anchor.diff:    prometheus_counter:inc(http_requests_total),
     prometheus_summary:observe(orders_summary,  10),
     prometheus_summary:observe(orders_summary,  15),
  +  prometheus_summary:dobserve(dsummary, 1.5),
  +  prometheus_summary:dobserve(dsummary, 2.7),
     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),
  
positive.code:   ?_assertEqual("# TYPE pool_size gauge
  # HELP pool_size MongoDB Connections pool size
  pool_size 365
  # TYPE http_requests_total counter
  # HELP http_requests_total Http request count
  http_requests_total 1
  # TYPE dtest counter
  # HELP dtest qwe
  dtest 6.5
  # TYPE orders_summary summary
  # HELP orders_summary Track orders count/total sum
  orders_summary_count 2
  orders_summary_sum 25
  # TYPE http_request_duration_milliseconds histogram
  # HELP http_request_duration_milliseconds Http Request execution time
  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
  
negative.code: http_request_duration_milliseconds_bucket{method=\"get\",le=\"+Inf\"} 9
  http_request_duration_milliseconds_count{method=\"get\"} 9
  http_request_duration_milliseconds_sum{method=\"get\"} 2622
  
  ",
                  binary_to_list(prometheus_text_format:format())).
  