fix(NODE-4254): allow csfle to be dynamically required (#3260)

Author: durran

.evergreen/config.yml

@@ -1630,7 +1630,7 @@ tasks:
       - func: bootstrap mongo-orchestration
         vars:
           VERSION: latest
-          TOPOLOGY: server
+          TOPOLOGY: replica_set
       - func: bootstrap kms servers
       - func: run custom csfle tests
   - name: test-latest-server-noauth

.evergreen/generate_evergreen_tasks.js

@@ -512,7 +512,7 @@ oneOffFuncAsTasks.push({
       func: 'bootstrap mongo-orchestration',
       vars: {
         VERSION: 'latest',
-        TOPOLOGY: 'server'
+        TOPOLOGY: 'replica_set'
       }
     },
     { func: 'bootstrap kms servers' },

src/encrypter.ts

@@ -124,9 +124,15 @@ export class Encrypter {
 
   static checkForMongoCrypt(): void {
     let mongodbClientEncryption = undefined;
+    // Ensure you always wrap an optional require in the try block NODE-3199
     try {
-      // Ensure you always wrap an optional require in the try block NODE-3199
-      mongodbClientEncryption = require('mongodb-client-encryption');
+      // Note (NODE-4254): This is to get around the circular dependency between
+      // mongodb-client-encryption and the driver in the test scenarios.
+      if (process.env.MONGODB_CLIENT_ENCRYPTION_OVERRIDE) {
+        mongodbClientEncryption = require(process.env.MONGODB_CLIENT_ENCRYPTION_OVERRIDE);
+      } else {
+        mongodbClientEncryption = require('mongodb-client-encryption');
+      }
     } catch (err) {
       throw new MongoMissingDependencyError(
         'Auto-encryption requested, but the module is not installed. ' +