Add test rule and property for better handling JNA if not available or in need of custom extension.

Author: raphw

byte-buddy-agent/pom.xml

@@ -18,6 +18,7 @@
         <packages.list>net.bytebuddy.agent,net.bytebuddy.agent.utility.nullability</packages.list>
         <native.compiler.32>i686-w64-mingw32-gcc</native.compiler.32>
         <native.compiler.64>x86_64-w64-mingw32-gcc</native.compiler.64>
+        <net.bytebuddy.test.jnapath/>
     </properties>
 
     <name>Byte Buddy agent</name>
@@ -89,6 +90,15 @@
             </resource>
         </resources>
         <plugins>
+            <!-- Allow for specifying a custom library path for JNA. -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>${version.plugin.surefire}</version>
+                <configuration combine.children="append">
+                    <argLine>-Djna.library.path=${net.bytebuddy.test.jnapath}</argLine>
+                </configuration>
+            </plugin>
             <!-- Create manifest file which is required for creating an OSGi bundle. -->
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>

byte-buddy-agent/src/test/java/net/bytebuddy/agent/VirtualMachineAttachmentTest.java

@@ -1,9 +1,12 @@
 package net.bytebuddy.agent;
 
 import net.bytebuddy.dynamic.ClassFileLocator;
+import net.bytebuddy.test.utility.JnaRule;
 import org.junit.After;
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TestRule;
 
 import java.io.File;
 import java.io.FileOutputStream;
@@ -20,6 +23,9 @@ public class VirtualMachineAttachmentTest {
 
     private static final String FOO = "foo";
 
+    @Rule
+    public TestRule jnaRule = new JnaRule();
+
     private File agent;
 
     @Before

byte-buddy-agent/src/test/java/net/bytebuddy/test/utility/JnaRule.java

@@ -0,0 +1,46 @@
+package net.bytebuddy.test.utility;
+
+import com.sun.jna.Library;
+import com.sun.jna.Native;
+import com.sun.jna.Platform;
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+import java.util.logging.Logger;
+
+public class JnaRule implements TestRule {
+
+    private final boolean available;
+
+    @SuppressWarnings("deprecation")
+    public JnaRule() {
+        boolean available;
+        try {
+            Native.loadLibrary((Platform.isWindows() ? "msvcrt" : "c"), CLibrary.class);
+            available = true;
+        } catch (Throwable ignored) {
+            available = false;
+        }
+        this.available = available;
+    }
+
+    public Statement apply(Statement base, Description description) {
+        return available
+                ? base
+                : new NoOpStatement();
+    }
+
+    private static class NoOpStatement extends Statement {
+
+        public void evaluate() {
+            Logger.getLogger("net.bytebuddy").info("Omitting test case: JNA not available");
+        }
+    }
+
+    public interface CLibrary extends Library {
+
+        @SuppressWarnings("unused")
+        void printf(String format, Object... args);
+    }
+}