test: add PostWithRetry coverage in credentials

pkg/credentials/request_test.go

@@ -0,0 +1,112 @@
+package credentials
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strconv"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func portFromURL(t *testing.T, rawURL string) int {
+	t.Helper()
+	u, err := url.Parse(rawURL)
+	require.NoError(t, err)
+	port, err := strconv.Atoi(u.Port())
+	require.NoError(t, err)
+	return port
+}
+
+func TestPostWithRetry_ReturnsBodyOnSuccess(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte("payload"))
+	}))
+	t.Cleanup(server.Close)
+
+	out, err := PostWithRetry(portFromURL(t, server.URL), "endpoint", http.NoBody)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("payload"), out)
+}
+
+func TestPostWithRetry_ReturnsErrorOnNon200(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		http.Error(w, "boom", http.StatusInternalServerError)
+	}))
+	t.Cleanup(server.Close)
+
+	start := time.Now()
+	out, err := PostWithRetry(portFromURL(t, server.URL), "endpoint", http.NoBody)
+	elapsed := time.Since(start)
+
+	require.Error(t, err)
+	assert.Nil(t, out)
+	assert.Contains(t, err.Error(), "500")
+	assert.Contains(t, err.Error(), "endpoint")
+
+	assert.Less(t, elapsed, 500*time.Millisecond, "non-200 response must not trigger retries")
+}
+
+func TestPostWithRetry_RetriesConnectionRefusedThenSucceeds(t *testing.T) {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	port := ln.Addr().(*net.TCPAddr).Port
+	require.NoError(t, ln.Close())
+
+	srvCh := make(chan *http.Server, 1)
+	go func() {
+		time.Sleep(150 * time.Millisecond)
+		srvLn, listenErr := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", port))
+		if listenErr != nil {
+			srvCh <- nil
+			return
+		}
+		srv := &http.Server{
+			ReadHeaderTimeout: 5 * time.Second,
+			Handler: http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+				_, _ = w.Write([]byte("recovered"))
+			}),
+		}
+		srvCh <- srv
+		_ = srv.Serve(srvLn)
+	}()
+	t.Cleanup(func() {
+		if srv := <-srvCh; srv != nil {
+			_ = srv.Close()
+		}
+	})
+
+	out, err := PostWithRetry(port, "endpoint", http.NoBody)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("recovered"), out)
+}
+
+func TestPostWithRetry_ExhaustsRetriesOnConnectionRefused(t *testing.T) {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	require.NoError(t, err)
+	port := ln.Addr().(*net.TCPAddr).Port
+	require.NoError(t, ln.Close())
+
+	start := time.Now()
+	out, err := PostWithRetry(port, "endpoint", http.NoBody)
+	elapsed := time.Since(start)
+
+	require.Error(t, err)
+	assert.Nil(t, out)
+	assert.True(t, errors.Is(err, syscall.ECONNREFUSED),
+		"error must wrap ECONNREFUSED after exhausting retries, got: %v", err)
+
+	assert.Greater(
+		t,
+		elapsed,
+		200*time.Millisecond,
+		"connection-refused must be retried before failing",
+	)
+}