assertable method
Returns a deterministic, human-readable string representation of this map.
Values for each key are sorted alphabetically before joining, ensuring a consistent output regardless of insertion order. This makes it suitable for comparing expected vs. actual results in tests.
Implementation
String assertable() {
return entries.map((entry) {
var sorted = entry.value;
sorted.sort((a, b) => a.compareTo(b));
return '${entry.key}: ${sorted.join(',')};';
}).join('\n');
}