diff --git a/appengine/java/com/google/auth/appengine/AppEngineCredentials.java b/appengine/java/com/google/auth/appengine/AppEngineCredentials.java
index 3af489d67..16d046907 100644
--- a/appengine/java/com/google/auth/appengine/AppEngineCredentials.java
+++ b/appengine/java/com/google/auth/appengine/AppEngineCredentials.java
@@ -139,6 +139,7 @@ public static Builder newBuilder() {
     return new Builder();
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -175,6 +176,7 @@ public AppIdentityService getAppIdentityService() {
       return appIdentityService;
     }
 
+    @Override
     public AppEngineCredentials build() {
       return new AppEngineCredentials(scopes, appIdentityService);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/CloudShellCredentials.java b/oauth2_http/java/com/google/auth/oauth2/CloudShellCredentials.java
index 8574f0108..2baa77f50 100644
--- a/oauth2_http/java/com/google/auth/oauth2/CloudShellCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/CloudShellCredentials.java
@@ -115,6 +115,7 @@ public boolean equals(Object obj) {
     return this.authPort == other.authPort;
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -142,6 +143,7 @@ public int getAuthPort() {
       return authPort;
     }
 
+    @Override
     public CloudShellCredentials build() {
       return new CloudShellCredentials(authPort);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/ComputeEngineCredentials.java b/oauth2_http/java/com/google/auth/oauth2/ComputeEngineCredentials.java
index 2e0c321d1..4fd1c1014 100644
--- a/oauth2_http/java/com/google/auth/oauth2/ComputeEngineCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/ComputeEngineCredentials.java
@@ -535,6 +535,7 @@ private void readObject(ObjectInputStream input) throws IOException, ClassNotFou
     transportFactory = newInstance(transportFactoryClassName);
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -675,6 +676,7 @@ public Collection<String> getDefaultScopes() {
       return defaultScopes;
     }
 
+    @Override
     public ComputeEngineCredentials build() {
       return new ComputeEngineCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/DownscopedCredentials.java b/oauth2_http/java/com/google/auth/oauth2/DownscopedCredentials.java
index a8447a69a..43709d779 100644
--- a/oauth2_http/java/com/google/auth/oauth2/DownscopedCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/DownscopedCredentials.java
@@ -185,6 +185,7 @@ public Builder setHttpTransportFactory(HttpTransportFactory transportFactory) {
       return this;
     }
 
+    @Override
     public DownscopedCredentials build() {
       return new DownscopedCredentials(
           sourceCredential, credentialAccessBoundary, transportFactory);
diff --git a/oauth2_http/java/com/google/auth/oauth2/ExternalAccountAuthorizedUserCredentials.java b/oauth2_http/java/com/google/auth/oauth2/ExternalAccountAuthorizedUserCredentials.java
index e713f7452..d01623a62 100644
--- a/oauth2_http/java/com/google/auth/oauth2/ExternalAccountAuthorizedUserCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/ExternalAccountAuthorizedUserCredentials.java
@@ -294,6 +294,7 @@ public boolean equals(Object obj) {
         && Objects.equals(this.quotaProjectId, credentials.quotaProjectId);
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -501,6 +502,7 @@ public Builder setClientSecret(String clientSecret) {
      * @param quotaProjectId the quota and billing project id to set
      * @return this {@code Builder} object
      */
+    @Override
     @CanIgnoreReturnValue
     public Builder setQuotaProjectId(String quotaProjectId) {
       super.setQuotaProjectId(quotaProjectId);
@@ -513,12 +515,14 @@ public Builder setQuotaProjectId(String quotaProjectId) {
      * @param accessToken the access token
      * @return this {@code Builder} object
      */
+    @Override
     @CanIgnoreReturnValue
     public Builder setAccessToken(AccessToken accessToken) {
       super.setAccessToken(accessToken);
       return this;
     }
 
+    @Override
     public ExternalAccountAuthorizedUserCredentials build() {
       return new ExternalAccountAuthorizedUserCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java b/oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java
index bccd943eb..804df70df 100644
--- a/oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java
@@ -848,6 +848,7 @@ public Builder setTokenInfoUrl(String tokenInfoUrl) {
      * @param quotaProjectId the quota and billing project id to set
      * @return this {@code Builder} object
      */
+    @Override
     @CanIgnoreReturnValue
     public Builder setQuotaProjectId(String quotaProjectId) {
       super.setQuotaProjectId(quotaProjectId);
@@ -941,6 +942,7 @@ Builder setEnvironmentProvider(EnvironmentProvider environmentProvider) {
       return this;
     }
 
