Refactor prometheus exporter tests to match file headers as well (#1470)

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

exporters/metric/prometheus/prometheus_test.go

@@ -15,10 +15,8 @@
 package prometheus_test
 
 import (
-	"bytes"
 	"context"
-	"io/ioutil"
-	"net/http"
+	"fmt"
 	"net/http/httptest"
 	"sort"
 	"strings"
@@ -33,11 +31,54 @@ import (
 	"go.opentelemetry.io/otel/sdk/resource"
 )
 
+type expectedMetric struct {
+	kind   string
+	name   string
+	help   string
+	values []string
+}
+
+func (e *expectedMetric) lines() []string {
+	ret := []string{
+		fmt.Sprintf("# HELP %s %s", e.name, e.help),
+		fmt.Sprintf("# TYPE %s %s", e.name, e.kind),
+	}
+
+	ret = append(ret, e.values...)
+
+	return ret
+}
+
+func expectCounterWithHelp(name, help, value string) expectedMetric {
+	return expectedMetric{
+		kind:   "counter",
+		name:   name,
+		help:   help,
+		values: []string{value},
+	}
+}
+
+func expectCounter(name, value string) expectedMetric {
+	return expectCounterWithHelp(name, "", value)
+}
+
+func expectGauge(name, value string) expectedMetric {
+	return expectedMetric{
+		kind:   "gauge",
+		name:   name,
+		values: []string{value},
+	}
+}
+
+func expectHistogram(name string, values ...string) expectedMetric {
+	return expectedMetric{
+		kind:   "histogram",
+		name:   name,
+		values: values,
+	}
+}
+
 func TestPrometheusExporter(t *testing.T) {
-	// #TODO: This test does not adequately verify the type of
-	// prometheus metric exported for all types - for example,
-	// it does not verify that an UpDown- counter is exported
-	// as a gauge. To be improved.
 	exporter, err := prometheus.NewExportPipeline(
 		prometheus.Config{
 			DefaultHistogramBoundaries: []float64{-0.5, 1},
@@ -58,58 +99,58 @@ func TestPrometheusExporter(t *testing.T) {
 	}
 	ctx := context.Background()
 
-	var expected []string
+	var expected []expectedMetric
 
 	counter.Add(ctx, 10, labels...)
 	counter.Add(ctx, 5.3, labels...)
 
-	expected = append(expected, `counter{A="B",C="D",R="V"} 15.3`)
+	expected = append(expected, expectCounter("counter", `counter{A="B",C="D",R="V"} 15.3`))
 
 	_ = metric.Must(meter).NewInt64ValueObserver("intobserver", func(_ context.Context, result metric.Int64ObserverResult) {
 		result.Observe(1, labels...)
 	})
 
-	expected = append(expected, `intobserver{A="B",C="D",R="V"} 1`)
+	expected = append(expected, expectGauge("intobserver", `intobserver{A="B",C="D",R="V"} 1`))
 
 	valuerecorder.Record(ctx, -0.6, labels...)
 	valuerecorder.Record(ctx, -0.4, labels...)
 	valuerecorder.Record(ctx, 0.6, labels...)
 	valuerecorder.Record(ctx, 20, labels...)
 
-	expected = append(expected, `valuerecorder_bucket{A="B",C="D",R="V",le="+Inf"} 4`)
-	expected = append(expected, `valuerecorder_bucket{A="B",C="D",R="V",le="-0.5"} 1`)
-	expected = append(expected, `valuerecorder_bucket{A="B",C="D",R="V",le="1"} 3`)
-	expected = append(expected, `valuerecorder_count{A="B",C="D",R="V"} 4`)
-	expected = append(expected, `valuerecorder_sum{A="B",C="D",R="V"} 19.6`)
+	expected = append(expected, expectHistogram("valuerecorder",
+		`valuerecorder_bucket{A="B",C="D",R="V",le="-0.5"} 1`,
+		`valuerecorder_bucket{A="B",C="D",R="V",le="1"} 3`,
+		`valuerecorder_bucket{A="B",C="D",R="V",le="+Inf"} 4`,
+		`valuerecorder_sum{A="B",C="D",R="V"} 19.6`,
+		`valuerecorder_count{A="B",C="D",R="V"} 4`,
+	))
 
 	upDownCounter.Add(ctx, 10, labels...)
 	upDownCounter.Add(ctx, -3.2, labels...)
 
-	expected = append(expected, `updowncounter{A="B",C="D",R="V"} 6.8`)
+	expected = append(expected, expectGauge("updowncounter", `updowncounter{A="B",C="D",R="V"} 6.8`))
 
 	compareExport(t, exporter, expected)
 	compareExport(t, exporter, expected)
 }
 
-func compareExport(t *testing.T, exporter *prometheus.Exporter, expected []string) {
+func compareExport(t *testing.T, exporter *prometheus.Exporter, expected []expectedMetric) {
 	rec := httptest.NewRecorder()
 	req := httptest.NewRequest("GET", "/metrics", nil)
 	exporter.ServeHTTP(rec, req)
 
 	output := rec.Body.String()
 	lines := strings.Split(output, "\n")
 
-	var metricsOnly []string
-	for _, line := range lines {
-		if !strings.HasPrefix(line, "#") && line != "" {
-			metricsOnly = append(metricsOnly, line)
-		}
+	expectedLines := []string{""}
+	for _, v := range expected {
+		expectedLines = append(expectedLines, v.lines()...)
 	}
 
-	sort.Strings(metricsOnly)
-	sort.Strings(expected)
+	sort.Strings(lines)
+	sort.Strings(expectedLines)
 
-	require.Equal(t, strings.Join(expected, "\n"), strings.Join(metricsOnly, "\n"))
+	require.Equal(t, expectedLines, lines)
 }
 
 func TestPrometheusStatefulness(t *testing.T) {
@@ -123,20 +164,6 @@ func TestPrometheusStatefulness(t *testing.T) {
 
 	meter := exporter.MeterProvider().Meter("test")
 
-	// GET the HTTP endpoint
-	scrape := func() string {
-		var input bytes.Buffer
-		resp := httptest.NewRecorder()
-		req, err := http.NewRequest("GET", "/", &input)
-		require.NoError(t, err)
-
-		exporter.ServeHTTP(resp, req)
-		data, err := ioutil.ReadAll(resp.Result().Body)
-		require.NoError(t, err)
-
-		return string(data)
-	}
-
 	ctx := context.Background()
 
 	counter := metric.Must(meter).NewInt64Counter(
@@ -146,16 +173,13 @@ func TestPrometheusStatefulness(t *testing.T) {
 
 	counter.Add(ctx, 100, attribute.String("key", "value"))
 
-	require.Equal(t, `# HELP a_counter Counts things
-# TYPE a_counter counter
-a_counter{key="value"} 100
-`, scrape())
+	compareExport(t, exporter, []expectedMetric{
+		expectCounterWithHelp("a_counter", "Counts things", `a_counter{key="value"} 100`),
+	})
 
 	counter.Add(ctx, 100, attribute.String("key", "value"))
 
-	require.Equal(t, `# HELP a_counter Counts things
-# TYPE a_counter counter
-a_counter{key="value"} 200
-`, scrape())
-
+	compareExport(t, exporter, []expectedMetric{
+		expectCounterWithHelp("a_counter", "Counts things", `a_counter{key="value"} 200`),
+	})
 }