Implement per_rpc_creds test

interop-testing/src/main/java/io/grpc/testing/integration/AbstractTransportTest.java

@@ -593,9 +593,9 @@ public abstract class AbstractTransportTest {
         requestHeadersCapture.get().get(GrpcUtil.TIMEOUT_KEY));
     Assert.assertTrue(
         "configuredTimeoutMinutes=" + configuredTimeoutMinutes
-        + ", transferredTimeoutMinutes=" + transferredTimeoutMinutes,
+            + ", transferredTimeoutMinutes=" + transferredTimeoutMinutes,
         configuredTimeoutMinutes - transferredTimeoutMinutes >= 0
-        && configuredTimeoutMinutes - transferredTimeoutMinutes <= 1);
+            && configuredTimeoutMinutes - transferredTimeoutMinutes <= 1);
   }
 
   @Test
@@ -847,6 +847,15 @@ public abstract class AbstractTransportTest {
         authScope.contains(response.getOauthScope()));
   }
 
+  /** Sends a unary rpc with "per rpc" raw oauth2 access token credentials. */
+  public void perRpcCreds(String jsonKey, InputStream credentialsStream, String oauthScope)
+      throws Exception {
+    // In gRpc Java, we don't have per Rpc credentials, user can use an intercepted stub only once
+    // for that purpose.
+    // So, this test is identical to oauth2_auth_token test.
+    oauth2AuthToken(jsonKey, credentialsStream, oauthScope);
+  }
+
   protected static void assertSuccess(StreamRecorder<?> recorder) {
     if (recorder.getError() != null) {
       throw new AssertionError(recorder.getError());

interop-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java

@@ -168,6 +168,7 @@ public class TestServiceClient {
           + "\n      service_account_creds: large_unary with service_account auth"
           + "\n      compute_engine_creds: large_unary with compute engine auth"
           + "\n      oauth2_auth_token: raw oauth2 access token auth"
+          + "\n      per_rpc_creds: per rpc raw oauth2 access token auth"
           + "\n      cancel_after_begin: cancel stream after starting it"
           + "\n      cancel_after_first_response: cancel on first response"
           + "\n  --use_tls=true|false        Whether to use TLS. Default " + c.useTls
@@ -233,6 +234,10 @@ public class TestServiceClient {
       String jsonKey = Files.toString(new File(serviceAccountKeyFile), Charset.forName("UTF-8"));
       FileInputStream credentialsStream = new FileInputStream(new File(serviceAccountKeyFile));
       tester.oauth2AuthToken(jsonKey, credentialsStream, oauthScope);
+    } else if ("per_rpc_creds".equals(testCase)) {
+      String jsonKey = Files.toString(new File(serviceAccountKeyFile), Charset.forName("UTF-8"));
+      FileInputStream credentialsStream = new FileInputStream(new File(serviceAccountKeyFile));
+      tester.perRpcCreds(jsonKey, credentialsStream, oauthScope);
     } else if ("cancel_after_begin".equals(testCase)) {
       tester.cancelAfterBegin();
     } else if ("cancel_after_first_response".equals(testCase)) {