add additional unit test

Author: Sovietaced

instrumentation/net/http/otelhttp/test/transport_test.go

@@ -17,6 +17,8 @@ package test
 import (
 	"bytes"
 	"context"
+	"go.opentelemetry.io/otel/sdk/metric"
+	semconv "go.opentelemetry.io/otel/semconv/v1.20.0"
 	"io"
 	"net"
 	"net/http"
@@ -27,15 +29,12 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk/instrumentation"
-	"go.opentelemetry.io/otel/sdk/metric"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata"
 	"go.opentelemetry.io/otel/sdk/metric/metricdata/metricdatatest"
-	semconv "go.opentelemetry.io/otel/semconv/v1.20.0"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 	"go.opentelemetry.io/otel/codes"
@@ -250,64 +249,139 @@ func TestWithHTTPTrace(t *testing.T) {
 }
 
 func TestTransportMetrics(t *testing.T) {
-	reader := metric.NewManualReader()
-	meterProvider := metric.NewMeterProvider(metric.WithReader(reader))
 
+	requestBody := []byte("john")
 	responseBody := []byte("Hello, world!")
 
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.WriteHeader(http.StatusOK)
-		if _, err := w.Write(responseBody); err != nil {
+	t.Run("make http request and read entire response at once", func(t *testing.T) {
+		reader := metric.NewManualReader()
+		meterProvider := metric.NewMeterProvider(metric.WithReader(reader))
+
+		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+			if _, err := w.Write(responseBody); err != nil {
+				t.Fatal(err)
+			}
+		}))
+		defer ts.Close()
+
+		r, err := http.NewRequest(http.MethodGet, ts.URL, bytes.NewReader(requestBody))
+		if err != nil {
 			t.Fatal(err)
 		}
-	}))
-	defer ts.Close()
 
-	requestBody := []byte("john")
-	r, err := http.NewRequest(http.MethodGet, ts.URL, bytes.NewReader(requestBody))
-	if err != nil {
-		t.Fatal(err)
-	}
+		tr := otelhttp.NewTransport(
+			http.DefaultTransport,
+			otelhttp.WithMeterProvider(meterProvider),
+		)
 
-	tr := otelhttp.NewTransport(
-		http.DefaultTransport,
-		otelhttp.WithMeterProvider(meterProvider),
-	)
+		c := http.Client{Transport: tr}
+		res, err := c.Do(r)
+		if err != nil {
+			t.Fatal(err)
+		}
 
-	c := http.Client{Transport: tr}
-	res, err := c.Do(r)
-	if err != nil {
-		t.Fatal(err)
-	}
+		// Must read the body or else we won't get response metrics
+		bodyBytes, err := io.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		require.Len(t, bodyBytes, 13)
+		require.NoError(t, res.Body.Close())
 
-	// Must read the body or else we won't get response metrics
-	bodyBytes, err := io.ReadAll(res.Body)
-	if err != nil {
-		t.Fatal(err)
-	}
-	require.Len(t, bodyBytes, 13)
-	require.NoError(t, res.Body.Close())
+		host, portStr, _ := net.SplitHostPort(r.Host)
+		if host == "" {
+			host = "127.0.0.1"
+		}
+		port, err := strconv.Atoi(portStr)
+		if err != nil {
+			port = 0
+		}
 
-	host, portStr, _ := net.SplitHostPort(r.Host)
-	if host == "" {
-		host = "127.0.0.1"
-	}
-	port, err := strconv.Atoi(portStr)
-	if err != nil {
-		port = 0
-	}
+		rm := metricdata.ResourceMetrics{}
+		err = reader.Collect(context.Background(), &rm)
+		require.NoError(t, err)
+		require.Len(t, rm.ScopeMetrics, 1)
+		attrs := attribute.NewSet(
+			semconv.NetPeerName(host),
+			semconv.NetPeerPort(port),
+			semconv.HTTPMethod("GET"),
+			semconv.HTTPStatusCode(200),
+		)
+		assertClientScopeMetrics(t, rm.ScopeMetrics[0], attrs)
+	})
+
+	t.Run("make http request and buffer response", func(t *testing.T) {
+		reader := metric.NewManualReader()
+		meterProvider := metric.NewMeterProvider(metric.WithReader(reader))
+
+		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(http.StatusOK)
+			if _, err := w.Write(responseBody); err != nil {
+				t.Fatal(err)
+			}
+		}))
+		defer ts.Close()
+
+		r, err := http.NewRequest(http.MethodGet, ts.URL, bytes.NewReader(requestBody))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		tr := otelhttp.NewTransport(
+			http.DefaultTransport,
+			otelhttp.WithMeterProvider(meterProvider),
+		)
+
+		c := http.Client{Transport: tr}
+		res, err := c.Do(r)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Must read the body or else we won't get response metrics
+		var buf []byte
+		smallBuf := make([]byte, 10)
+
+		// Read first 10 bytes
+		bc, err := res.Body.Read(smallBuf)
+		if err != nil {
+			t.Fatal(err)
+		}
+		require.Equal(t, 10, bc)
+		buf = append(buf, smallBuf...)
+
+		// reset byte array
+		// Read last 3 bytes
+		bc, err = res.Body.Read(smallBuf)
+		require.Equal(t, io.EOF, err)
+		require.Equal(t, 3, bc)
+		buf = append(buf, smallBuf[:bc]...)
+
+		require.NoError(t, res.Body.Close())
+
+		host, portStr, _ := net.SplitHostPort(r.Host)
+		if host == "" {
+			host = "127.0.0.1"
+		}
+		port, err := strconv.Atoi(portStr)
+		if err != nil {
+			port = 0
+		}
+
+		rm := metricdata.ResourceMetrics{}
+		err = reader.Collect(context.Background(), &rm)
+		require.NoError(t, err)
+		require.Len(t, rm.ScopeMetrics, 1)
+		attrs := attribute.NewSet(
+			semconv.NetPeerName(host),
+			semconv.NetPeerPort(port),
+			semconv.HTTPMethod("GET"),
+			semconv.HTTPStatusCode(200),
+		)
+		assertClientScopeMetrics(t, rm.ScopeMetrics[0], attrs)
+	})
 
-	rm := metricdata.ResourceMetrics{}
-	err = reader.Collect(context.Background(), &rm)
-	require.NoError(t, err)
-	require.Len(t, rm.ScopeMetrics, 1)
-	attrs := attribute.NewSet(
-		semconv.NetPeerName(host),
-		semconv.NetPeerPort(port),
-		semconv.HTTPMethod("GET"),
-		semconv.HTTPStatusCode(200),
-	)
-	assertClientScopeMetrics(t, rm.ScopeMetrics[0], attrs)
 }
 
 func assertClientScopeMetrics(t *testing.T, sm metricdata.ScopeMetrics, attrs attribute.Set) {