# Hello World Example
URL: /examples/hello-world

The canonical OpenHTF hello_world.py example explained — one phase, one measurement, a JSON output callback and a DUT ID prompt — with its console and JSON output.

The smallest useful OpenHTF test: one phase that logs a line and sets a string measurement, written to a JSON file named after the DUT. Based on `examples/hello_world.py`.

Declares the measurement before the phase runs. With no validator, any value passes; an unset value fails. Measurements →

The right way to log from a phase: the record's `log_records` and the Operator UI both receive it, unlike `print()`. Logger →

Output callback writing one file per run. The pattern accepts any record field. Output Callbacks →

A start-trigger phase that prompts for the DUT ID on the console (and in the Operator UI when one is running). Device Under Test →

`SN1234.hello_world.json`, trimmed:

The start trigger is itself a phase and appears first in `phases[]` as `trigger_phase` (omitted above). Every field is documented in the JSON format reference.

Skip the prompt while developing: `test.execute(test_start=lambda: 'SN1234')`.

Print failures to the console as well: `test.add_output_callbacks(console_summary.ConsoleSummary())`.

Send the record to a database in addition to the file: `test.add_output_callbacks(upload())` from `tofupilot.openhtf` — Manufacturing Test Analytics.

<Card title="Measurements example" href="/examples/measurements" description="Validators, units, dimensions, marginal limits." />

<Card title="First test" href="/first-test" description="The same ideas as a guided walkthrough." />