Minor review comments

Author: zsmoore

src/main/java/org/dataloader/strategy/BreadthFirstChainedDispatchStrategy.java

@@ -2,6 +2,7 @@
 
 import org.dataloader.DataLoaderRegistry;
 import org.dataloader.DispatchStrategy;
+import org.dataloader.impl.Assertions;
 import org.jspecify.annotations.Nullable;
 
 import java.time.Duration;
@@ -115,11 +116,11 @@ public static class Builder {
         private final ScheduledExecutorService scheduledExecutorService;
 
         public Builder(ScheduledExecutorService scheduledExecutorService) {
-            this.scheduledExecutorService = scheduledExecutorService;
+            this.scheduledExecutorService = Assertions.nonNull(scheduledExecutorService);
         }
 
         public Builder setFallbackTimeout(Duration fallbackTimeout) {
-            this.fallbackTimeout = fallbackTimeout;
+            this.fallbackTimeout = Assertions.nonNull(fallbackTimeout);
             return this;
         }
 

src/test/java/org/dataloader/strategy/BreadthFirstChainedDispatchStrategyTest.java

@@ -31,7 +31,7 @@ public void setUp() {
 
     @AfterEach
     public void cleanUp() {
-        this.scheduledExecutorService.shutdown();
+        this.scheduledExecutorService.shutdownNow();
     }
 
     @Test