Test a Python Function

MediumPython

Problem

Motorola's device telemetry team owns this function, which parses a raw signal report string coming off a handset (device id followed by comma-separated dBm samples, for example "MOTO-42,-80,-95,-70,-120") into a summary the dashboard displays.

def parse_signal_report(raw):
    parts = raw.split(",")
    device_id = parts[0]
    samples = [int(x) for x in parts[1:]]

    average = sum(samples) / len(samples)
    peak = max(samples)
    dropout_ratio = len([s for s in samples if s < -100]) / len(samples)

    return {
        "device_id": device_id,
        "average_dbm": round(average),
        "peak_dbm": peak,
        "dropout_ratio": dropout_ratio,
    }

How would you test this function in Python? Describe the specific test cases you would write, including edge cases, and explain what each one would catch.

Write focused unit tests that verify the complete returned dictionary, including exact dropout thresholds, rounding, device ID preservation, and expected exceptions for invalid reports.

Constraints

The input is a non-null string containing a device ID followed by zero or more comma-separated sample fields.
Valid sample fields are decimal integers representing dBm values.
The function returns a dictionary with device_id, average_dbm, peak_dbm, and dropout_ratio.
For valid reports with no samples, the current implementation raises ZeroDivisionError.
For nonnumeric samples, the current implementation raises ValueError.

Function Signature

def test_signal_report_case(raw, expected):