fix: address code quality flags

Author: diegomarquezp

gax-java/gax-httpjson/src/test/java/com/google/api/gax/httpjson/HttpJsonCallOptionsTest.java

@@ -41,7 +41,7 @@ public class HttpJsonCallOptionsTest {
   private final HttpJsonCallOptions.Builder OPTIONS_BUILDER = HttpJsonCallOptions.newBuilder();
 
   @Test
-  public void testTracer() {
+  void testTracer() {
     ApiTracer tracer = Mockito.mock(ApiTracer.class);
     HttpJsonCallOptions options = OPTIONS_BUILDER.setTracer(tracer).build();
     assertThat(options.getTracer()).isSameInstanceAs(tracer);

gax-java/gax/src/test/java/com/google/api/gax/tracing/BaseApiTracerTest.java

@@ -29,6 +29,8 @@
  */
 package com.google.api.gax.tracing;
 
+import static com.google.common.truth.Truth.assertThat;
+
 import org.junit.jupiter.api.Test;
 
 public class BaseApiTracerTest {
@@ -161,9 +163,14 @@ public void testBatchRequestSent() {
   }
 
   @Test
-  public void testRecordResponseSize() {
-    BaseApiTracer tracer = new BaseApiTracer();
-    tracer.recordResponseSize(10);
-    // No-op, so nothing to verify.
+  void testRecordResponseSize() {
+    Throwable notExpected = null;
+    try {
+      BaseApiTracer tracer = new BaseApiTracer();
+      tracer.recordResponseSize(10);
+    } catch (Exception ex) {
+      notExpected = ex;
+    }
+    assertThat(notExpected).isNull();
   }
 }