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testland/grpc-mock

Use when gRPC client code needs tests against a controllable fake server, or a gRPC interceptor needs tests: Go bufconn and mockgen, Python pytest-grpc, JVM in-process servers, Node fake servers, with success, error and timeout responses. Streaming sequences are grpc-streaming-test-author.

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80%

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Java interceptor tests

Java interceptors are objects; call interceptCall directly with stubbed ServerCall / Channel collaborators (Mockito) and assert on captured Status and Metadata.

ServerInterceptor - auth rejection

ServerInterceptor.interceptCall signature per grpc-java javadoc:

<ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
    ServerCall<ReqT, RespT> call,
    Metadata headers,
    ServerCallHandler<ReqT, RespT> next)

Test with a ServerCall stub that captures the close() call:

import io.grpc.*;
import org.junit.Test;
import static org.junit.Assert.*;
import static org.mockito.Mockito.*;

public class AuthInterceptorTest {

    private final ServerInterceptor interceptor = new AuthInterceptor();

    @SuppressWarnings("unchecked")
    @Test
    public void missingAuthHeader_closesWithUnauthenticated() {
        ServerCall<Object, Object> call = mock(ServerCall.class);
        Metadata headers = new Metadata(); // no authorization key
        ServerCallHandler<Object, Object> next = mock(ServerCallHandler.class);

        interceptor.interceptCall(call, headers, next);

        verify(call).close(
            argThat(s -> s.getCode() == Status.Code.UNAUTHENTICATED),
            any(Metadata.class));
        verifyNoInteractions(next);
    }
}

Registration per grpc-java javadoc ServerInterceptors.intercept

note intercept() applies interceptors in reverse order (last interceptor's interceptCall fires first); use interceptForward() to preserve declaration order:

// Last-listed interceptor fires first:
ServerServiceDefinition def =
    ServerInterceptors.intercept(serviceImpl, authInterceptor, loggingInterceptor);

// First-listed interceptor fires first:
ServerServiceDefinition def =
    ServerInterceptors.interceptForward(serviceImpl, authInterceptor, loggingInterceptor);

ClientInterceptor - outbound token injection

ClientInterceptor.interceptCall signature per grpc-java javadoc:

<ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
    MethodDescriptor<ReqT, RespT> method,
    CallOptions callOptions,
    Channel next)

Test that the interceptor attaches the authorization key to outbound headers by capturing Metadata passed to ClientCall.start():

@Test
public void tokenInjector_attachesAuthorizationHeader() {
    ClientInterceptor interceptor = new TokenInjectorInterceptor("Bearer tok");
    Channel channel = mock(Channel.class);
    ClientCall<Object, Object> innerCall = mock(ClientCall.class);
    when(channel.newCall(any(), any())).thenReturn(innerCall);

    ClientCall<Object, Object> call =
        interceptor.interceptCall(methodDescriptor(), CallOptions.DEFAULT, channel);

    Metadata headers = new Metadata();
    call.start(mock(ClientCall.Listener.class), headers);

    String auth = headers.get(Metadata.Key.of("authorization", Metadata.ASCII_STRING_MARSHALLER));
    assertEquals("Bearer tok", auth);
}