test(NODE-6910): sync initial-dns-seedlist-discovery spec tests and unskip runner

test/integration/initial-dns-seedlist-discovery/initial_dns_seedlist_discovery.spec.test.ts

@@ -4,7 +4,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import { promisify } from 'util';
 
-import { HostAddress, MongoClient } from '../../mongodb';
+import { HostAddress, MongoClient, resolveSRVRecord } from '../../mongodb';
 
 function makeTest(test, topology) {
   let client;
@@ -17,25 +17,30 @@ function makeTest(test, topology) {
   });
 
   it(test.comment, async function () {
-    this.test.skipReason =
-      'TODO(NODE-3757): These tests require specific environment setups, also the error cases need better assertions';
-    return this.skip();
     if (topology === 'replica-set' && this.configuration.topologyType !== 'ReplicaSetWithPrimary') {
-      return this.skip();
+      this.skip();
     }
 
-    if (topology === 'sharded' && this.configuration.topologyType !== 'sharded') {
-      return this.skip();
+    if (topology === 'sharded' && this.configuration.topologyType !== 'Sharded') {
+      this.skip();
     }
 
-    if (topology === 'load-balanced' && this.configuration.topologyType !== 'load-balanced') {
-      return this.skip();
+    if (topology === 'load-balanced' && this.configuration.topologyType !== 'LoadBalanced') {
+      this.skip();
     }
 
     let thrownError;
+    let resolvedSeeds: string[] | undefined;
     try {
       client = new MongoClient(test.uri, { serverSelectionTimeoutMS: 2000, tls: false });
-      await client.connect();
+      if (test.ping === false) {
+        // The spec forbids running a "ping" for these tests, and the resolved hosts may not be
+        // reachable, so only resolve (and validate) the SRV record without connecting.
+        const resolved = await resolveSRVRecord(client.options);
+        resolvedSeeds = resolved.map(h => h.toString());
+      } else {
+        await client.connect();
+      }
     } catch (error) {
       thrownError = error;
     }
@@ -45,6 +50,14 @@ function makeTest(test, topology) {
       return; // Nothing more to test...
     }
 
+    if (test.ping === false) {
+      expect(thrownError).to.not.exist;
+      if (Array.isArray(test.seeds)) {
+        expect(resolvedSeeds).to.have.members(test.seeds);
+      }
+      return; // Nothing more to test, there is no topology to inspect
+    }
+
     const options = client.options;
     const hosts = Array.from(client.topology.s.description.servers.keys());
 
@@ -79,7 +92,7 @@ function makeTest(test, topology) {
     // srvMaxHost limiting happens in the topology constructor
     if (options.srvHost && test.comment.includes('srvMaxHosts')) {
       const initialSeedlist = hosts.map(h => h.toString());
-      const selectedHosts = Array.from(topology.s.description.servers.keys());
+      const selectedHosts = Array.from<string>(client.topology.s.description.servers.keys());
 
       if (typeof test.numSeeds === 'number') {
         // numSeeds: the expected number of initial seeds discovered from the SRV record.

test/spec/initial-dns-seedlist-discovery/README.md

@@ -190,6 +190,8 @@ _mongodb._tcp.test21.test.build.10gen.cc.   86400  IN SRV  27017  localhost.test
 _customname._tcp.test22.test.build.10gen.cc 86400  IN SRV  27017  localhost.test.build.10gen.cc.
 _mongodb._tcp.test23.test.build.10gen.cc.   86400  IN SRV  8000   localhost.test.build.10gen.cc.
 _mongodb._tcp.test24.test.build.10gen.cc.   86400  IN SRV  8000   localhost.test.build.10gen.cc.
+_mongodb._tcp.build.10gen.cc.               86400  IN SRV  27017  build.10gen.cc.
+_mongodb._tcp.test.build.10gen.cc.          86400  IN SRV  27017  test.build.10gen.cc.
 
 Record                                    TTL    Class   Text
 test5.test.build.10gen.cc.                86400  IN TXT  "replicaSet=repl0&authSource=thisDB"
@@ -211,6 +213,9 @@ Notes:
 - The missing `test.` sub-domain in the SRV record target for `test12` is deliberate.
 - `test22` is used to test a custom service name (`customname`).
 - `test23` and `test24` point to port 8000 (HAProxy) and are used for load-balanced tests.
+- The `build.10gen.cc` and `test.build.10gen.cc` SRV records resolve to hostnames identical to the SRV hostname and are
+    used to verify that no error is thrown when the resolver and resolved hostnames are identical and the SRV hostname
+    has three or more `.` separated parts.
 
 In our tests we have used `localhost.test.build.10gen.cc` as the domain, and then configured
 `localhost.test.build.10gen.cc` to resolve to 127.0.0.1.

test/spec/initial-dns-seedlist-discovery/replica-set/identical-hostnames-valid-four-parts.json

@@ -0,0 +1,8 @@
+{
+  "uri": "mongodb+srv://test.build.10gen.cc/",
+  "seeds": [
+    "test.build.10gen.cc:27017"
+  ],
+  "ping": false,
+  "comment": "Should not throw when SRV hostname and resolved hostname are identical and SRV hostname has four dot-separated parts."
+}

test/spec/initial-dns-seedlist-discovery/replica-set/identical-hostnames-valid-four-parts.yml

@@ -0,0 +1,5 @@
+uri: "mongodb+srv://test.build.10gen.cc/"
+seeds:
+    - test.build.10gen.cc:27017
+ping: false
+comment: Should not throw when SRV hostname and resolved hostname are identical and SRV hostname has four dot-separated parts.

test/spec/initial-dns-seedlist-discovery/replica-set/identical-hostnames-valid-three-parts.json

@@ -0,0 +1,8 @@
+{
+  "uri": "mongodb+srv://build.10gen.cc/",
+  "seeds": [
+    "build.10gen.cc:27017"
+  ],
+  "ping": false,
+  "comment": "Should not throw when SRV hostname and resolved hostname are identical and SRV hostname has three dot-separated parts."
+}

test/spec/initial-dns-seedlist-discovery/replica-set/identical-hostnames-valid-three-parts.yml

@@ -0,0 +1,5 @@
+uri: "mongodb+srv://build.10gen.cc/"
+seeds:
+    - build.10gen.cc:27017
+ping: false
+comment: Should not throw when SRV hostname and resolved hostname are identical and SRV hostname has three dot-separated parts.