There are tests which are depending on internal APIs, and those tests are designed for testing internal APIs. These tests should work with modular system

Test depending on sun.net.www.MessageHeader and sun.net.www.protocol.file.FileURLConnection
tests/jdk/java/net/URLConnection/B5052093.java

Test depending on sun.net.www.content.text.PlainTextInputStream and sun.net.www.MessageHeader
tests/jdk/java/net/URLConnection/HandleContentTypeWithAttrs.java

Test depending on sun.net.ftp.FtpLoginException
tests/jdk/sun/net/ftp/B6427768.java

Test depending on sun.net.idn.Punycode
tests/jdk/sun/net/idn/PunycodeTest.java

Test depending on sun.net.idn.StringPrep and sun.text.normalizer.UCharacterIterator
tests/jdk/sun/net/idn/TestStringPrep.java

Tests depending on sun.net.spi.nameservice.NameService and sun.net.spi.nameservice.NameServiceDescriptor
tests/jdk/sun/net/InetAddress/nameservice/chaining/Providers.java
tests/jdk/sun/net/InetAddress/nameservice/deadlock/Hang.java
tests/jdk/sun/net/InetAddress/nameservice/simple/CacheTest.java
tests/jdk/sun/net/InetAddress/nameservice/simple/DefaultCaching.java

Test depending on sun.net.TelnetOutputStream
tests/jdk/sun/net/TelnetTest.java

Test depending on sun.net.www.HeaderParser
tests/jdk/sun/net/www/EmbeddedEquals.java

Test depending on sun.net.www.HeaderParser andsun.net.www.MessageHeader
tests/jdk/sun/net/www/HeaderTests.java

Test depending on sun.net.ProgressMeteringPolicy , sun.net.ProgressListener , sun.net.ProgressMonitor and sun.net.ProgressEvent
tests/jdk/sun/net/www/http/ChunkedInputStream/ChunkedEncodingWithProgressMonitorTest.java

Tests depending on sun.net.www.http.HttpClient
tests/jdk/sun/net/www/http/HttpClient/GetProxyPort.java
tests/jdk/sun/net/www/http/HttpClient/ImplicitFileName.java
tests/jdk/sun/net/www/http/HttpClient/IsKeepingAlive.java
tests/jdk/sun/net/www/http/HttpClient/OpenServer.java

Test depending on sun.net.www.MessageHeader
tests/jdk/sun/net/www/MessageHeaderTest.java

Tests depending on sun.net.www.ParseUtil
tests/jdk/sun/net/www/ParseUtil_4922813.java
tests/jdk/sun/net/www/ParseUtil_6274990.java
tests/jdk/sun/net/www/ParseUtil_6306697.java
tests/jdk/sun/net/www/ParseUtil_6380332.java
tests/jdk/sun/net/www/ParseUtil_6478588.java

Test depending on sun.net.www.protocol.http.HttpURLConnection
tests/jdk/sun/net/www/protocol/http/ZoneId.java

Test depending on com.sun.net.ssl.internal.www.protocol.https.HttpsURLConnectionOldImpl and sun.net.www.protocol.https.HttpsURLConnectionImpl
tests/jdk/sun/net/www/protocol/https/HttpsURLConnection/CheckMethods.java

Test depending on sun.applet.AppletClassLoader
tests/jdk/sun/misc/URLClassPath/ClassnameCharTest.java