Add ExceptionWrapper test rule

Author: kiritsuku

org.scala-refactoring.library/src/test/java/scala/tools/refactoring/tests/util/ExceptionWrapper.java

@@ -0,0 +1,30 @@
+package scala.tools.refactoring.tests.util;
+
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+import scala.tools.nsc.util.FailedInterrupt;
+
+/**
+ * In case an assertion error is caught and wrapped by another error type (as it
+ * is the case for exceptions that are thrown on the compiler thread), we need
+ * to manually unwrap them later, in order to let JUnit "see" them.
+ */
+public final class ExceptionWrapper implements TestRule {
+
+  @Override
+  public Statement apply(final Statement base, final Description description) {
+    return new Statement() {
+      @Override
+      public void evaluate() throws Throwable {
+        try {
+          base.evaluate();
+        } catch (FailedInterrupt e) {
+          // a FailedInterrupt is thrown when an exception occurs on the compiler thread
+          throw e.getCause();
+        }
+      }
+    };
+  }
+}

org.scala-refactoring.library/src/test/java/scala/tools/refactoring/tests/util/TestRules.java

@@ -8,4 +8,7 @@ public abstract class TestRules {
 
   @Rule
   public final ScalaVersionTestRule rule1 = new ScalaVersionTestRule();
+
+  @Rule
+  public final ExceptionWrapper rule2 = new ExceptionWrapper();
 }