refactor(network-controller): replace magic number with calculated constant

Replace the magic number 5 with a well-documented constant that explains
how the number of attempts needed to break both circuits in an RPC service
chain is calculated. This makes the test intent clearer and the calculation
explicit.

- Add DEFAULT_REQUEST_ATTEMPTS constant
- Add DEFAULT_RPC_SERVICE_ATTEMPTS_UNTIL_BREAK constant
- Add DEFAULT_RPC_CHAIN_ATTEMPTS_UNTIL_BREAK constant with documentation
- Replace all occurrences of magic number 5 with the constant

Author: cryptodev-2s

packages/network-controller/src/rpc-service/rpc-service-chain.test.ts

@@ -8,9 +8,37 @@ import nock from 'nock';
 import { useFakeTimers } from 'sinon';
 import type { SinonFakeTimers } from 'sinon';
 
-import { DEFAULT_MAX_CONSECUTIVE_FAILURES } from './rpc-service';
+import {
+  DEFAULT_MAX_CONSECUTIVE_FAILURES,
+  DEFAULT_MAX_RETRIES,
+} from './rpc-service';
 import { RpcServiceChain } from './rpc-service-chain';
 
+/**
+ * The number of fetch requests made for a single request to an RPC service, using default max
+ * retry attempts.
+ */
+const DEFAULT_REQUEST_ATTEMPTS = 1 + DEFAULT_MAX_RETRIES;
+
+/**
+ * Number of attempts required to break the circuit of an RPC service using default retry attempts
+ * and max consecutive failures.
+ *
+ * Note: This calculation and later ones assume that there is no remainder.
+ */
+const DEFAULT_RPC_SERVICE_ATTEMPTS_UNTIL_BREAK =
+  DEFAULT_MAX_CONSECUTIVE_FAILURES / DEFAULT_REQUEST_ATTEMPTS;
+
+/**
+ * Number of attempts required to break the circuit of an RPC service chain (with a single
+ * failover) that uses default retry attempts and max consecutive failures.
+ *
+ * The value is one less than double the number of attempts needed to break a single circuit
+ * because on failure of the primary, the request gets forwarded to the failover immediately.
+ */
+const DEFAULT_RPC_CHAIN_ATTEMPTS_UNTIL_BREAK =
+  2 * DEFAULT_RPC_SERVICE_ATTEMPTS_UNTIL_BREAK - 1;
+
 describe('RpcServiceChain', () => {
   let clock: SinonFakeTimers;
 
@@ -754,7 +782,7 @@ describe('RpcServiceChain', () => {
       };
       // Retry the first endpoint until its circuit breaks, then retry the
       // second endpoint until *its* circuit breaks.
-      for (let i = 0; i < 5; i++) {
+      for (let i = 0; i < DEFAULT_RPC_CHAIN_ATTEMPTS_UNTIL_BREAK; i++) {
         await expect(rpcServiceChain.request(jsonRpcRequest)).rejects.toThrow(
           expectedError,
         );
@@ -765,7 +793,7 @@ describe('RpcServiceChain', () => {
       await rpcServiceChain.request(jsonRpcRequest);
       // Do it again: retry the first endpoint until its circuit breaks, then
       // retry the second endpoint until *its* circuit breaks.
-      for (let i = 0; i < 5; i++) {
+      for (let i = 0; i < DEFAULT_RPC_CHAIN_ATTEMPTS_UNTIL_BREAK; i++) {
         await expect(rpcServiceChain.request(jsonRpcRequest)).rejects.toThrow(
           expectedError,
         );
@@ -856,7 +884,7 @@ describe('RpcServiceChain', () => {
       };
       // Retry the first endpoint until its circuit breaks, then retry the
       // second endpoint until *its* circuit breaks.
-      for (let i = 0; i < 5; i++) {
+      for (let i = 0; i < DEFAULT_RPC_CHAIN_ATTEMPTS_UNTIL_BREAK; i++) {
         await expect(rpcServiceChain.request(jsonRpcRequest)).rejects.toThrow(
           expectedError,
         );
@@ -867,7 +895,7 @@ describe('RpcServiceChain', () => {
       await rpcServiceChain.request(jsonRpcRequest);
       // Do it again: retry the first endpoint until its circuit breaks, then
       // retry the second endpoint until *its* circuit breaks.
-      for (let i = 0; i < 5; i++) {
+      for (let i = 0; i < DEFAULT_RPC_CHAIN_ATTEMPTS_UNTIL_BREAK; i++) {
         await expect(rpcServiceChain.request(jsonRpcRequest)).rejects.toThrow(
           expectedError,
         );