added missing RunWith annotations

xds/src/test/java/io/grpc/xds/XdsLoadBalancerWithLrsTest.java

diff --git a/xds/src/test/java/io/grpc/xds/XdsLoadBalancerWithLrsTest.java b/xds/src/test/java/io/grpc/xds/XdsLoadBalancerWithLrsTest.java
index b969d93..1e54b23 100644
--- a/xds/src/test/java/io/grpc/xds/XdsLoadBalancerWithLrsTest.java
+++ b/xds/src/test/java/io/grpc/xds/XdsLoadBalancerWithLrsTest.java
@@ -63,10 +63,17 @@
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
 import org.mockito.InOrder;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
+/**
+ * Unit tests for {@link XdsLoadBalancer}, especially for interactions between
+ * {@link XdsLoadBalancer} and {@link XdsLoadReportClient}.
+ */
+@RunWith(JUnit4.class)
 public class XdsLoadBalancerWithLrsTest {
   private static final String SERVICE_AUTHORITY = "test authority";
 

xds/src/test/java/io/grpc/xds/XdsLocalityTest.java

diff --git a/xds/src/test/java/io/grpc/xds/XdsLocalityTest.java b/xds/src/test/java/io/grpc/xds/XdsLocalityTest.java
index bc9b214..8c3f965 100644
--- a/xds/src/test/java/io/grpc/xds/XdsLocalityTest.java
+++ b/xds/src/test/java/io/grpc/xds/XdsLocalityTest.java
@@ -21,7 +21,13 @@
 import com.google.common.testing.EqualsTester;
 import io.envoyproxy.envoy.api.v2.core.Locality;
 import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
 
+/**
+ * Unit tests for {@link XdsLocality}.
+ */
+@RunWith(JUnit4.class)
 public class XdsLocalityTest {
 
   @Test