Update test to assert on current behaviour

test/integration/client-side-operations-timeout/client_side_operations_timeout.unit.test.ts

@@ -33,17 +33,20 @@ describe('CSOT spec unit tests', function () {
       client = this.configuration.newClient({ timeoutMS: 1000 });
       // Spy on connection checkout and pull options argument
       const checkoutSpy = sinon.spy(ConnectionPool.prototype, 'checkOut');
-      const remainingTimeSpy = sinon.spy(Timeout.prototype, 'remainingTime', ['get']);
+      const selectServerSpy = sinon.spy(Topology.prototype, 'selectServer');
+      const expiresSpy = sinon.spy(Timeout, 'expires');
 
       await client.db('db').collection('collection').insertOne({ x: 1 });
-      const remainingTimeFirstCall = remainingTimeSpy.get.firstCall;
 
       expect(checkoutSpy).to.have.been.calledOnce;
       expect(checkoutSpy.firstCall.args[0].timeout).to.exist;
-      expect(checkoutSpy.firstCall.args[0].timeout.duration).to.be.approximately(
-        remainingTimeFirstCall.returnValue,
-        3
+      // Check that we passed through the timeout
+      expect(checkoutSpy.firstCall.args[0].timeout).to.equal(
+        selectServerSpy.lastCall.lastArg.timeout
       );
+
+      // Check that no more Timeouts are constructed after we enter checkout
+      expect(!expiresSpy.calledAfter(checkoutSpy));
     });
 
     it('If timeoutMS is not set for an operation, waitQueueTimeoutMS should apply to connection checkout after a server has been selected.', async function () {