Hello World Example

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.

hello_world.py

import os.path

import openhtf as htf
from openhtf.output.callbacks import json_factory
from openhtf.plugs import user_input


@htf.measures(htf.Measurement('hello_world_measurement'))
def hello_world(test):
    """A hello world test phase."""
    # test.logger writes to the test record (and to the Operator UI).
    test.logger.info('Hello World!')
    # A measurement declared above must be set exactly once.
    test.measurements.hello_world_measurement = 'Hello Again!'


def create_and_run_test(output_dir: str = '.'):
    test = htf.Test(hello_world)

    # {dut_id} is expanded from the record when the file is written.
    test.add_output_callbacks(
        json_factory.OutputToJSON(
            os.path.join(output_dir, '{dut_id}.hello_world.json'), indent=2
        )
    )

    # Ask the operator for the DUT ID; OpenHTF requires one per run.
    test.execute(test_start=user_input.prompt_for_test_start())


if __name__ == '__main__':
    create_and_run_test()

Terminal

$ python hello_world.py
Enter a DUT ID in order to start the test.
--> SN1234

======================= test: openhtf_test  outcome: PASS ======================

What it shows

@htf.measures(htf.Measurement('...'))

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

test.logger.info(...)

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

json_factory.OutputToJSON(pattern, indent=2)

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

user_input.prompt_for_test_start()

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 →

The output file

SN1234.hello_world.json, trimmed:

SN1234.hello_world.json

{
  "dut_id": "SN1234",
  "station_id": "my-laptop",
  "outcome": "PASS",
  "phases": [
    {
      "name": "hello_world",
      "outcome": "PASS",
      "measurements": {
        "hello_world_measurement": {
          "name": "hello_world_measurement",
          "outcome": "PASS",
          "measured_value": "Hello Again!"
        }
      }
    }
  ],
  "log_records": [
    { "level": 20, "logger_name": "openhtf.test_record.<uid>.phase.hello_world", "message": "Hello World!" }
  ]
}

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.

Variations

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.

Measurements example

Validators, units, dimensions, marginal limits.

First test

The same ideas as a guided walkthrough.