Added missing test

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/client/TraceExchangeFilterFunctionHttpAdapterTests.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2013-2019 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.springframework.cloud.sleuth.instrument.web.client;
+
+import org.assertj.core.api.BDDAssertions;
+import org.junit.Test;
+import org.mockito.BDDMockito;
+
+import org.springframework.web.reactive.function.client.ClientResponse;
+
+public class TraceExchangeFilterFunctionHttpAdapterTests {
+
+	@Test
+	public void should_return_0_when_invalid_status_code_is_returned() {
+		ClientResponse clientResponse = BDDMockito.mock(ClientResponse.class);
+		BDDMockito.given(clientResponse.rawStatusCode())
+				.willThrow(new IllegalStateException("Boom"));
+		TraceExchangeFilterFunction.HttpClientResponse response = new TraceExchangeFilterFunction.HttpClientResponse(
+				clientResponse);
+
+		Integer statusCode = response.statusCode();
+
+		BDDAssertions.then(statusCode).isZero();
+	}
+
+	@Test
+	public void should_return_status_code_when_valid_status_code_is_returned() {
+		ClientResponse clientResponse = BDDMockito.mock(ClientResponse.class);
+		BDDMockito.given(clientResponse.rawStatusCode()).willReturn(200);
+		TraceExchangeFilterFunction.HttpClientResponse response = new TraceExchangeFilterFunction.HttpClientResponse(
+				clientResponse);
+
+		Integer statusCode = response.statusCode();
+
+		BDDAssertions.then(statusCode).isEqualTo(200);
+	}
+
+}