Fix test failures, pom cross-language group exclusion, and empty tuple seed hash

pom.xml

@@ -146,9 +146,9 @@ under the License.
     <!-- Language Groups -->
     <testng.check_java_cpp>${testng.generate_java_files},${testng.check_java_files},${testng.check_cpp_files}</testng.check_java_cpp>
     <testng.check_go_rust>${testng.check_go_files},${testng.check_rust_files}</testng.check_go_rust>
-    <testng.check_specials>${testng.check_CL_binaries}${testng.check_cpp_historicals}</testng.check_specials>
+    <testng.check_specials>${testng.check_CL_binaries},${testng.check_cpp_historicals}</testng.check_specials>
     <!-- All Languages & types -->
-    <testng.all_groups>${testng.check_java_cpp}${testng.check_go_rust}${testng.check_specials}</testng.all_groups>
+    <testng.all_groups>${testng.check_java_cpp},${testng.check_go_rust},${testng.check_specials}</testng.all_groups>
 
     <test.data.root>${project.basedir}</test.data.root>
     <print>false</print> <!-- diagnostic printing of file names read/written/not-found in UtilityIO; override with -Dprint=true -->
@@ -870,7 +870,7 @@ under the License.
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-surefire-plugin</artifactId>
             <configuration>
-              <groups>${testng.check_CL_binary_files}</groups>
+              <groups>${testng.check_CL_binaries}</groups>
               <excludedGroups combine.self="override"></excludedGroups>
             </configuration>
           </plugin>
@@ -886,7 +886,7 @@ under the License.
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-surefire-plugin</artifactId>
             <configuration>
-              <groups>${testng.check_cpp_historical_files}</groups>
+              <groups>${testng.check_cpp_historicals}</groups>
               <excludedGroups combine.self="override"></excludedGroups>
             </configuration>
           </plugin>

src/main/java/org/apache/datasketches/tdigest/TDigestDouble.java

@@ -117,10 +117,10 @@ public void update(final double value) {
    */
   public void merge(final TDigestDouble other) {
     if (other.isEmpty()) { return; }
+    Math.addExact(getTotalWeight(), other.getTotalWeight());
     // Extreme centroid means are not the true min/max when those centroids have weight > 1.
     minValue_ = Math.min(minValue_, other.minValue_);
     maxValue_ = Math.max(maxValue_, other.maxValue_);
-    Math.addExact(getTotalWeight(), other.getTotalWeight());
     final int num = numCentroids_ + numBuffered_ + other.numCentroids_ + other.numBuffered_;
     final double[] values = new double[num];
     final long[] weights = new long[num];

src/main/java/org/apache/datasketches/tuple/CompactTupleSketch.java

@@ -221,7 +221,7 @@ public byte[] toByteArray() {
       | (1 << Flags.IS_READ_ONLY.ordinal())
       | (isEmpty() ? 1 << Flags.IS_EMPTY.ordinal() : 0)
     );
-    ByteArrayUtil.putShortLE(bytes, offset, defaultSeedHash);
+    ByteArrayUtil.putShortLE(bytes, offset, isEmpty() ? 0 : defaultSeedHash); // empty image carries zero, as in theta
     offset += Short.BYTES;
     if (!isEmpty()) {
       if (!isSingleItem) {

src/test/java/org/apache/datasketches/filters/bloomfilter/BloomFilterTest.java

@@ -295,7 +295,7 @@ public void basicIntersectionTest() {
 
   @Test
   public void basicDifferenceTest() {
-    final long numBits = 8192;
+    final long numBits = 65536; // keeps right's load low (~7.5%) so most left-only items survive
     final int numHashes = 5;
 
     final BloomFilter left = BloomFilterBuilder.createBySize(numBits, numHashes);