Add unit test for Interface and catch uninitialized usage of it.

src/main/c/src/Interface.c

@@ -8,7 +8,7 @@
 
 jobject wrapInterface(JNIEnv *env, const struct libusb_interface *iface)
 {
-    WRAP_POINTER(env, iface, "Interface", "pointer");
+    WRAP_POINTER(env, iface, "Interface", "interfacePointer");
 }
 
 jobjectArray wrapInterfaces(JNIEnv *env, int count,
@@ -27,7 +27,7 @@ jobjectArray wrapInterfaces(JNIEnv *env, int count,
 
 struct libusb_interface *unwrapInterface(JNIEnv *env, jobject obj)
 {
-    UNWRAP_POINTER(env, obj, struct libusb_interface*, "pointer");
+    UNWRAP_POINTER(env, obj, struct libusb_interface*, "interfacePointer");
 }
 
 JNIEXPORT jshort JNICALL METHOD_NAME(Interface, numAltsetting)
@@ -35,7 +35,9 @@ JNIEXPORT jshort JNICALL METHOD_NAME(Interface, numAltsetting)
     JNIEnv *env, jobject this
 )
 {
-    return (jshort) unwrapInterface(env, this)->num_altsetting;
+    struct libusb_interface* interface = unwrapInterface(env, this);
+    if (!interface) return 0;
+    return (jshort) interface->num_altsetting;
 }
 
 JNIEXPORT jobjectArray JNICALL METHOD_NAME(Interface, altsetting)
@@ -44,6 +46,7 @@ JNIEXPORT jobjectArray JNICALL METHOD_NAME(Interface, altsetting)
 )
 {
     struct libusb_interface* interface = unwrapInterface(env, this);
+    if (!interface) return NULL;
     return wrapInterfaceDescriptors(env, interface->num_altsetting,
         interface->altsetting);
 }

src/main/java/de/ailis/usb4java/libusb/Interface.java

@@ -21,7 +21,7 @@ import org.apache.commons.lang3.builder.HashCodeBuilder;
 public final class Interface
 {
     /** The native pointer to the descriptor structure. */
-    private long pointer;
+    private long interfacePointer;
 
     /**
      * Package-private constructor to prevent manual instantiation. Interfaces 
@@ -39,7 +39,7 @@ public final class Interface
      */
     public long getPointer()
     {
-        return this.pointer;
+        return this.interfacePointer;
     }
         
     /**
@@ -88,7 +88,7 @@ public final class Interface
     @Override
     public int hashCode()
     {
-        return new HashCodeBuilder().append(this.pointer).toHashCode();
+        return new HashCodeBuilder().append(this.interfacePointer).toHashCode();
     }
 
     @Override
@@ -97,7 +97,7 @@ public final class Interface
         if (this == obj) return true;
         if (obj == null || getClass() != obj.getClass()) return false;
         final Interface other = (Interface) obj;
-        return this.pointer == other.pointer;
+        return this.interfacePointer == other.interfacePointer;
     }
     
     @Override

src/test/java/de/ailis/usb4java/libusb/InterfaceTest.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2013 Klaus Reimer <k@ailis.de>
+ * See LICENSE.md for licensing information.
+ */
+
+package de.ailis.usb4java.libusb;
+
+import static de.ailis.usb4java.test.UsbAssume.assumeUsbTestsEnabled;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Tests the {@link Interface} class.
+ * 
+ * @author Klaus Reimer (k@ailis.de)
+ */
+public class InterfaceTest
+{
+    /** The test subject. */
+    private Interface descriptor;
+
+    /**
+     * Setup test.
+     */
+    @Before
+    public void setUp()
+    {
+        assumeUsbTestsEnabled();
+        LibUsb.init(null);
+        this.descriptor = new Interface();
+    }
+    
+    /**
+     * Tear down test.
+     */
+    @After    
+    public void tearDown()
+    {
+        LibUsb.exit(null);
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link Interface#altsetting()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedAltsetting()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.altsetting();
+    }
+
+    /**
+     * Tests uninitialized access to
+     * {@link Interface#numAltsetting()}
+     */
+    @Test(expected = IllegalStateException.class)
+    public void testUninitializedDescriptorType()
+    {
+        assumeUsbTestsEnabled();
+        this.descriptor.numAltsetting();
+    }
+}