feat(MongoMemoryReplSet): add named error for "count" assertion

docs/guides/error-warning-details.md

@@ -82,3 +82,10 @@ Example: `Assert failed - no custom error`
 
 Details:  
 This Error gets thrown when no custom error to `assertion` is given, this should never happen
+
+## ReplsetCountLowError
+
+Example: `ReplSet Count needs to be 1 or higher! (specified count: "${count}")`
+
+Details:  
+ReplSet count (like `new MongoMemoryReplSet({ replSet: { count: 0 } })`) needs to be `1` or higher

packages/mongodb-memory-server-core/src/MongoMemoryReplSet.ts

@@ -24,6 +24,7 @@ import { SpawnOptions } from 'child_process';
 import {
   AuthNotObjectError,
   InstanceInfoError,
+  ReplsetCountLowError,
   StateError,
   WaitForPrimaryTimeoutError,
 } from './util/errors';
@@ -251,7 +252,7 @@ export class MongoMemoryReplSet extends EventEmitter implements ManagerAdvanced
     };
     this._replSetOpts = { ...defaults, ...val };
 
-    assertion(this._replSetOpts.count > 0, new Error('ReplSet Count needs to be 1 or higher!'));
+    assertion(this._replSetOpts.count > 0, new ReplsetCountLowError(this._replSetOpts.count));
 
     if (typeof this._replSetOpts.auth === 'object') {
       this._replSetOpts.auth = authDefault(this._replSetOpts.auth);

packages/mongodb-memory-server-core/src/__tests__/MongoMemoryReplSet.test.ts

@@ -7,7 +7,7 @@ import { MongoClient } from 'mongodb';
 import MongoMemoryServer from '../MongoMemoryServer';
 import * as utils from '../util/utils';
 import { MongoMemoryInstanceOpts } from '../util/MongoInstance';
-import { StateError, WaitForPrimaryTimeoutError } from '../util/errors';
+import { ReplsetCountLowError, StateError, WaitForPrimaryTimeoutError } from '../util/errors';
 import { assertIsError } from './testUtils/test_utils';
 
 jest.setTimeout(100000); // 10s
@@ -78,6 +78,8 @@ describe('single server replset', () => {
       new MongoMemoryReplSet({ replSet: { count: 0 } });
       fail('Expected "new MongoMemoryReplSet" to throw an error');
     } catch (err) {
+      expect(err).toBeInstanceOf(ReplsetCountLowError);
+      expect(err).toHaveProperty('count', 0);
       assertIsError(err);
       expect(err.message).toMatchSnapshot();
     }
@@ -422,6 +424,8 @@ describe('MongoMemoryReplSet', () => {
         replSet.replSetOpts = { count: 0 };
         fail('Expected assignment of "replSet.instanceOpts" to fail');
       } catch (err) {
+        expect(err).toBeInstanceOf(ReplsetCountLowError);
+        expect(err).toHaveProperty('count', 0);
         assertIsError(err);
         expect(err.message).toMatchSnapshot();
       }

packages/mongodb-memory-server-core/src/__tests__/__snapshots__/MongoMemoryReplSet.test.ts.snap

@@ -2,7 +2,7 @@
 
 exports[`MongoMemoryReplSet "_waitForPrimary" should throw an error if timeout is reached 1`] = `"{\\"timeout\\":1}"`;
 
-exports[`MongoMemoryReplSet getters & setters setter of "replSetOpts" should throw an error if count is 1 or above 1`] = `"ReplSet Count needs to be 1 or higher!"`;
+exports[`MongoMemoryReplSet getters & setters setter of "replSetOpts" should throw an error if count is 1 or above 1`] = `"ReplSet Count needs to be 1 or higher! (specified count: \\"0\\")"`;
 
 exports[`MongoMemoryReplSet getters & setters state errors setter of "binaryOpts" should throw an error if state is not "stopped" 1`] = `
 "Incorrect State for operation: \\"init\\", allowed States: \\"[stopped]\\"
@@ -36,7 +36,7 @@ This may be because of using a v6.x way of calling functions, look at the follow
 https://nodkz.github.io/mongodb-memory-server/docs/guides/migrate7#no-function-other-than-start-create-ensureinstance-will-be-starting-anything"
 `;
 
-exports[`single server replset "new" should throw an error if replSet count is 0 or less 1`] = `"ReplSet Count needs to be 1 or higher!"`;
+exports[`single server replset "new" should throw an error if replSet count is 0 or less 1`] = `"ReplSet Count needs to be 1 or higher! (specified count: \\"0\\")"`;
 
 exports[`single server replset "start" should throw an error if _state is not "stopped" 1`] = `
 "Incorrect State for operation: \\"running\\", allowed States: \\"[stopped]\\"

packages/mongodb-memory-server-core/src/util/errors.ts

@@ -124,3 +124,9 @@ export class AssertionFallbackError extends Error {
     super('Assert failed - no custom error');
   }
 }
+
+export class ReplsetCountLowError extends Error {
+  constructor(public count: number) {
+    super(`ReplSet Count needs to be 1 or higher! (specified count: "${count}")`);
+  }
+}