turns out I couldn't use it, but since I wrote it, I'm committing it.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@25774 71c3de6d-444a-0410-be80-ed276b4c234a

test/src/main/java/org/jvnet/hudson/test/DefaultConstructorChecker.java

+package org.jvnet.hudson.test;
+
+import junit.framework.TestCase;
+
+/**
+ * Tests that the specified class has the default constructor.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+public class DefaultConstructorChecker extends TestCase {
+    private final Class clazz;
+
+    public DefaultConstructorChecker(Class clazz) {
+        this.clazz = clazz;
+        setName(clazz.getName()+".verifyDefaultConstructor");
+    }
+
+    @Override
+    protected void runTest() throws Throwable {
+        try {
+            clazz.getConstructor();
+        } catch (NoSuchMethodException e) {
+            throw new Error(clazz+" must have the default constructor",e);
+        } catch (SecurityException e) {
+            throw new Error(clazz+" must have the default constructor",e);
+        }
+    }
+}