class SimpleCov::StringFilter

configured string at a path-segment boundary.
Filter that matches when the source file’s project path contains the

def compute_segment_pattern 

def compute_segment_pattern
  normalized = filter_argument.delete_prefix("/")
  escaped    = Regexp.escape(normalized)
  boundary   = '(?:\A|/)'
  if normalized.include?(".")
    # Filename pattern (e.g. "test.rb" matches "faked_test.rb"): allow
    # substring match within the last path segment, anchored to a
    # segment boundary.
    %r{#{boundary}[^/]*#{escaped}}
  elsif normalized.end_with?("/")
    # Trailing slash signals directory-only matching.
    /#{boundary}#{escaped}/
  else
    # Directory or path: require a segment-boundary match so "lib"
    # matches "lib/" but not "library/".
    %r{#{boundary}#{escaped}(?=[/.]|\z)}
  end
end

def matches?(source_file)

"/app/models/library.rb".
and be followed by "/" or end-of-string, so "lib" matches "/lib/foo.rb" but not
Matching is path-segment-aware: the argument must appear immediately after a "/"
string configured when initializing this Filter with StringFilter.new('somestring').
Returns true when the given source file's filename matches the 
def matches?(source_file)
  source_file.project_filename.match?(segment_pattern)
end

def segment_pattern 

def segment_pattern
  @segment_pattern ||= compute_segment_pattern
end