test: skip test on emulator (#377)

Skip GapicSpannerRpcTest when an emulator host has been set, as the
test interferes with the check whether the emulator is running.

google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpcTest.java

@@ -20,6 +20,7 @@
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assume.assumeTrue;
 
 import com.google.api.core.ApiFunction;
 import com.google.auth.oauth2.AccessToken;
@@ -71,6 +72,7 @@
 import java.util.regex.Pattern;
 import org.junit.After;
 import org.junit.Before;
+import org.junit.BeforeClass;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -128,6 +130,13 @@ public class GapicSpannerRpcTest {
   private InetSocketAddress address;
   private final Map<SpannerRpc.Option, Object> optionsMap = new HashMap<>();
 
+  @BeforeClass
+  public static void checkNotEmulator() {
+    assumeTrue(
+        "Skip tests when emulator is enabled as this test interferes with the check whether the emulator is running",
+        System.getenv("SPANNER_EMULATOR_HOST") == null);
+  }
+
   @Before
   public void startServer() throws IOException {
     mockSpanner = new MockSpannerServiceImpl();