test: improve dns lookup coverage

Adding tests covering promises-related code paths.

PR-URL: #30777
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/parallel/test-dns-lookup-promises.js

@@ -0,0 +1,139 @@
+// Flags: --expose-internals
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { internalBinding } = require('internal/test/binding');
+const cares = internalBinding('cares_wrap');
+
+// Stub `getaddrinfo` to proxy its call dynamic stub. This has to be done before
+// we load the `dns` module to guarantee that the `dns` module uses the stub.
+let getaddrinfoStub = null;
+cares.getaddrinfo = (req) => getaddrinfoStub(req);
+
+const dnsPromises = require('dns').promises;
+
+function getaddrinfoNegative() {
+  return function getaddrinfoNegativeHandler(req) {
+    const originalReject = req.reject;
+    req.resolve = common.mustNotCall();
+    req.reject = common.mustCall(originalReject);
+    req.oncomplete(internalBinding('uv').UV_ENOMEM);
+  };
+}
+
+function getaddrinfoPositive(addresses) {
+  return function getaddrinfo_positive(req) {
+    const originalResolve = req.resolve;
+    req.reject = common.mustNotCall();
+    req.resolve = common.mustCall(originalResolve);
+    req.oncomplete(null, addresses);
+  };
+}
+
+async function lookupPositive() {
+  [
+    {
+      stub: getaddrinfoPositive(['::1']),
+      factory: () => dnsPromises.lookup('example.com'),
+      expectation: { address: '::1', family: 6 }
+    },
+    {
+      stub: getaddrinfoPositive(['127.0.0.1']),
+      factory: () => dnsPromises.lookup('example.com'),
+      expectation: { address: '127.0.0.1', family: 4 }
+    },
+    {
+      stub: getaddrinfoPositive(['127.0.0.1'], { family: 4 }),
+      factory: () => dnsPromises.lookup('example.com'),
+      expectation: { address: '127.0.0.1', family: 4 }
+    },
+    {
+      stub: getaddrinfoPositive(['some-address']),
+      factory: () => dnsPromises.lookup('example.com'),
+      expectation: { address: 'some-address', family: 0 }
+    },
+    {
+      stub: getaddrinfoPositive(['some-address2']),
+      factory: () => dnsPromises.lookup('example.com', { family: 6 }),
+      expectation: { address: 'some-address2', family: 6 }
+    }
+  ].forEach(async ({ stub, factory, expectation }) => {
+    getaddrinfoStub = stub;
+    assert.deepStrictEqual(await factory(), expectation);
+  });
+}
+
+async function lookupNegative() {
+  getaddrinfoStub = getaddrinfoNegative();
+  const expected = {
+    code: 'ENOMEM',
+    hostname: 'example.com',
+    syscall: 'getaddrinfo'
+  };
+  return assert.rejects(dnsPromises.lookup('example.com'), expected);
+}
+
+async function lookupallPositive() {
+  [
+    {
+      stub: getaddrinfoPositive(['::1', '::2']),
+      factory: () => dnsPromises.lookup('example', { all: true }),
+      expectation: [
+        { address: '::1', family: 6 },
+        { address: '::2', family: 6 }
+      ]
+    },
+    {
+      stub: getaddrinfoPositive(['::1', '::2']),
+      factory: () => dnsPromises.lookup('example', { all: true, family: 4 }),
+      expectation: [
+        { address: '::1', family: 4 },
+        { address: '::2', family: 4 }
+      ]
+    },
+    {
+      stub: getaddrinfoPositive(['127.0.0.1', 'some-address']),
+      factory: () => dnsPromises.lookup('example', { all: true }),
+      expectation: [
+        { address: '127.0.0.1', family: 4 },
+        { address: 'some-address', family: 0 }
+      ]
+    },
+    {
+      stub: getaddrinfoPositive(['127.0.0.1', 'some-address']),
+      factory: () => dnsPromises.lookup('example', { all: true, family: 6 }),
+      expectation: [
+        { address: '127.0.0.1', family: 6 },
+        { address: 'some-address', family: 6 }
+      ]
+    },
+    {
+      stub: getaddrinfoPositive([]),
+      factory: () => dnsPromises.lookup('example', { all: true }),
+      expectation: []
+    }
+  ].forEach(async ({ stub, factory, expectation }) => {
+    getaddrinfoStub = stub;
+    assert.deepStrictEqual(await factory(), expectation);
+  });
+}
+
+async function lookupallNegative() {
+  getaddrinfoStub = getaddrinfoNegative();
+  const expected = {
+    code: 'ENOMEM',
+    hostname: 'example.com',
+    syscall: 'getaddrinfo'
+  };
+  return assert.rejects(dnsPromises.lookup('example.com', { all: true }),
+                        expected);
+}
+
+(async () => {
+  await Promise.all([
+    lookupPositive(),
+    lookupNegative(),
+    lookupallPositive(),
+    lookupallNegative()
+  ]).then(common.mustCall());
+})();