# `DiffoExample.Util`
[🔗](https://github.com/diffo-dev/diffo_example/blob/v0.4.0/lib/diffo_example/util.ex#L5)

Cross-domain projection helpers for the diffo_example app.

Mirrors `Diffo.Util` in shape: each function is a *projection* — it
collapses values in a JSON payload to a coarser semantic form so
comparisons stay meaningful at the projected level. Apply the same
projection to both sides of a comparison.

# `summarise_characteristics`

Project the `*Characteristic` arrays in a JSON payload to a coarser
form derived from `instance`'s declarations.

General-purpose projection helper for comparing TMF payloads at the
*names-only* level, ignoring the specific values carried by typed
characteristic records and pool records. Reads the declared
characteristic, pool and feature characteristic names from the
instance's module and replaces each named characteristic array with a
sorted list of `%{"name" => name, "value" => "absent_characteristic"}`
entries. Applied to both sides of a comparison, names align and rich
values collapse to the same placeholder.

Useful for demonstrating projections — coarsening test assertions to
the structural shape (which characteristics are declared and surface)
without coupling them to the values those characteristics happen to
carry on a given run.

Modelled after `Diffo.Util.summarise_dates/1`.

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*Consult [api-reference.md](api-reference.md) for complete listing*