Fix ext_proc fuzzer test issues. (envoyproxy#27619)

* Fix ext_proc fuzzer test issues.

Signed-off-by: Yanjun Xiang <yanjunxiang@google.com>
Signed-off-by: Ryan Eskin <ryan.eskin89@protonmail.com>

test/extensions/filters/http/ext_proc/unit_test_fuzz/ext_proc_unit_test_fuzz.cc

@@ -18,13 +18,18 @@ namespace UnitTestFuzz {
 
 class FuzzerMocks {
 public:
-  FuzzerMocks() : addr_(std::make_shared<Network::Address::PipeInstance>("/test/test.sock")) {
+  FuzzerMocks()
+      : addr_(std::make_shared<Network::Address::PipeInstance>("/test/test.sock")), buffer_("foo") {
     ON_CALL(decoder_callbacks_, connection())
         .WillByDefault(Return(OptRef<const Network::Connection>{connection_}));
     connection_.stream_info_.downstream_connection_info_provider_->setRemoteAddress(addr_);
     connection_.stream_info_.downstream_connection_info_provider_->setLocalAddress(addr_);
     ON_CALL(decoder_callbacks_, addDecodedTrailers()).WillByDefault(ReturnRef(request_trailers_));
     ON_CALL(encoder_callbacks_, addEncodedTrailers()).WillByDefault(ReturnRef(response_trailers_));
+    ON_CALL(decoder_callbacks_, decodingBuffer()).WillByDefault(Return(&buffer_));
+    ON_CALL(encoder_callbacks_, encodingBuffer()).WillByDefault(Return(&buffer_));
+    ON_CALL(decoder_callbacks_, decoderBufferLimit()).WillByDefault(Return(1024));
+    ON_CALL(encoder_callbacks_, encoderBufferLimit()).WillByDefault(Return(1024));
   }
 
   NiceMock<Http::MockStreamDecoderFilterCallbacks> decoder_callbacks_;
@@ -33,6 +38,7 @@ class FuzzerMocks {
   NiceMock<Envoy::Network::MockConnection> connection_;
   NiceMock<Http::TestRequestTrailerMapImpl> request_trailers_;
   NiceMock<Http::TestResponseTrailerMapImpl> response_trailers_;
+  NiceMock<Buffer::OwnedImpl> buffer_;
   testing::NiceMock<StreamInfo::MockStreamInfo> async_client_stream_info_;
 };
 
@@ -72,8 +78,8 @@ DEFINE_PROTO_FUZZER(
   filter->setDecoderFilterCallbacks(mocks.decoder_callbacks_);
   filter->setEncoderFilterCallbacks(mocks.encoder_callbacks_);
 
-  ON_CALL(*client, start(_, _, _))
-      .WillByDefault(Invoke(
+  EXPECT_CALL(*client, start(_, _, _))
+      .WillRepeatedly(Invoke(
           [&](ExternalProcessing::ExternalProcessorCallbacks&,
               const envoy::config::core::v3::GrpcService&,
               const StreamInfo::StreamInfo&) -> ExternalProcessing::ExternalProcessorStreamPtr {
@@ -88,7 +94,7 @@ DEFINE_PROTO_FUZZER(
                     }));
             EXPECT_CALL(*stream, streamInfo())
                 .WillRepeatedly(ReturnRef(mocks.async_client_stream_info_));
-            ON_CALL(*stream, close()).WillByDefault(Return(false));
+            EXPECT_CALL(*stream, close()).WillRepeatedly(Return(false));
             return stream;
           }));