feat(mocktail): show argument diffs on verify mismatch failures

[theprantadutta]

Status

READY

Breaking Changes

NO — the richer message is only appended when a call to the same member (with the same shape) mismatches on a long/multiline string or a larger collection. For small values the failure message is byte-for-byte identical to today's, and the existing mockito-compat test suite passes unchanged.

Description

Implements the string diffs discussed in #208, following @renancaraujo's suggestion to reuse package:matcher's describeMismatch (I proposed this plan on the issue on May 22).

When verify finds no matching call, mocktail now looks for the closest unverified call — same member, same positional arity / named keys / type arguments, fewest mismatched arguments — and appends a per-argument mismatch description produced by the same Matcher that failed the comparison (equals(value) for concrete values, the wrapped matcher for any(that: ...)).

For the exact scenario from the issue (a long log message that differs only by trailing whitespace), the failure goes from a wall of text you have to eyeball twice, to:

No matching calls. All calls: MockLogger.info(Your next step is to upload the app bundle to the Play Store: build/app/outputs/bundle/release/app-release.aab )
Closest matching call: info
  positional argument #0: is different. Both strings start the same, but the actual value also has the following trailing characters:
(If you called `verify(...).called(0);`, please instead use `verifyNever(...);`.)

Mid-string differences get package:matcher's windowed diff with the ^ marker and Differ at offset N; collections get the mismatched index/key (was <9> instead of <4> at location [3]).

To keep noise down (and existing messages stable), the diff section only triggers when a mismatched value is "large": a string that is multiline or longer than 40 chars, or a collection with more than 5 elements. Small values keep the current short form, since the plain call listing already makes those differences obvious. Both thresholds are constants — happy to tune them or always show the diff if you'd prefer.

Fixes #208

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[theprantadutta]

Gentle bump @felangel — this is ready for review whenever you have a moment. It adds argument diffs to verify failures via package:matcher's describeMismatch (following @renancaraujo's suggestion on #208), with the short form preserved for small values so existing failure output is unchanged. 232/232 tests pass and the analyzer is clean. Happy to rebase if it's drifted.