Skip metrics collect on first pass and more unit tests

internal/metrics/exporter_test.go

@@ -17,10 +17,88 @@ package metrics
 
 import (
 	"testing"
+	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
 )
 
+func TestDescribe(t *testing.T) {
+
+	teardownTestCase := setupTestCase()
+	defer teardownTestCase()
+
+	ch := make(chan *prometheus.Desc)
+	go func() {
+		exporter := newExporter("qmName")
+		exporter.Describe(ch)
+	}()
+
+	collect := <-requestChannel
+	if collect {
+		t.Errorf("Received unexpected collect request")
+	}
+
+	metrics := initialiseMetrics()
+	responseChannel <- metrics
+
+	select {
+	case prometheusDesc := <-ch:
+		expected := "Desc{fqName: \"ibmmq_qmgr_Element1Name\", help: \"Element1Description\", constLabels: {}, variableLabels: [qmgr]}"
+		actual := prometheusDesc.String()
+		if actual != expected {
+			t.Errorf("Expected value=%s; actual %s", expected, actual)
+		}
+	case <-time.After(1 * time.Second):
+		t.Error("Did not receive channel response from describe")
+	}
+}
+
+func TestCollect(t *testing.T) {
+
+	teardownTestCase := setupTestCase()
+	defer teardownTestCase()
+
+	exporter := newExporter("qmName")
+	exporter.gaugeMap["ClassName/Type1Name/Element1Name"] = createGaugeVec("Element1Name", "Element1Description", false)
+
+	for i := 1; i <= 3; i++ {
+
+		ch := make(chan prometheus.Metric)
+		go func() {
+			exporter.Collect(ch)
+			close(ch)
+		}()
+
+		collect := <-requestChannel
+		if !collect {
+			t.Errorf("Received unexpected describe request")
+		}
+
+		populateTestMetrics(i)
+		metrics := initialiseMetrics()
+		updateMetrics(metrics)
+		responseChannel <- metrics
+
+		select {
+		case <-ch:
+			prometheusMetric := dto.Metric{}
+			exporter.gaugeMap["ClassName/Type1Name/Element1Name"].WithLabelValues("qmName").Write(&prometheusMetric)
+			actual := prometheusMetric.GetGauge().GetValue()
+
+			if i == 1 {
+				if actual != float64(0) {
+					t.Errorf("Expected values to be zero on first collect; actual %f", actual)
+				}
+			} else if actual != float64(i) {
+				t.Errorf("Expected value=%f; actual %f", float64(i), actual)
+			}
+		case <-time.After(1 * time.Second):
+			t.Error("Did not receive channel response from collect")
+		}
+	}
+}
+
 func TestCreateGaugeVec(t *testing.T) {
 
 	ch := make(chan *prometheus.Desc)