test: common: Fix flaky FinalizeTest

Adding pressure to the GC just by creating new objects may not enough;
test test failed sporadically.

Now, let's forcibly call System.gc() every 500ms as well.

Lastly, ignore all lines not related to unix sockets, if possible.

Author: kohlschuetter

junixsocket-common/src/test/java/org/newsclub/net/unix/FinalizeTestClient.java

@@ -62,8 +62,14 @@ public static void main(String[] args) throws Exception {
 
     // create some pressure on GC
     List<String> list = new ArrayList<>();
+    long nextGc = System.currentTimeMillis() + 500;
     while (true) {
       list.add(new String("junixsocket".getBytes(StandardCharsets.UTF_8), StandardCharsets.UTF_8));
+      long now = System.currentTimeMillis();
+      if (now >= nextGc) {
+        nextGc = now + 500;
+        System.gc(); // NOPMD
+      }
     }
   }
 }

junixsocket-common/src/test/java/org/newsclub/net/unix/domain/FinalizeTest.java

@@ -18,7 +18,6 @@
 package org.newsclub.net.unix.domain;
 
 import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.junit.jupiter.api.Assumptions.assumeFalse;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
 import java.io.BufferedReader;
@@ -27,8 +26,8 @@
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Iterator;
 import java.util.List;
-import java.util.Objects;
 
 import org.newsclub.net.unix.AFSocketCapability;
 import org.newsclub.net.unix.AFSocketCapabilityRequirement;
@@ -67,12 +66,29 @@ private static List<String> lsofUnixSockets(long pid) throws IOException, TestAb
     try (BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream(), Charset
         .defaultCharset()))) {
       String l;
+
+      boolean hasUnix = false;
+
       while ((l = in.readLine()) != null) {
         lines.add(l);
+        if (!hasUnix && l.contains("unix")) {
+          hasUnix = true;
+        }
         if (l.contains("busybox")) {
           assumeTrue(false, "incompatible lsof binary");
         }
       }
+
+      if (hasUnix) {
+        // if "lsof" returns a "unix" identifier, focus on those lines specifically.
+        for (Iterator<String> it = lines.iterator(); it.hasNext();) {
+          String line = it.next();
+          if (!line.contains("unix")) {
+            it.remove();
+          }
+        }
+      }
+
       p.waitFor();
     } finally {
       p.destroy();
@@ -114,9 +130,8 @@ protected void postRunCheck(Process process, Object linesBeforeObj) throws TestA
         }
       }
 
-      assumeFalse(Objects.requireNonNull(linesAfter).isEmpty(), "lsof may fail to return anything");
-
-      if (linesAfter != null && linesBefore != null) {
+      if (linesAfter != null && linesBefore != null && !linesBefore.isEmpty() && !linesAfter
+          .isEmpty()) {
         if (linesAfter.size() >= linesBefore.size()) {
           System.err.println("lsof: Unexpected output");
           System.err.println("lsof: Output before: " + linesBefore);

src/site/markdown/changelog.md

@@ -18,6 +18,7 @@ artifact (`<type>pom</type>`); see [Add junixsocket to your project](dependency.
 - Fix duplicate file descriptors being received sporadically for non-blocking sockets and upon error
 - Fix a flaky selftest when VSOCK is not supported
 - Fix a flaky selftest with GraalvM 17
+- Fix a flaky selftest with old-style finalizers
 - Improve interoperability with exotic Linux/Java combinations
 - Add support for loongarch64 Linux
 - Add more tests