For historical reasons java on macOS may pick up system proxies by default.
Tests that do not want to be affected by proxy selections should set up a default ProxySelector that always return NO_PROXY, or open URL connection specifying NO_PROXY.

Affected test:

sun/security/krb5/auto/HttpNegotiateServer.java

java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:476)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:218)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:200)
at java.net.Socket.connect(Socket.java:606)
at java.net.Socket.connect(Socket.java:555)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:499)
at sun.net.www.http.HttpClient$1.run(HttpClient.java:551)
at sun.net.www.http.HttpClient$1.run(HttpClient.java:549)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.http.HttpClient.privilegedOpenServer(HttpClient.java:548)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:589)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:280)
at sun.net.www.http.HttpClient.New(HttpClient.java:375)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1264)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1211)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1078)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1012)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1623)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1551)
at HttpNegotiateServer.test6578647(HttpNegotiateServer.java:241)
at HttpNegotiateServer.main(HttpNegotiateServer.java:208)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.lang.Thread.run(Thread.java:750)


Expecting to succeed when executing with the the logged in subject.
java.lang.RuntimeException: java.net.ConnectException: Connection refused (Connection refused)
at HttpNegotiateServer.testConnect(HttpNegotiateServer.java:286)
at HttpNegotiateServer$3.run(HttpNegotiateServer.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at HttpNegotiateServer.test8077155(HttpNegotiateServer.java:369)
at HttpNegotiateServer.main(HttpNegotiateServer.java:220)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.lang.Thread.run(Thread.java:750)
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:476)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:218)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:200)
at java.net.Socket.connect(Socket.java:606)
at java.net.Socket.connect(Socket.java:555)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:499)
at sun.net.www.http.HttpClient$1.run(HttpClient.java:551)
at sun.net.www.http.HttpClient$1.run(HttpClient.java:549)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.http.HttpClient.privilegedOpenServer(HttpClient.java:548)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:589)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:280)
at sun.net.www.http.HttpClient.New(HttpClient.java:375)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1264)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1211)
at sun.net.www.protocol.http.HttpURLConnection$6.run(HttpURLConnection.java:1068)
at sun.net.www.protocol.http.HttpURLConnection$6.run(HttpURLConnection.java:1066)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessController.doPrivilegedWithCombiner(AccessController.java:784)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1065)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1012)
at HttpNegotiateServer.testConnect(HttpNegotiateServer.java:276)
... 11 more