Added support for fixed and random delays in the DSL

src/main/java/org/wiremock/grpc/dsl/GrpcResponseDefinitionBuilder.java

@@ -16,7 +16,7 @@
 package org.wiremock.grpc.dsl;
 
 import com.github.tomakehurst.wiremock.client.ResponseDefinitionBuilder;
-import com.github.tomakehurst.wiremock.http.Fault;
+import com.github.tomakehurst.wiremock.http.*;
 import org.wiremock.annotations.Beta;
 
 @Beta(justification = "Incubating extension: https://github.com/wiremock/wiremock/issues/2383")
@@ -33,6 +33,8 @@ public class GrpcResponseDefinitionBuilder {
 
   private boolean templatingEnabled;
 
+  private DelayDistribution delay;
+
   public GrpcResponseDefinitionBuilder(WireMockGrpc.Status grpcStatus) {
     this(grpcStatus, null);
   }
@@ -59,6 +61,26 @@ public GrpcResponseDefinitionBuilder withTemplatingEnabled(boolean enabled) {
     return this;
   }
 
+  public GrpcResponseDefinitionBuilder withFixedDelay(long milliseconds) {
+    this.delay = new FixedDelayDistribution(milliseconds);
+    return null;
+  }
+
+  public GrpcResponseDefinitionBuilder withRandomDelay(DelayDistribution distribution) {
+    this.delay = distribution;
+    return this;
+  }
+
+  public GrpcResponseDefinitionBuilder withLogNormalRandomDelay(
+      double medianMilliseconds, double sigma) {
+    return withRandomDelay(new LogNormal(medianMilliseconds, sigma));
+  }
+
+  public GrpcResponseDefinitionBuilder withUniformRandomDelay(
+      int lowerMilliseconds, int upperMilliseconds) {
+    return withRandomDelay(new UniformDistribution(lowerMilliseconds, upperMilliseconds));
+  }
+
   public ResponseDefinitionBuilder build() {
     if (fault != null) {
       return ResponseDefinitionBuilder.responseDefinition().withFault(fault);
@@ -76,6 +98,10 @@ public ResponseDefinitionBuilder build() {
       responseDefinitionBuilder.withTransformers("response-template");
     }
 
+    if (delay != null) {
+      responseDefinitionBuilder.withRandomDelay(delay);
+    }
+
     return responseDefinitionBuilder.withBody(json);
   }
 }

src/main/java/org/wiremock/grpc/dsl/GrpcStubMappingBuilder.java

@@ -19,7 +19,10 @@
 
 import com.github.tomakehurst.wiremock.client.MappingBuilder;
 import com.github.tomakehurst.wiremock.client.WireMock;
+import com.github.tomakehurst.wiremock.http.DelayDistribution;
 import com.github.tomakehurst.wiremock.http.Fault;
+import com.github.tomakehurst.wiremock.http.LogNormal;
+import com.github.tomakehurst.wiremock.http.UniformDistribution;
 import com.github.tomakehurst.wiremock.matching.StringValuePattern;
 import com.github.tomakehurst.wiremock.stubbing.StubMapping;
 import java.util.ArrayList;
@@ -58,6 +61,25 @@ public GrpcStubMappingBuilder willReturn(Fault fault) {
     return this;
   }
 
+  public GrpcStubMappingBuilder withFixedDelay(long milliseconds) {
+    responseBuilder.withFixedDelay(milliseconds);
+    return this;
+  }
+
+  public GrpcStubMappingBuilder withDelay(DelayDistribution delay) {
+    responseBuilder.withRandomDelay(delay);
+    return this;
+  }
+
+  public GrpcStubMappingBuilder withLogNormalRandomDelay(double medianMilliseconds, double sigma) {
+    return withDelay(new LogNormal(medianMilliseconds, sigma));
+  }
+
+  public GrpcStubMappingBuilder withUniformRandomDelay(
+      int lowerMilliseconds, int upperMilliseconds) {
+    return withDelay(new UniformDistribution(lowerMilliseconds, upperMilliseconds));
+  }
+
   public StubMapping build(String serviceName) {
     final MappingBuilder mappingBuilder = WireMock.post(grpcUrlPath(serviceName, method));
     requestMessageJsonPatterns.forEach(mappingBuilder::withRequestBody);

