Make changes in DynamicSpeedTrackPathDescriptor :

Add field: CriticalDifference
Add helper method isDifferenceSignificant to test needsRedraw
Add getSpeedMargin,setAverageMovingSpeed getAverageMovingSpeed methods
Change some code style of DynamicSpeedTrackPathDescriptor

Add test cases for FixedSpeedTrackPathDescriptor and DynamicSpeedTrackPathDescriptor

MyTracks/src/com/google/android/apps/mytracks/maps/DynamicSpeedTrackPathDescriptor.java

@@ -22,34 +22,36 @@ import com.google.android.apps.mytracks.content.MyTracksProviderUtils;
 import com.google.android.apps.mytracks.content.Track;
 import com.google.android.apps.mytracks.stats.TripStatistics;
 import com.google.android.maps.mytracks.R;
+import com.google.common.annotations.VisibleForTesting;
 
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
 import android.util.Log;
 
-
 /**
  * A dynamic speed path descriptor.
- *
+ * 
  * @author Vangelis S.
  */
-public class DynamicSpeedTrackPathDescriptor 
-  implements TrackPathDescriptor, OnSharedPreferenceChangeListener {
-  
+public class DynamicSpeedTrackPathDescriptor implements TrackPathDescriptor,
+    OnSharedPreferenceChangeListener {
+
   private int slowSpeed;
   private int normalSpeed;
   private int speedMargin;
   private final int speedMarginDefault;
   private double averageMovingSpeed;
   private final Context context;
-  
-  public DynamicSpeedTrackPathDescriptor(Context context){
+  @VisibleForTesting
+  static final int CRITICAL_DIFFERENCE_PERCENTAGE = 20;
+
+  public DynamicSpeedTrackPathDescriptor(Context context) {
     this.context = context;
-    speedMarginDefault = Integer.parseInt(
-        context.getString(R.string.color_mode_dynamic_percentage_default));
-    SharedPreferences prefs = context.getSharedPreferences(
-        Constants.SETTINGS_NAME, Context.MODE_PRIVATE);
+    speedMarginDefault = Integer.parseInt(context
+        .getString(R.string.color_mode_dynamic_percentage_default));
+    SharedPreferences prefs = context.getSharedPreferences(Constants.SETTINGS_NAME,
+        Context.MODE_PRIVATE);
 
     if (prefs == null) {
       speedMargin = speedMarginDefault;
@@ -60,7 +62,8 @@ public class DynamicSpeedTrackPathDescriptor
     speedMargin = getSpeedMargin(prefs);
   }
 
-  private int getSpeedMargin(SharedPreferences sharedPreferences) {
+  @VisibleForTesting
+  int getSpeedMargin(SharedPreferences sharedPreferences) {
     try {
       return Integer.parseInt(sharedPreferences.getString(
           context.getString(R.string.track_color_mode_dynamic_speed_variation_key),
@@ -72,34 +75,32 @@ public class DynamicSpeedTrackPathDescriptor
 
   /**
    * Get the slow speed calculated based on the % below the average speed.
+   * 
    * @return The speed limit considered as slow.
    */
-  public int getSlowSpeed()
-  {
-    slowSpeed = (int) (averageMovingSpeed - (averageMovingSpeed * speedMargin / 100)); 
+  public int getSlowSpeed() {
+    slowSpeed = (int) (averageMovingSpeed - (averageMovingSpeed * speedMargin / 100));
     return slowSpeed;
   }
-  
+
   /**
-   * Get the medium speed calculated based on the % above the average speed.
+   * Gets the medium speed calculated based on the % above the average speed.
+   * 
    * @return The speed limit considered as normal.
    */
-  public int getNormalSpeed()
-  {
-    normalSpeed = (int) (averageMovingSpeed + (averageMovingSpeed * speedMargin / 100)); 
+  public int getNormalSpeed() {
+    normalSpeed = (int) (averageMovingSpeed + (averageMovingSpeed * speedMargin / 100));
     return normalSpeed;
   }
-  
+
   @Override
   public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
     Log.d(TAG, "DynamicSpeedTrackPathDescriptor: onSharedPreferences changed " + key);
-    if (key == null 
-    	|| !key.equals(context.getString(R.string.track_color_mode_dynamic_speed_variation_key))) {
-      return;
-    }
-    SharedPreferences prefs = context.getSharedPreferences(
-        Constants.SETTINGS_NAME, Context.MODE_PRIVATE);
-    	
+    if (key == null
+        || !key.equals(context.getString(R.string.track_color_mode_dynamic_speed_variation_key))) { return; }
+    SharedPreferences prefs = context.getSharedPreferences(Constants.SETTINGS_NAME,
+        Context.MODE_PRIVATE);
+
     if (prefs == null) {
       speedMargin = speedMarginDefault;
       return;
@@ -110,33 +111,69 @@ public class DynamicSpeedTrackPathDescriptor
 
