diff --git a/src/main/java/learnrxjava/ComposableListSolutions.java b/src/main/java/learnrxjava/ComposableListSolutions.java
index 5df5b0b..c2256d2 100644
--- a/src/main/java/learnrxjava/ComposableListSolutions.java
+++ b/src/main/java/learnrxjava/ComposableListSolutions.java
@@ -793,7 +793,7 @@ public static ComposableList<JSON> exercise19() {
                     return v.boxarts.reduce((max, box) -> {
                         int maxSize = max.height * max.width;
                         int boxSize = box.height * box.width;
-                        if(boxSize > maxSize) {
+                        if(boxSize < maxSize) {
                             return box;
                         } else {
                             return max;
diff --git a/src/main/java/learnrxjava/ObservableExercises.java b/src/main/java/learnrxjava/ObservableExercises.java
index 9f7f408..a7c5d00 100644
--- a/src/main/java/learnrxjava/ObservableExercises.java
+++ b/src/main/java/learnrxjava/ObservableExercises.java
@@ -7,7 +7,7 @@
 public class ObservableExercises {
 
     /**
-     * Return an Observable that emits a single value "Hello World"
+     * Return an Observable that emits a single value "Hello World!"
      * 
      * @return "Hello World!"
      */
@@ -72,7 +72,7 @@ public Observable<Integer> exerciseReduce(Observable<Integer> nums) {
     }
 
     /**
-     * Retrieve the id, title, and smallest box art url for every video.
+     * Retrieve the id, title, and <b>smallest</b> box art url for every video.
      * 
      * Now let's try combining reduce() with our other functions to build more complex queries.
      * 
diff --git a/src/main/java/learnrxjava/ObservableSolutions.java b/src/main/java/learnrxjava/ObservableSolutions.java
index 908ea57..405682a 100644
--- a/src/main/java/learnrxjava/ObservableSolutions.java
+++ b/src/main/java/learnrxjava/ObservableSolutions.java
@@ -98,7 +98,7 @@ public Observable<JSON> exerciseMovie(Observable<Movies> movies) {
                 return v.boxarts.reduce((max, box) -> {
                     int maxSize = max.height * max.width;
                     int boxSize = box.height * box.width;
-                    if (boxSize > maxSize) {
+                    if (boxSize < maxSize) {
                         return box;
                     } else {
                         return max;
diff --git a/src/main/java/learnrxjava/examples/ScanVsReduceExample.java b/src/main/java/learnrxjava/examples/ScanVsReduceExample.java
index 35afce5..2c2ec65 100644
--- a/src/main/java/learnrxjava/examples/ScanVsReduceExample.java
+++ b/src/main/java/learnrxjava/examples/ScanVsReduceExample.java
@@ -7,14 +7,14 @@
 public class ScanVsReduceExample {
 
     public static void main(String... args) {
-        Observable.range(0, 10).reduce(() -> new ArrayList<Integer>(), (list, i) -> {
+        Observable.range(0, 10).reduce(new ArrayList<>(), (list, i) -> {
             list.add(i);
             return list;
         }).forEach(System.out::println);
 
         System.out.println("... vs ...");
 
-        Observable.range(0, 10).scan(() -> new ArrayList<Integer>(), (list, i) -> {
+        Observable.range(0, 10).scan(new ArrayList<>(), (list, i) -> {
             list.add(i);
             return list;
         }).forEach(System.out::println);
diff --git a/src/main/java/learnrxjava/examples/UnitTesting.java b/src/main/java/learnrxjava/examples/UnitTesting.java
index 398d4b2..c8f3221 100644
--- a/src/main/java/learnrxjava/examples/UnitTesting.java
+++ b/src/main/java/learnrxjava/examples/UnitTesting.java
@@ -1,5 +1,29 @@
 package learnrxjava.examples;
 
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+
+import rx.Observable;
+import rx.observers.TestSubscriber;
+import rx.schedulers.Schedulers;
+import rx.schedulers.TestScheduler;
+
 public class UnitTesting {
 
+    public static void main(String... args) {
+        TestScheduler test = Schedulers.test();
+        TestSubscriber<String> ts = new TestSubscriber<>();
+
+        Observable.interval(200, TimeUnit.MILLISECONDS, test)
+                .map(i -> {
+                    return i + " value";
+                }).subscribe(ts);
+
+        test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
+        ts.assertReceivedOnNext(Arrays.asList("0 value"));
+
+        test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
+        ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value", "2 value", "3 value", "4 value"));
+    }
+
 }
diff --git a/src/test/java/learnrxjava/ObservableSolutionsTest.java b/src/test/java/learnrxjava/ObservableSolutionsTest.java
index d75ac96..a7e2fa7 100644
--- a/src/test/java/learnrxjava/ObservableSolutionsTest.java
+++ b/src/test/java/learnrxjava/ObservableSolutionsTest.java
@@ -168,13 +168,13 @@ public void exerciseMovie() {
         Map<Integer, JSON> map = getImpl().exerciseMovie(movies).toMap(i -> (int) i.get("id")).toBlocking().single();
         System.out.println(map);
         assertTrue(map.containsKey(70111470));
-        assertEquals(map.get(70111470).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/DieHard200.jpg, id=70111470, title=Die Hard}");
+        assertEquals(map.get(70111470).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/DieHard150.jpg, id=70111470, title=Die Hard}");
         assertTrue(map.containsKey(654356453));
-        assertEquals(map.get(654356453).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/BadBoys200.jpg, id=654356453, title=Bad Boys}");
+        assertEquals(map.get(654356453).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/BadBoys140.jpg, id=654356453, title=Bad Boys}");
         assertTrue(map.containsKey(65432445));
-        assertEquals(map.get(65432445).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/TheChamber200.jpg, id=65432445, title=The Chamber}");
+        assertEquals(map.get(65432445).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/TheChamber130.jpg, id=65432445, title=The Chamber}");
         assertTrue(map.containsKey(675465));
-        assertEquals(map.get(675465).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/Fracture300.jpg, id=675465, title=Fracture}");
+        assertEquals(map.get(675465).toString(), "{boxart=http://cdn-0.nflximg.com/images/2891/Fracture120.jpg, id=675465, title=Fracture}");
     }
 
     @Test