test(NODE-6492): add integration tests for transaction write concern behavior

Author: nbbeeken

test/integration/transactions/transactions.prose.test.ts

@@ -0,0 +1,49 @@
+import { expect } from 'chai';
+
+import { type MongoClient } from '../../mongodb';
+
+const metadata: MongoDBMetadataUI = {
+  requires: {
+    topology: '!single'
+  }
+};
+
+describe('Transactions Spec Prose', function () {
+  let client: MongoClient;
+  const started = [];
+
+  beforeEach(async function () {
+    started.length = 0;
+    client = this.configuration.newClient({}, { monitorCommands: true });
+    client.on('commandStarted', ev => started.push(ev));
+  });
+
+  afterEach(async function () {
+    await client.close();
+  });
+
+  describe('Options Inside Transaction', function () {
+    it(
+      '1.0 Write concern not inherited from collection object inside transaction.',
+      metadata,
+      async () => {
+        await client.withSession(async session => {
+          session.startTransaction();
+
+          const collection = client.db().collection('txn-test', { writeConcern: { w: 0 } });
+
+          await collection.insertOne({ n: 1 }, { session });
+
+          await session.commitTransaction();
+        });
+
+        const insertStarted = started.find(ev => ev.commandName === 'insert');
+        expect(insertStarted).to.not.have.nested.property('command.writeConcern');
+
+        // not in asked by the spec test but good to check, this is where the WC would be if it wasn't ignored.
+        const commitTransactionStarted = started.find(ev => ev.commandName === 'commitTransaction');
+        expect(commitTransactionStarted).to.not.have.nested.property('command.writeConcern');
+      }
+    );
+  });
+});