fix: wait for initialization to finish before test (#161)

The flaky test failure was caused by a lower number of base threads
being calculated before the test started, and not by an unexpected
drop in the number of threads after the test. This is now mitigated by
waiting for the initialization to finish before starting the test.

Fixes #146

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITSpannerOptionsTest.java

@@ -33,8 +33,8 @@
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
-import org.junit.After;
-import org.junit.Before;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
 import org.junit.ClassRule;
 import org.junit.Test;
 import org.junit.experimental.categories.Category;
@@ -47,13 +47,13 @@ public class ITSpannerOptionsTest {
   @ClassRule public static IntegrationTestEnv env = new IntegrationTestEnv();
   private static Database db;
 
-  @Before
-  public void setUp() throws Exception {
+  @BeforeClass
+  public static void setUp() throws Exception {
     db = env.getTestHelper().createTestDatabase();
   }
 
-  @After
-  public void tearDown() throws Exception {
+  @AfterClass
+  public static void tearDown() throws Exception {
     db.drop();
   }
 
@@ -65,9 +65,9 @@ public void tearDown() throws Exception {
 
   @Test
   public void testCloseAllThreadsWhenClosingSpanner() throws InterruptedException {
-    // The IT environment has already started some worker threads.
     int baseThreadCount = getNumberOfThreadsWithName(SPANNER_THREAD_NAME);
     for (int i = 0; i < NUMBER_OF_TEST_RUNS; i++) {
+      waitForStartup();
       assertThat(getNumberOfThreadsWithName(SPANNER_THREAD_NAME)).isAtMost(baseThreadCount);
       // Create Spanner instance.
       // We make a copy of the options instance, as SpannerOptions caches any service object
@@ -136,6 +136,7 @@ public void testCloseAllThreadsWhenClosingSpanner() throws InterruptedException
 
   @Test
   public void testMultipleSpannersFromSameSpannerOptions() throws InterruptedException {
+    waitForStartup();
     int baseThreadCount = getNumberOfThreadsWithName(SPANNER_THREAD_NAME);
     SpannerOptions options = env.getTestHelper().getOptions().toBuilder().build();
     try (Spanner spanner1 = options.getService()) {
@@ -167,6 +168,17 @@ public void testMultipleSpannersFromSameSpannerOptions() throws InterruptedExcep
     assertThat(getNumberOfThreadsWithName(SPANNER_THREAD_NAME)).isAtMost(baseThreadCount);
   }
 
+  private void waitForStartup() throws InterruptedException {
+    // Wait until the IT environment has already started all base worker threads.
+    int threadCount;
+    Stopwatch watch = Stopwatch.createStarted();
+    do {
+      threadCount = getNumberOfThreadsWithName(SPANNER_THREAD_NAME);
+      Thread.sleep(100L);
+    } while (getNumberOfThreadsWithName(SPANNER_THREAD_NAME) > threadCount
+        && watch.elapsed(TimeUnit.SECONDS) < 5);
+  }
+
   private int getNumberOfThreadsWithName(String serviceName) {
     Pattern pattern = Pattern.compile(String.format(THREAD_PATTERN, serviceName));
     ThreadGroup group = Thread.currentThread().getThreadGroup();