+    @Override
     public abstract ExternalAccountCredentials build();
   }
 }
diff --git a/oauth2_http/java/com/google/auth/oauth2/GdchCredentials.java b/oauth2_http/java/com/google/auth/oauth2/GdchCredentials.java
index 4ffa87520..642dd7858 100644
--- a/oauth2_http/java/com/google/auth/oauth2/GdchCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/GdchCredentials.java
@@ -311,6 +311,7 @@ public static Builder newBuilder() {
     return new Builder();
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -475,6 +476,7 @@ public int getLifetime() {
       return lifetime;
     }
 
+    @Override
     public GdchCredentials build() {
       return new GdchCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java b/oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java
index 4c10008c7..41388a9e8 100644
--- a/oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java
@@ -406,6 +406,7 @@ public static Builder newBuilder() {
     return new Builder();
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -502,6 +503,7 @@ protected Builder(GoogleCredentials.Builder builder) {
       this.universeDomain = builder.universeDomain;
     }
 
+    @Override
     public GoogleCredentials build() {
       return new GoogleCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/IdTokenCredentials.java b/oauth2_http/java/com/google/auth/oauth2/IdTokenCredentials.java
index a9bd03208..42bdbaa6e 100644
--- a/oauth2_http/java/com/google/auth/oauth2/IdTokenCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/IdTokenCredentials.java
@@ -149,6 +149,7 @@ public boolean equals(Object obj) {
         && Objects.equals(this.targetAudience, other.targetAudience);
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder()
         .setIdTokenProvider(this.idTokenProvider)
@@ -198,6 +199,7 @@ public List<IdTokenProvider.Option> getOptions() {
       return this.options;
     }
 
+    @Override
     public IdTokenCredentials build() {
       return new IdTokenCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/IdentityPoolCredentials.java b/oauth2_http/java/com/google/auth/oauth2/IdentityPoolCredentials.java
index fcfc7bb9b..776a01e05 100644
--- a/oauth2_http/java/com/google/auth/oauth2/IdentityPoolCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/IdentityPoolCredentials.java
@@ -183,6 +183,7 @@ public static class Builder extends ExternalAccountCredentials.Builder {
       super(credentials);
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setWorkforcePoolUserProject(String workforcePoolUserProject) {
       super.setWorkforcePoolUserProject(workforcePoolUserProject);
diff --git a/oauth2_http/java/com/google/auth/oauth2/ImpersonatedCredentials.java b/oauth2_http/java/com/google/auth/oauth2/ImpersonatedCredentials.java
index 641ddc462..f66b29a96 100644
--- a/oauth2_http/java/com/google/auth/oauth2/ImpersonatedCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/ImpersonatedCredentials.java
@@ -602,6 +602,7 @@ public boolean equals(Object obj) {
         && Objects.equals(this.iamEndpointOverride, other.iamEndpointOverride);
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this.sourceCredentials, this.targetPrincipal);
   }
@@ -688,6 +689,7 @@ public HttpTransportFactory getHttpTransportFactory() {
       return transportFactory;
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setQuotaProjectId(String quotaProjectId) {
       super.setQuotaProjectId(quotaProjectId);
@@ -710,6 +712,7 @@ public Calendar getCalendar() {
       return this.calendar;
     }
 
+    @Override
     public ImpersonatedCredentials build() {
       return new ImpersonatedCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java b/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java
index d1332bb29..94ddeb549 100644
--- a/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java
@@ -630,6 +630,7 @@ public ListenableFutureTask<OAuthValue> getTask() {
       return this.task;
     }
 
+    @Override
     public void run() {
       task.run();
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/OAuth2CredentialsWithRefresh.java b/oauth2_http/java/com/google/auth/oauth2/OAuth2CredentialsWithRefresh.java
index 14e3ddae8..954378f7b 100644
--- a/oauth2_http/java/com/google/auth/oauth2/OAuth2CredentialsWithRefresh.java
+++ b/oauth2_http/java/com/google/auth/oauth2/OAuth2CredentialsWithRefresh.java
@@ -113,6 +113,7 @@ public Builder setRefreshHandler(OAuth2RefreshHandler handler) {
       return this;
     }
 
