diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java
index 225e033..52b792b 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java
@@ -22,6 +22,7 @@
  */
 package com.iluwatar.ambassador;
 
+import com.iluwatar.ambassador.util.RandomProvider;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -31,9 +32,10 @@ import static java.lang.Thread.sleep;
  * A remote legacy application represented by a Singleton implementation.
  */
 public class RemoteService implements RemoteServiceInterface {
-
+  static final int THRESHOLD = 200;
   private static final Logger LOGGER = LoggerFactory.getLogger(RemoteService.class);
   private static RemoteService service = null;
+  private final RandomProvider randomProvider;
 
   static synchronized RemoteService getRemoteService() {
     if (service == null) {
@@ -42,24 +44,33 @@ public class RemoteService implements RemoteServiceInterface {
     return service;
   }
 
-  private RemoteService() {}
+  private RemoteService() {
+    this(Math::random);
+  }
 
   /**
+   * This constuctor is used for testing purposes only.
+   */
+  RemoteService(RandomProvider randomProvider) {
+    this.randomProvider = randomProvider;
+  }
+  /**
    * Remote function takes a value and multiplies it by 10 taking a random amount of time.
    * Will sometimes return -1. This imitates connectivity issues a client might have to account for.
    * @param value integer value to be multiplied.
-   * @return if waitTime is more than 200ms, it returns value * 10, otherwise -1.
+   * @return if waitTime is less than {@link RemoteService#THRESHOLD}, it returns value * 10,
+   *     otherwise {@link RemoteServiceInterface#FAILURE}.
    */
   @Override
   public long doRemoteFunction(int value) {
 
-    long waitTime = (long) Math.floor(Math.random() * 1000);
+    long waitTime = (long) Math.floor(randomProvider.random() * 1000);
 
     try {
       sleep(waitTime);
     } catch (InterruptedException e) {
       LOGGER.error("Thread sleep state interrupted", e);
     }
-    return waitTime >= 200 ? value * 10 : -1;
+    return waitTime <= THRESHOLD ? value * 10 : FAILURE;
   }
 }
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java
index 940313d..e228271 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java
@@ -26,6 +26,7 @@ package com.iluwatar.ambassador;
  * Interface shared by ({@link RemoteService}) and ({@link ServiceAmbassador}).
  */
 interface RemoteServiceInterface {
-    
+  int FAILURE = -1;
+
   long doRemoteFunction(int value) throws Exception;
 }
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java b/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java
index 4be1dfc..52cd7df 100644
--- a/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java
@@ -59,15 +59,15 @@ public class ServiceAmbassador implements RemoteServiceInterface {
   private long safeCall(int value) {
 
     int retries = 0;
-    long result = -1;
+    long result = FAILURE;
 
     for (int i = 0; i < RETRIES; i++) {
 
       if (retries >= RETRIES) {
-        return -1;
+        return FAILURE;
       }
 
-      if ((result = checkLatency(value)) == -1) {
+      if ((result = checkLatency(value)) == FAILURE) {
         LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
         retries++;
         try {
diff --git a/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java b/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java
new file mode 100644
index 0000000..3afa3a6
--- /dev/null
+++ b/ambassador/src/main/java/com/iluwatar/ambassador/util/RandomProvider.java
@@ -0,0 +1,8 @@
+package com.iluwatar.ambassador.util;
+
+/**
+ * An interface for randomness. Useful for testing purposes.
+ */
+public interface RandomProvider {
+  double random();
+}
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java
index 9354c4f..1d69a6a 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java
@@ -24,6 +24,8 @@ package com.iluwatar.ambassador;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 /**
  * Test for {@link Client}
  */
@@ -35,6 +37,6 @@ public class ClientTest {
     Client client = new Client();
     long result = client.useService(10);
 
-    assert result == 100 || result == -1;
+    assertTrue(result == 100 || result == -1);
   }
 }
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java
index e0b297a..7d01469 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java
@@ -22,16 +22,43 @@
  */
 package com.iluwatar.ambassador;
 
+import com.iluwatar.ambassador.util.RandomProvider;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 /**
  * Test for {@link RemoteService}
  */
 public class RemoteServiceTest {
 
   @Test
-  public void test() {
-    long result = RemoteService.getRemoteService().doRemoteFunction(10);
-    assert result == 100 || result == -1;
+  public void testFailedCall() {
+    RemoteService remoteService = new RemoteService(
+        new StaticRandomProvider(0.21));
+    long result = remoteService.doRemoteFunction(10);
+    assertEquals(RemoteServiceInterface.FAILURE, result);
+  }
+
+  @Test
+  public void testSuccessfulCall() {
+    RemoteService remoteService = new RemoteService(
+        new StaticRandomProvider(0.2));
+    long result = remoteService.doRemoteFunction(10);
+    assertEquals(100, result);
+  }
+
+  private class StaticRandomProvider implements RandomProvider {
+    private double value;
+
+    StaticRandomProvider(double value) {
+      this.value = value;
+    }
+
+    @Override
+    public double random() {
+      return value;
+    }
   }
 }
diff --git a/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java b/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java
index 432df9f..72e7106 100644
--- a/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java
+++ b/ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java
@@ -24,6 +24,8 @@ package com.iluwatar.ambassador;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 /**
  * Test for {@link ServiceAmbassador}
  */
@@ -32,6 +34,6 @@ public class ServiceAmbassadorTest {
   @Test
   public void test() {
     long result = new ServiceAmbassador().doRemoteFunction(10);
-    assert result == 100 || result == -1;
+    assertTrue(result == 100 || result == RemoteServiceInterface.FAILURE);
   }
 }