diff --git a/main.go b/main.go
index 63cd14d..9958d99 100644
--- a/main.go
+++ b/main.go
@@ -31,6 +31,14 @@ var (
 )
 
 func init() {
+	// Skip flag parsing during tests
+	if len(os.Args) > 0 {
+		for _, arg := range os.Args {
+			if arg == "-test.v" || arg == "-test.run" || strings.HasPrefix(arg, "-test.") {
+				return
+			}
+		}
+	}
 	flag.Parse()
 	slog.SetLogLoggerLevel(getLogLevel())
 }
diff --git a/routes_handler.go b/routes_handler.go
index 50eb637..914766f 100644
--- a/routes_handler.go
+++ b/routes_handler.go
@@ -17,15 +17,35 @@ import (
 	"github.com/go-chi/chi/v5"
 )
 
+// readRound parses and validates the round parameter from the HTTP request.
+func readRound(r *http.Request) (uint64, error) {
+	roundStr := chi.URLParam(r, "round")
+	if roundStr == "" {
+		return 0, fmt.Errorf("round parameter is required")
+	}
+
+	roundN, err := strconv.ParseUint(roundStr, 10, 64)
+	if err != nil {
+		return 0, fmt.Errorf("invalid round number %q: %w", roundStr, err)
+	}
+
+	// Set a reasonable maximum to prevent issues with time calculations
+	const maxReasonableRound = uint64(1 << 60)
+	if roundN > maxReasonableRound {
+		return 0, fmt.Errorf("round number %d exceeds maximum allowed value %d", roundN, maxReasonableRound)
+	}
+
+	return roundN, nil
+}
+
 func GetBeacon(c *grpc.Client, isV2 bool) func(http.ResponseWriter, *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
-		roundStr := chi.URLParam(r, "round")
-		round, err := strconv.ParseUint(roundStr, 10, 64)
+		round, err := readRound(r)
 		if err != nil {
 			w.Header().Set("Cache-Control", "public, max-age=604800, immutable")
 
-			slog.Error("unable to parse round", "error", err)
-			http.Error(w, "Failed to parse round. Err: "+err.Error(), http.StatusBadRequest)
+			slog.Error("unable to parse round", "error", err, "client", r.RemoteAddr, "path", r.URL.Path)
+			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
 
diff --git a/routes_handler_test.go b/routes_handler_test.go
new file mode 100644
index 0000000..76115b0
--- /dev/null
+++ b/routes_handler_test.go
@@ -0,0 +1,159 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/stretchr/testify/require"
+)
+
+func TestReadRound(t *testing.T) {
+	testCases := []struct {
+		name        string
+		round       string
+		expectError bool
+		expectedMsg string
+		expectedVal uint64
+		description string
+	}{
+		{
+			name:        "empty round parameter",
+			round:       "",
+			expectError: true,
+			expectedMsg: "round parameter is required",
+			description: "empty round should return error",
+		},
+		{
+			name:        "invalid format - non-numeric",
+			round:       "abc",
+			expectError: true,
+			expectedMsg: "invalid round number",
+			description: "non-numeric round should return error",
+		},
+		{
+			name:        "invalid format - negative",
+			round:       "-1",
+			expectError: true,
+			expectedMsg: "invalid round number",
+			description: "negative round should return error",
+		},
+		{
+			name:        "invalid format - decimal",
+			round:       "1.5",
+			expectError: true,
+			expectedMsg: "invalid round number",
+			description: "decimal round should return error",
+		},
+		{
+			name:        "extremely large number - parse error",
+			round:       "999999999999999999999999999999999999999999999999999999999999999999999999",
+			expectError: true,
+			expectedMsg: "invalid round number",
+			description: "extremely large round (parse error) should return error",
+		},
+		{
+			name:        "large but parseable number exceeding reasonable max",
+			round:       "1152921504606846977", // 2^60 + 1
+			expectError: true,
+			expectedMsg: "exceeds maximum allowed value",
+			description: "round exceeding reasonable maximum should return error",
+		},
+		{
+			name:        "valid round number",
+			round:       "1",
+			expectError: false,
+			expectedVal: 1,
+			description: "valid round should parse successfully",
+		},
+		{
+			name:        "valid large round number",
+			round:       "1152921504606846976", // 2^60 (max allowed)
+			expectError: false,
+			expectedVal: 1152921504606846976,
+			description: "valid large round at maximum should parse successfully",
+		},
+		{
+			name:        "zero round",
+			round:       "0",
+			expectError: false,
+			expectedVal: 0,
+			description: "zero round should parse successfully",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Create a chi router and request
+			r := chi.NewRouter()
+			r.Get("/test/{round}", func(w http.ResponseWriter, r *http.Request) {
+				round, err := readRound(r)
+				if tc.expectError {
+					require.Error(t, err, tc.description)
+					if tc.expectedMsg != "" {
+						require.Contains(t, err.Error(), tc.expectedMsg, tc.description)
+					}
+				} else {
+					require.NoError(t, err, tc.description)
+					require.Equal(t, tc.expectedVal, round, tc.description)
+				}
+			})
+
+			req := httptest.NewRequest("GET", "/test/"+tc.round, nil)
+			w := httptest.NewRecorder()
+			r.ServeHTTP(w, req)
+		})
+	}
+}
+
+func TestReadRoundDirect(t *testing.T) {
+	// Test empty round parameter
+	r := chi.NewRouter()
+	r.Get("/test/{round}", func(w http.ResponseWriter, r *http.Request) {
+		round, err := readRound(r)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "round parameter is required")
+		require.Equal(t, uint64(0), round)
+	})
+	req := httptest.NewRequest("GET", "/test/", nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+
+	// Test valid round
+	r = chi.NewRouter()
+	r.Get("/test/{round}", func(w http.ResponseWriter, r *http.Request) {
+		round, err := readRound(r)
+		require.NoError(t, err)
+		require.Equal(t, uint64(123), round)
+	})
+	req = httptest.NewRequest("GET", "/test/123", nil)
+	w = httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+
+	// Test invalid round
+	r = chi.NewRouter()
+	r.Get("/test/{round}", func(w http.ResponseWriter, r *http.Request) {
+		round, err := readRound(r)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "invalid round number")
+		require.Equal(t, uint64(0), round)
+	})
+	req = httptest.NewRequest("GET", "/test/abc", nil)
+	w = httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	
+	// Test round exceeding maximum
+	maxRound := strconv.FormatUint(uint64(1<<60)+1, 10)
+	r = chi.NewRouter()
+	r.Get("/test/{round}", func(w http.ResponseWriter, r *http.Request) {
+		round, err := readRound(r)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "exceeds maximum allowed value")
+		require.Equal(t, uint64(0), round)
+	})
+	req = httptest.NewRequest("GET", "/test/"+maxRound, nil)
+	w = httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+}