds the z-score values. So, adding the support might not be straightforward.

[jkuester]

Bad news and good news here. The bad new is that, yeah, there is no support in the test-harness for the z-score function. 😞 The good news is that it should not be too difficult to add support. As with the extension-libs, the most interesting part might be deciding what level of mocking is appropriate/desired for the functionality.

Current Implementation

In cht-core, the z-score xpath funciton depends on a utility that is initialized by the form service with the value returned from the value returned from the z-score service. The utility returned from the z-score service is configured by the contents of a doc in the DB.

In the cht-form component (the web component generated from the cht-core code that is consumed by the test-harness) the z-score XPath function is inited with an empty util value. This is why the z-score function is non-operable in the test-harness.

Possible updates

Essentially, I think we just need to update the cht-form code to initialize the z-score xpath function with the desired functionality. The key point of interest here is to decide if we want to hard-code some z-score table data for the test-harness to use (since we can't just look up a doc in the DB) or perhaps we let the test authors include a specific desired response value from the z-score xpath function (so it is not dependent on the inputs)....