package com.atlassian.plugin.util;
   
   import org.junit.After;
   import org.junit.Before;
   import org.junit.Test;
   
   import java.net.URISyntaxException;
   
   import static org.junit.Assert.assertNull;
  import static org.junit.Assert.assertSame;
  
  public class TestClassLoaderStack {
  
      private ClassLoader mainLoader;
  
      @Before
      public void setUp() throws Exception {
          mainLoader = Thread.currentThread().getContextClassLoader();
      }
  
      @After
      public void tearDown() throws Exception {
          Thread.currentThread().setContextClassLoader(mainLoader);
      }
  
      @Test
      public void testThreadClassLoaderIsReplacedAndRestored() throws URISyntaxException {
          ClassLoader pluginLoader1 = new MockClassLoader();
          ClassLoader pluginLoader2 = new MockClassLoader();
  
          ClassLoaderStack.push(pluginLoader1);
          assertSame(pluginLoader1, Thread.currentThread().getContextClassLoader());
          ClassLoaderStack.push(pluginLoader2);
          assertSame(pluginLoader2, Thread.currentThread().getContextClassLoader());
          ClassLoaderStack.pop();
          assertSame(pluginLoader1, Thread.currentThread().getContextClassLoader());
          ClassLoaderStack.pop();
          assertSame(mainLoader, Thread.currentThread().getContextClassLoader());
      }
  
      @Test
      public void testPopReturnsPreviousContextClassLoader() throws Exception {
          ClassLoader pluginLoader1 = new MockClassLoader();
          ClassLoader pluginLoader2 = new MockClassLoader();
  
          ClassLoaderStack.push(pluginLoader1);
          assertSame(pluginLoader1, Thread.currentThread().getContextClassLoader());
          ClassLoaderStack.push(pluginLoader2);
          assertSame(pluginLoader2, Thread.currentThread().getContextClassLoader());
          ClassLoader previous = ClassLoaderStack.pop();
          assertSame(pluginLoader2, previous);
          assertSame(pluginLoader1, Thread.currentThread().getContextClassLoader());
          previous = ClassLoaderStack.pop();
          assertSame(pluginLoader1, previous);
          assertSame(mainLoader, Thread.currentThread().getContextClassLoader());
      }
  
      @Test
      public void testPushAndPopHandleNull() throws Exception {
          // popping with empty stack should return null
          assertNull(ClassLoaderStack.pop());
          // pushing null should be a no-op
          ClassLoaderStack.push(null);
          assertSame(mainLoader, Thread.currentThread().getContextClassLoader());
          assertNull(ClassLoaderStack.pop());
      }
  
      public static class MockClassLoader extends ClassLoader {
      }
  }