Fix missed coverage

src/main/java/com/spotify/futures/CompletableFuturesExtra.java

@@ -19,8 +19,8 @@
 import com.google.common.util.concurrent.ListenableFuture;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
 import java.util.concurrent.CompletionStage;
-import java.util.concurrent.ExecutionException;
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Function;
@@ -196,16 +196,16 @@ public static void checkCompleted(CompletionStage<?> stage) {
    * @param stage a completed stage.
    * @return the value of the stage if it has one.
    * @throws IllegalStateException if the stage is not completed.
-   * @throws com.google.common.util.concurrent.UncheckedExecutionException if the future has failed
+   * @throws com.google.common.util.concurrent.UncheckedExecutionException
+   * if the future has failed with a non-runtime exception, otherwise
+   * the actual exception
    */
   public static <T> T getCompleted(CompletionStage<T> stage) {
     CompletableFuture<T> future = stage.toCompletableFuture();
     checkCompleted(future);
     try {
-      return future.get();
-    } catch (InterruptedException e) {
-      throw Throwables.propagate(e);
-    } catch (ExecutionException e) {
+      return future.join();
+    } catch (CompletionException e) {
       throw Throwables.propagate(e.getCause());
     }
   }

src/test/java/com/spotify/futures/jdk8/CompletableFuturesExtraTest.java

@@ -126,6 +126,13 @@ public void testGetCompleted() throws Exception {
     assertEquals("hello", CompletableFuturesExtra.getCompleted(future));
   }
 
+  @Test(expected = IllegalStateException.class)
+  public void testGetCompletedFails() throws Exception {
+    final CompletionStage<String> future = new CompletableFuture<String>();
+    CompletableFuturesExtra.getCompleted(future);
+    fail();
+  }
+
   @Test(expected = IllegalArgumentException.class)
   public void testDereferenceFailure() throws Exception {
     final CompletionStage<Object> future = CompletableFuturesExtra.exceptionallyCompletedFuture(new IllegalArgumentException());