Fix flaky tests in HTTPClientSOCKSTests (#498)

* bind to a port defined by the operating system

Author: dnadoba

Tests/AsyncHTTPClientTests/HTTPClient+SOCKSTests.swift

@@ -76,7 +76,7 @@ class HTTPClientSOCKSTests: XCTestCase {
     func testProxySOCKS() throws {
         let socksBin = try MockSOCKSServer(expectedURL: "/socks/test", expectedResponse: "it works!")
         let localClient = HTTPClient(eventLoopGroupProvider: .shared(self.clientGroup),
-                                     configuration: .init(proxy: .socksServer(host: "localhost")))
+                                     configuration: .init(proxy: .socksServer(host: "localhost", port: socksBin.port)))
 
         defer {
             XCTAssertNoThrow(try localClient.syncShutdown())
@@ -125,7 +125,7 @@ class HTTPClientSOCKSTests: XCTestCase {
     func testProxySOCKSMisbehavingServer() throws {
         let socksBin = try MockSOCKSServer(expectedURL: "/socks/test", expectedResponse: "it works!", misbehave: true)
         let localClient = HTTPClient(eventLoopGroupProvider: .shared(self.clientGroup),
-                                     configuration: .init(proxy: .socksServer(host: "localhost")))
+                                     configuration: .init(proxy: .socksServer(host: "localhost", port: socksBin.port)))
 
         defer {
             XCTAssertNoThrow(try localClient.syncShutdown())

Tests/AsyncHTTPClientTests/SOCKSTestUtils.swift

@@ -36,6 +36,10 @@ class TestSOCKSBadServerHandler: ChannelInboundHandler {
 class MockSOCKSServer {
     let channel: Channel
 
+    var port: Int {
+        self.channel.localAddress!.port!
+    }
+
     init(expectedURL: String, expectedResponse: String, misbehave: Bool = false, file: String = #file, line: UInt = #line) throws {
         let elg = MultiThreadedEventLoopGroup(numberOfThreads: 1)
         let bootstrap: ServerBootstrap
@@ -57,7 +61,7 @@ class MockSOCKSServer {
                     ])
                 }
         }
-        self.channel = try bootstrap.bind(host: "localhost", port: 1080).wait()
+        self.channel = try bootstrap.bind(host: "localhost", port: 0).wait()
     }
 
     func shutdown() throws {