test: compare native concurrency and server memory

internal/perfcheck/main_test.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+// A load generator must never report a fast failure page as good throughput.
+func TestExchangeRejectsInvalidResponses(t *testing.T) {
+	for _, tt := range []struct {
+		name      string
+		status    int
+		body      string
+		requestID string
+		truncated bool
+		wantOK    bool
+	}{
+		{"valid", 200, expectedBody, "perfCheck", false, true},
+		{"overload", 503, "server busy", "perfCheck", false, false},
+		{"wrongPayload", 200, `{"data":"wrong"}`, "perfCheck", false, false},
+		{"missingRequestId", 200, expectedBody, "", false, false},
+		{"truncated", 200, expectedBody, "perfCheck", true, false},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if r.Header.Get("X-Request-ID") != "perfCheck" {
+					t.Error("client did not send fixed requestId")
+				}
+				w.Header().Set("X-Request-ID", tt.requestID)
+				if tt.truncated {
+					w.Header().Set("Content-Length", "4096")
+				}
+				w.WriteHeader(tt.status)
+				_, _ = w.Write([]byte(tt.body))
+			}))
+			defer server.Close()
+			err := exchange(server.Client(), strings.TrimPrefix(server.URL, "http://"))
+			if (err == nil) != tt.wantOK {
+				t.Fatalf("valid=%v, error=%v", tt.wantOK, err)
+			}
+		})
+	}
+}
+
+func TestPercentileBounds(t *testing.T) {
+	var h histogram
+	// Known ranks, including a tail much slower than the median.
+	for i := 1; i <= 100; i++ {
+		h.add(time.Duration(i) * time.Millisecond)
+	}
+	for _, p := range []uint64{50, 95, 99} {
+		value := h.percentile(100, p)
+		if value < float64(p) || value > float64(p)*1.0625 {
+			t.Fatalf("p%d=%gms outside advertised bucket rounding", p, value)
+		}
+	}
+	if value := h.percentile(0, 95); value != 0 {
+		t.Fatalf("empty histogram returned %g", value)
+	}
+}