…espace' by java.lang.Character

The Java regex character class \s is not consistent with Character.isWhitespace (presumably to mimic how older, non-unicode aware regular expressons worked?)
This means that testing for blank strings with \s gives inconsistent results with String.isBlank, which delegates to the Character.isWhitespace implementations.
This new test case demonstrates that inconsistency.

The principal of least astonishment suggests that the matcher should be consistent with the similarly named string method.
The isBlank method does a simple O(N) search through the codepoints of the string and bails out at the first non-whitespace character it finds, so I can't think of any negative performance implications here.
The implementation continues to pass for all original test cases.

String#isBlank is a newer convenience method and not supported on all target platforms