Add unit test for MDC restoration.

Author: sjoerdtalsma

mdc-propagation/src/test/java/nl/talsmasoftware/context/mdc/MdcManagerTest.java

@@ -15,6 +15,9 @@
  */
 package nl.talsmasoftware.context.mdc;
 
+import nl.talsmasoftware.context.Context;
+import nl.talsmasoftware.context.ContextManagers;
+import nl.talsmasoftware.context.ContextSnapshot;
 import nl.talsmasoftware.context.executors.ContextAwareExecutorService;
 import org.junit.After;
 import org.junit.Before;
@@ -46,6 +49,12 @@ public void shutdownThreadpool() {
         threadpool = null;
     }
 
+    @Before
+    @After
+    public void clearMDC() {
+        MDC.clear();
+    }
+
     private static final Callable<String> GET_MDC_ITEM = new Callable<String>() {
         public String call() {
             return MDC.get("mdc-item");
@@ -59,4 +68,21 @@ public void testMdcItemPropagation() throws ExecutionException, InterruptedExcep
         assertThat(itemValue.get(), is("Item value"));
     }
 
+    @Test
+    public void testMdcItemRestoration() throws Exception {
+        MDC.put("mdc-item", "Value 1");
+
+        ContextSnapshot snapshot = ContextManagers.createContextSnapshot();
+        assertThat("New snapshot shouldn't manipulate MDC.", GET_MDC_ITEM.call(), is("Value 1"));
+
+        MDC.put("mdc-item", "Value 2");
+        assertThat("Sanity check: MDC changed?", GET_MDC_ITEM.call(), is("Value 2"));
+
+        Context<Void> reactivation = snapshot.reactivate();
+        assertThat("MDC changed by reactivation", GET_MDC_ITEM.call(), is("Value 1"));
+
+        reactivation.close();
+        assertThat("MDC restored?", GET_MDC_ITEM.call(), is("Value 2"));
+    }
+
 }