// `promassert` is the easiest way to test prometheus metrics in go unit tests.
// It handles the hard parts so you can test metrics using one-line assert statements.
//
// `promassert` works by scraping the prometheus exposition format, in-memory, from promhttp.Handler().
// Each member of the ParsedMetrics slice represents one line in the exposition format.
// Each line itself represents a unique collection label combinations, and their values.
// For example, you might see the following lines for the metric "http_requests_total":
//
//	# HELP http_requests_total The total number of HTTP requests.
//	# TYPE http_requests_total counter
//	http_requests_total{method="post",code="200"} 42
//	http_requests_total{method="post",code="204"} 777
//	http_requests_total{method="get",code="404"} 8
//
// Parsing this metric would return a slice containing 3 members.
//
//	pm := promassert.Counter("http_requests_total") // this scrapes and parses the metric
//
// That slice can be used as-is when testing across all the labels and values:
//
//	pm.Exists(t)                           // true
//	pm.Equals(t, 42.0 + 777.0 + 8.0)       // true
//	pm.LabelKeysExist(t, "method", "code") // true
//
// ParsedMetrics can be filtered based on labels:
//
//	labels := map[string]string{"method":"post"}
//	pm.With(labels).Exists(t)               // true
//	pm.With(labels).Equals(t, 42.0 + 777.0) // true
//	labels["code"] = "204"
//	pm.With(labels).Exists(t)        // true
//	pm.With(labels).Equals(t, 777.0) // true
//
// Sometimes you need to exit immediately when an assertion fails.
// Simply check the returned value and return:
//
//	if !pm.Exists(t) {
//	    return
//	}
//
// For more advanced testing, you can inspect the ParsedMetrics values directly.
// A good strategy when using the `go test --count=N` flag, is to get the value at the beginning of the test.
// Then do whatever increases the metric, and assert based on that value.
//
//	value := pm.TryFold()
//	callSomeHTTPRequests()
//	// you must reparse the metric after it changes.
//	promassert.Counter("http_requests_total").GreaterThan(t, value)
//
// When `promassert.Verbose` is true, the assert library logs assertions.
//
// Every assert statement can take a nil `testing.T` as an argument.
// This feature is used for sad path testing in the `promassert_test` package.
// Providing a nil `testing.T` value turns off logging since logging uses `t.Logf(...)`
//
// For questions or comments, please reach out to Mathew Reny on slack.
package promassert