   @Override
   public boolean needsRedraw() {
-    SharedPreferences prefs = context.getSharedPreferences(
-        Constants.SETTINGS_NAME, Context.MODE_PRIVATE);
+    SharedPreferences prefs = context.getSharedPreferences(Constants.SETTINGS_NAME,
+        Context.MODE_PRIVATE);
     long currentTrackId = prefs.getLong(context.getString(R.string.selected_track_key), -1);
-    if(currentTrackId == -1) {
-      // Could not find track. 
-      return false; 
+    if (currentTrackId == -1) {
+      // Could not find track.
+      return false;
     }
     Track track = MyTracksProviderUtils.Factory.get(context).getTrack(currentTrackId);
     TripStatistics stats = track.getStatistics();
-    double newaverageSpeed = (int) Math.floor(stats.getAverageMovingSpeed() * 3.6);
-    
-    if(averageMovingSpeed == 0) {
-      averageMovingSpeed = newaverageSpeed;
-      return true;
-    }
-    
-    double difference = Math.max(averageMovingSpeed, newaverageSpeed);
+    double newAverageMovingSpeed = (int) Math.floor(stats.getAverageMovingSpeed() * 3.6);
 
-    if (difference == 0.0) {
-      difference = 0.0;
-    } else {
-      difference = Math.abs(averageMovingSpeed - newaverageSpeed) / difference * 100;
+    return isDifferenceSignificant(averageMovingSpeed, newAverageMovingSpeed);
+  }
+
+  /**
+   * Checks whether the old speed and the new speed differ significantly or not.
+   */
+  public boolean isDifferenceSignificant(double oldAverageMovingSpeed, double newAverageMovingSpeed) {
+    if (oldAverageMovingSpeed == 0) {
+      if (newAverageMovingSpeed == 0) {
+        return false;
+      } else {
+        averageMovingSpeed = newAverageMovingSpeed;
+        return true;
+      }
     }
-    if(difference >= 20) {
-      averageMovingSpeed = newaverageSpeed;
+
+    // Here, both oldAverageMovingSpeed and newAverageMovingSpeed are not zero.
+    double maxValue = Math.max(oldAverageMovingSpeed, newAverageMovingSpeed);
+    double differencePercentage = Math.abs(oldAverageMovingSpeed - newAverageMovingSpeed)
+        / maxValue * 100;
+    if (differencePercentage >= CRITICAL_DIFFERENCE_PERCENTAGE) {
+      averageMovingSpeed = newAverageMovingSpeed;
       return true;
     }
     return false;
   }
+
+  /**
+   * Gets the value of variable speedMargin to check the result of test.  
+   * @return the value of speedMargin.
+   */
+  @VisibleForTesting
+  int getSpeedMargin() {
+    return speedMargin;
+  }
+
+  /**
+   * Sets the value of newAverageMovingSpeed to test the method isDifferenceSignificant.
+   * @param newAverageMovingSpeed the value to set.
+   */
+  @VisibleForTesting
+  void setAverageMovingSpeed(double newAverageMovingSpeed) {
+    averageMovingSpeed = newAverageMovingSpeed;
+  }
+
+  /**
+   * Gets the value of averageMovingSpeed to check the result of test.
+   * 
+   * @return the value of averageMovingSpeed
+   */
+  @VisibleForTesting
+  double getAverageMovingSpeed() {
+    return averageMovingSpeed;
+  }
 }