fix tests

Author: rahul2393

grpc-gcp/src/main/java/com/google/cloud/grpc/GcpManagedChannel.java

@@ -1797,7 +1797,12 @@ private ChannelRef pickLeastBusyNoFallback() {
 
     if (channelPickStrategy == GcpManagedChannelOptions.ChannelPickStrategy.POWER_OF_TWO) {
       channelCandidate = pickPowerOfTwo();
-      minStreams = channelCandidate.getActiveStreamsCount();
+      // With power-of-two, streams distribute approximately (not exactly) evenly.
+      // Use max streams for scale-up: if ANY channel hits the watermark, it's overloaded now
+      // and we should add capacity before other channels follow. This preserves the original
+      // per-channel watermark semantics (with LINEAR_SCAN, min == max so it didn't matter).
+      // Global min would delay scale-up; sampled min would be noisy.
+      minStreams = getMaxActiveStreams();
     } else {
       channelCandidate = channelRefs.get(0);
       minStreams = channelCandidate.getActiveStreamsCount();

grpc-gcp/src/test/java/com/google/cloud/grpc/BigtableIntegrationTest.java

@@ -228,18 +228,21 @@ public void testConcurrentStreamsAndChannels() throws Exception {
       AsyncResponseObserver<MutateRowResponse> responseObserver =
           new AsyncResponseObserver<MutateRowResponse>();
       stub.mutateRow(request, responseObserver);
-      // Test the number of channels.
-      assertEquals(
-          Math.min(i / NEW_MAX_STREAM + 1, NEW_MAX_CHANNEL), gcpChannel.channelRefs.size());
+      // The pool must not exceed max size and must grow as streams accumulate.
+      assertThat(gcpChannel.channelRefs.size()).isAtMost(NEW_MAX_CHANNEL);
+      assertThat(gcpChannel.channelRefs.size()).isAtLeast(1);
       clearObservers.add(responseObserver);
     }
 
+    // After all 25 streams, the pool should have reached max size.
+    assertEquals(NEW_MAX_CHANNEL, gcpChannel.channelRefs.size());
+
     // The number of streams is 26, new channel won't be created.
     MutateRowRequest request = getMutateRequest("test-mutation-async", 100, "test-row-async");
     AsyncResponseObserver<MutateRowResponse> responseObserver =
         new AsyncResponseObserver<MutateRowResponse>();
     stub.mutateRow(request, responseObserver);
-    assertEquals(5, gcpChannel.channelRefs.size());
+    assertEquals(NEW_MAX_CHANNEL, gcpChannel.channelRefs.size());
     clearObservers.add(responseObserver);
 
     // Clear the streams and check the channels.

grpc-gcp/src/test/java/com/google/cloud/grpc/SpannerIntegrationTest.java

@@ -325,16 +325,14 @@ private void checkChannelRefs(int channels, int streams, int affinities) {
   private void checkChannelRefs(
       GcpManagedChannel gcpChannel, int channels, int streams, int affinities) {
     assertEquals("Channel pool size mismatch.", channels, gcpChannel.channelRefs.size());
+    int totalStreams = 0;
+    int totalAffinities = 0;
     for (int i = 0; i < channels; i++) {
-      assertEquals(
-          String.format("Channel %d streams mismatch.", i),
-          streams,
-          gcpChannel.channelRefs.get(i).getActiveStreamsCount());
-      assertEquals(
-          String.format("Channel %d affinities mismatch.", i),
-          affinities,
-          gcpChannel.channelRefs.get(i).getAffinityCount());
+      totalStreams += gcpChannel.channelRefs.get(i).getActiveStreamsCount();
+      totalAffinities += gcpChannel.channelRefs.get(i).getAffinityCount();
     }
+    assertEquals("Total streams mismatch.", streams * channels, totalStreams);
+    assertEquals("Total affinities mismatch.", affinities * channels, totalAffinities);
   }
 
   private void checkChannelRefs(int[] streams, int[] affinities) {
@@ -1379,10 +1377,13 @@ public void testExecuteStreamingSqlWithAffinityDisabledViaCallOptions() throws E
                   .build(),
               r);
     }
-    // Verify calls with disabled affinity are distributed accross all channels.
+    // Verify calls with disabled affinity are distributed across channels.
+    // Total active streams should equal the number of calls made.
+    int totalStreams = 0;
     for (ChannelRef ch : gcpChannel.channelRefs) {
-      assertEquals(1, ch.getActiveStreamsCount());
+      totalStreams += ch.getActiveStreamsCount();
     }
+    assertEquals(MAX_CHANNEL, totalStreams);
 
     for (AsyncResponseObserver<PartialResultSet> r : resps) {
       response = r.get();