+    @Override
     public OAuth2CredentialsWithRefresh build() {
       return new OAuth2CredentialsWithRefresh(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/OAuth2Utils.java b/oauth2_http/java/com/google/auth/oauth2/OAuth2Utils.java
index a1d276bad..d4a29d515 100644
--- a/oauth2_http/java/com/google/auth/oauth2/OAuth2Utils.java
+++ b/oauth2_http/java/com/google/auth/oauth2/OAuth2Utils.java
@@ -99,6 +99,7 @@ class OAuth2Utils {
 
   static class DefaultHttpTransportFactory implements HttpTransportFactory {
 
+    @Override
     public HttpTransport create() {
       return HTTP_TRANSPORT;
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/ServiceAccountCredentials.java b/oauth2_http/java/com/google/auth/oauth2/ServiceAccountCredentials.java
index 69361e00c..a133b2e5b 100644
--- a/oauth2_http/java/com/google/auth/oauth2/ServiceAccountCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/ServiceAccountCredentials.java
@@ -996,6 +996,7 @@ public static Builder newBuilder() {
     return new Builder();
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -1103,6 +1104,7 @@ public Builder setHttpTransportFactory(HttpTransportFactory transportFactory) {
       return this;
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setQuotaProjectId(String quotaProjectId) {
       super.setQuotaProjectId(quotaProjectId);
@@ -1188,6 +1190,7 @@ public boolean isDefaultRetriesEnabled() {
       return defaultRetriesEnabled;
     }
 
+    @Override
     public ServiceAccountCredentials build() {
       return new ServiceAccountCredentials(this);
     }
diff --git a/oauth2_http/java/com/google/auth/oauth2/UserCredentials.java b/oauth2_http/java/com/google/auth/oauth2/UserCredentials.java
index d4358d93b..67859c33d 100644
--- a/oauth2_http/java/com/google/auth/oauth2/UserCredentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/UserCredentials.java
@@ -372,6 +372,7 @@ public static Builder newBuilder() {
     return new Builder();
   }
 
+  @Override
   public Builder toBuilder() {
     return new Builder(this);
   }
@@ -425,24 +426,28 @@ public Builder setHttpTransportFactory(HttpTransportFactory transportFactory) {
       return this;
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setAccessToken(AccessToken token) {
       super.setAccessToken(token);
       return this;
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setExpirationMargin(Duration expirationMargin) {
       super.setExpirationMargin(expirationMargin);
       return this;
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setRefreshMargin(Duration refreshMargin) {
       super.setRefreshMargin(refreshMargin);
       return this;
     }
 
+    @Override
     @CanIgnoreReturnValue
     public Builder setQuotaProjectId(String quotaProjectId) {
       super.setQuotaProjectId(quotaProjectId);
@@ -469,6 +474,7 @@ public HttpTransportFactory getHttpTransportFactory() {
       return transportFactory;
     }
 
+    @Override
     public UserCredentials build() {
       return new UserCredentials(this);
     }
diff --git a/oauth2_http/javatests/com/google/auth/oauth2/DefaultCredentialsProviderTest.java b/oauth2_http/javatests/com/google/auth/oauth2/DefaultCredentialsProviderTest.java
index 0047cd988..1bb44520e 100644
--- a/oauth2_http/javatests/com/google/auth/oauth2/DefaultCredentialsProviderTest.java
+++ b/oauth2_http/javatests/com/google/auth/oauth2/DefaultCredentialsProviderTest.java
@@ -606,6 +606,7 @@ private String tempFilePath(String filename) {
   private class LogHandler extends Handler {
     LogRecord lastRecord;
 
+    @Override
     public void publish(LogRecord record) {
       lastRecord = record;
     }
@@ -614,8 +615,10 @@ public LogRecord getRecord() {
       return lastRecord;
     }
 
+    @Override
     public void close() {}
 
+    @Override
     public void flush() {}
   }
 
diff --git a/oauth2_http/pom.xml b/oauth2_http/pom.xml
index a1af91846..dc4441677 100644
--- a/oauth2_http/pom.xml
+++ b/oauth2_http/pom.xml
@@ -161,6 +161,14 @@
             <include>**/functional/*.java</include>
           </includes>
         </configuration>
+        <executions>
+          <execution>
+            <goals>
+              <goal>integration-test</goal>
+              <goal>verify</goal>
+            </goals>
+          </execution>
+        </executions>
       </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
@@ -175,18 +183,6 @@
           <reportNameSuffix>sponge_log</reportNameSuffix>
         </configuration>
       </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-failsafe-plugin</artifactId>
-        <executions>
-          <execution>
-            <goals>
-              <goal>integration-test</goal>
-              <goal>verify</goal>
-            </goals>
-          </execution>
-        </executions>
-      </plugin>
     </plugins>
   </build>
 
@@ -231,12 +227,6 @@
       <version>1.3</version>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>junit</groupId>
-      <artifactId>junit</artifactId>
-      <version>4.13.2</version>
-      <scope>test</scope>
-    </dependency>
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>