anchor.diff:  
   test_format() ->
     prometheus_gauge:new([{name, pool_size}, {help, "MongoDB Connections pool size"}]),
  -  prometheus_counter:new([{name, http_requests_total}, {help, "Http request count"}]),  
  +  prometheus_counter:new([{name, http_requests_total}, {help, "Http request count"}]),
     prometheus_counter:new([{name, dtest}, {help, "qwe"}]),
     prometheus_summary:new([{name, orders_summary}, {help, "Track orders count/total sum"}]),
  +  prometheus_summary:new([{name, dsummary}, {help, "qwe"}]),
     prometheus_histogram:new([{name, http_request_duration_milliseconds},
                               {labels, [method]},
                               {bounds, [100, 300, 500, 750, 1000]},
  
positive.code:   prometheus_counter:inc(http_requests_total),
    prometheus_summary:observe(orders_summary,  10),
    prometheus_summary:observe(orders_summary,  15),
    prometheus_histogram:observe(http_request_duration_milliseconds, [get], 95),
    prometheus_histogram:observe(http_request_duration_milliseconds, [get], 100),
    prometheus_histogram:observe(http_request_duration_milliseconds, [get], 102),
  
negative.code:   ?_assertEqual("# TYPE pool_size gauge
  # HELP pool_size MongoDB Connections pool size
  pool_size 365
  # TYPE dtest counter
  # HELP dtest qwe
  dtest 6.5
  # TYPE http_requests_total counter
  # HELP http_requests_total Http request count
  http_requests_total 1
  # TYPE orders_summary summary
  # HELP orders_summary Track orders count/total sum
  orders_summary_count 2
  orders_summary_sum 25
  # TYPE dsummary summary
  # HELP dsummary qwe
  dsummary_count 2
  dsummary_sum 4.2
  # TYPE http_request_duration_milliseconds histogram
  # HELP http_request_duration_milliseconds Http Request execution time
  http_request_duration_milliseconds_bucket{method=\"post\",le=\"100\"} 0
  http_request_duration_milliseconds_bucket{method=\"post\",le=\"300\"} 1
  http_request_duration_milliseconds_bucket{method=\"post\",le=\"500\"} 3
  http_request_duration_milliseconds_bucket{method=\"post\",le=\"750\"} 4
  http_request_duration_milliseconds_bucket{method=\"post\",le=\"1000\"} 5
  http_request_duration_milliseconds_bucket{method=\"post\",le=\"+Inf\"} 6
  http_request_duration_milliseconds_count{method=\"post\"} 6
  http_request_duration_milliseconds_sum{method=\"post\"} 4350
  http_request_duration_milliseconds_bucket{method=\"get\",le=\"100\"} 3
  http_request_duration_milliseconds_bucket{method=\"get\",le=\"300\"} 6
  http_request_duration_milliseconds_bucket{method=\"get\",le=\"500\"} 7
  