Generate assert function for each metric in mdatagen (#12179)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Completion of #12167 , cc @bogdandrutu 

Updated one test to verify the change, will update the rest ones after
this PR merges.
<!-- Issue number if applicable -->
#### Link to tracking issue
n/a

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Added

<!--Describe the documentation added.-->
#### Documentation
Added
<!--Please delete paragraphs that you did not use before submitting.-->

Author: sincejune

.chloggen/generate-metric-assert-funcs.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: mdatagen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Generate assert function for each metric in mdatagen
+
+# One or more tracking issues or pull requests related to the change
+issues: [12179]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

cmd/mdatagen/internal/samplereceiver/internal/metadatatest/generated_telemetrytest.go

@@ -28,7 +28,7 @@ func SetupTelemetry(opts ...componenttest.TelemetryOption) Telemetry {
 	return Telemetry{ Telemetry: componenttest.NewTelemetry(opts...) }
 }
 
-{{- if or isConnector isExporter isExtension isProcessor isReceiver isScraper }}
+{{ if or isConnector isExporter isExtension isProcessor isReceiver isScraper }}
 func (tt *Telemetry) NewSettings() {{ .Status.Class }}.Settings {
 	set := {{ .Status.Class }}test.NewNopSettings()
 	set.ID = component.NewID(component.MustNewType("{{ .Type }}"))
@@ -42,15 +42,45 @@ func (tt *Telemetry) AssertMetrics(t *testing.T, expected []metricdata.Metrics,
 	require.NoError(t, tt.Reader.Collect(context.Background(), &md))
 	// ensure all required metrics are present
 	for _, want := range expected {
-		got := getMetric(want.Name, md)
+		got := getMetricFromResource(want.Name, md)
 		metricdatatest.AssertEqual(t, want, got, opts...)
 	}
 
 	// ensure no additional metrics are emitted
 	require.Equal(t, len(expected), lenMetrics(md))
 }
 
-func getMetric(name string, got metricdata.ResourceMetrics) metricdata.Metrics {
+{{ range $name, $metric := .Telemetry.Metrics }}
+{{ if not $metric.Optional }}
+func AssertEqual{{ $name.Render }}(t *testing.T, tt componenttest.Telemetry, dps []metricdata.{{- if eq $metric.Data.Type "Histogram" }} {{$metric.Data.Type}} {{- end }}DataPoint[{{ $metric.Data.BasicType }}], opts ...metricdatatest.Option) {
+	want := metricdata.Metrics{
+		Name:        "otelcol_{{ $name }}",
+		Description: "{{ $metric.Description }}{{ $metric.Stability }}",
+		Unit:        "{{ $metric.Unit }}",
+		Data:        metricdata.{{ $metric.Data.Type }}[{{ $metric.Data.BasicType }}]{
+			{{- if $metric.Data.HasAggregated }}
+			Temporality: metricdata.CumulativeTemporality,
+			{{- end }}
+			{{- if $metric.Data.HasMonotonic }}
+			IsMonotonic: {{ $metric.Data.Monotonic }},
+			{{- end }}
+			DataPoints: dps,
+		},
+	}
+	got := getMetric(t, tt, "otelcol_{{ $name }}")
+	metricdatatest.AssertEqual(t, want, got, opts...)
+}
+
+{{- end }}
+{{- end }}
+
+func getMetric(t *testing.T, tt componenttest.Telemetry, name string) metricdata.Metrics {
+	var md metricdata.ResourceMetrics
+	require.NoError(t, tt.Reader.Collect(context.Background(), &md))
+	return getMetricFromResource(name, md)
+}
+
+func getMetricFromResource(name string, got metricdata.ResourceMetrics) metricdata.Metrics {
 	for _, sm := range got.ScopeMetrics {
 		for _, m := range sm.Metrics {
 			if m.Name == name {
@@ -70,4 +100,3 @@ func lenMetrics(got metricdata.ResourceMetrics) int {
 
 	return metricsCount
 }
-

cmd/mdatagen/internal/samplereceiver/internal/metadatatest/generated_telemetrytest_test.go

@@ -67,6 +67,20 @@ func TestSetupTelemetry(t *testing.T) {
         {{- end }}
     {{- end }}
     }, metricdatatest.IgnoreTimestamp(), metricdatatest.IgnoreValue())
+
+    {{- range $name, $metric := .Telemetry.Metrics }}
+    {{ if not $metric.Optional }}
+    AssertEqual{{ $name.Render }}(t, testTel.Telemetry,
+        {{ if eq $metric.Data.Type "Gauge" -}}
+        []metricdata.DataPoint[{{ $metric.Gauge.MetricValueType.BasicType }}]{{"{{}}"}},
+        {{- else if eq $metric.Data.Type "Sum" -}}
+        []metricdata.DataPoint[{{ $metric.Sum.MetricValueType.BasicType }}]{{"{{}}"}},
+        {{- else if eq $metric.Data.Type "Histogram" -}}
+        []metricdata.HistogramDataPoint[{{ $metric.Histogram.MetricValueType.BasicType }}]{{"{{}}"}},
+        {{- end }}
+        metricdatatest.IgnoreTimestamp(), metricdatatest.IgnoreValue())
+    {{- end }}
+    {{- end }}
+
 	require.NoError(t, testTel.Shutdown(context.Background()))
 }
-