src/main/java/org/wiremock/grpc/internal/Delays.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2023 Thomas Akehurst
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.wiremock.grpc.internal;
+
+import com.github.tomakehurst.wiremock.http.Response;
+import java.util.concurrent.TimeUnit;
+
+public class Delays {
+
+  public static void delayIfRequired(Response response) {
+    final long delayMillis = response.getInitialDelay();
+    if (delayMillis > 0) {
+      try {
+        TimeUnit.MILLISECONDS.sleep(delayMillis);
+      } catch (InterruptedException var4) {
+        Thread.currentThread().interrupt();
+      }
+    }
+  }
+}

src/main/java/org/wiremock/grpc/internal/UnaryServerCallHandler.java

@@ -17,6 +17,7 @@
 
 import static org.wiremock.grpc.dsl.GrpcResponseDefinitionBuilder.GRPC_STATUS_NAME;
 import static org.wiremock.grpc.dsl.GrpcResponseDefinitionBuilder.GRPC_STATUS_REASON;
+import static org.wiremock.grpc.internal.Delays.delayIfRequired;
 
 import com.github.tomakehurst.wiremock.http.HttpHeader;
 import com.github.tomakehurst.wiremock.http.StubRequestHandler;
@@ -62,6 +63,8 @@ public void invoke(DynamicMessage request, StreamObserver<DynamicMessage> respon
         (req, resp, attributes) -> {
           final HttpHeader statusHeader = resp.getHeaders().getHeader(GRPC_STATUS_NAME);
 
+          delayIfRequired(resp);
+
           if (!statusHeader.isPresent() && resp.getStatus() == 404) {
             responseObserver.onError(
                 Status.NOT_FOUND

src/test/java/org/wiremock/grpc/GrpcAcceptanceTest.java

@@ -17,6 +17,7 @@
 
 import static com.github.tomakehurst.wiremock.client.WireMock.*;
 import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.wireMockConfig;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -28,6 +29,7 @@
 import com.github.tomakehurst.wiremock.client.WireMock;
 import com.github.tomakehurst.wiremock.http.Fault;
 import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
+import com.google.common.base.Stopwatch;
 import com.google.protobuf.Empty;
 import io.grpc.ManagedChannel;
 import io.grpc.ManagedChannelBuilder;
@@ -254,4 +256,34 @@ void networkFault() {
         assertThrows(StatusRuntimeException.class, () -> greetingsClient.greet("Alan"));
     assertThat(exception.getMessage(), is("UNKNOWN"));
   }
+
+  @Test
+  void fixedDelay() {
+    mockGreetingService.stubFor(
+        method("greeting")
+            .willReturn(json("{ \"greeting\": \"Delayed hello\" }"))
+            .withFixedDelay(1000));
+
+    Stopwatch stopwatch = Stopwatch.createStarted();
+    String greeting = greetingsClient.greet("Tom");
+    stopwatch.stop();
+
+    assertThat(greeting, is("Delayed hello"));
+    assertThat(stopwatch.elapsed(MILLISECONDS), greaterThanOrEqualTo(1000L));
+  }
+
+  @Test
+  void randomDelay() {
+    mockGreetingService.stubFor(
+        method("greeting")
+            .willReturn(json("{ \"greeting\": \"Delayed hello\" }"))
+            .withUniformRandomDelay(500, 1000));
+
+    Stopwatch stopwatch = Stopwatch.createStarted();
+    String greeting = greetingsClient.greet("Tom");
+    stopwatch.stop();
+
+    assertThat(greeting, is("Delayed hello"));
+    assertThat(stopwatch.elapsed(MILLISECONDS), greaterThanOrEqualTo(500L));
+  }
 }