Spoken narration (unchanged)

Start with the incoming domain. This fictional configuration field receives exact Python integers, including negatives, zero and values above 65535. Its rule accepts 1 through 65535 inclusive and preserves the supplied integer. Other representations, parsing and network binding are outside the recorded calls.

Write what each class is expected to share. Below the accepted interval, the response must say too_low. Above it, the response must say too_high. Accepted values share an input-preservation rule, so different ports have different payloads. The three initial representatives are minus one, 443 and 65536.

The baseline passes those three representative calls. Add witnesses around the two accepted endpoints: zero, one and two; then 65534, 65535 and 65536. The union contains eight distinct values because 65536 appears in both selections. These witnesses challenge the assumption of shared implementation behavior without establishing behavior for every member.

At 65535, the baseline returns accepted false and reason too_high. The independent literal expectation is accepted true with port 65535. The actual comparison rejects values greater than or equal to the upper endpoint. This witness exposes a violation inside the class sampled successfully by 443.

The corrected upper check rejects only values greater than 65535. Its refined selection passes all eight calls. The accept-all control fails the three selected invalid values, and the reject-all control fails the five selected valid values. The harness compares whole responses, including exact dictionary keys, field types and values.

Keep the conclusion attached to its evidence. Six recorded gates make 41 repeated helper calls, using eight distinct integers on Python 3.14.7. They establish these selected outcomes. Broader class equivalence, parser behavior and production acceptance remain unestablished. Use the worksheet to assign the next evidence needed for your actual interface.

Reader notes for the standalone download (not spoken narration)

Public article: https://reqproof.com/topics/equivalence-partitioning#example

Recorded gate | Passed / helper calls
Baseline, representatives | 3 / 3
Baseline, six endpoint neighbors | 5 / 6
Baseline, refined eight | 7 / 8
Corrected, refined eight | 8 / 8
Accept-all control, refined eight | 5 / 8
Reject-all control, refined eight | 3 / 8

Across the six gates, 3 + 6 + 8 + 8 + 8 + 8 = 41 helper invocations reuse eight distinct integers.