firs step forward sucessfully

src/main/java/cat/hack3/codingtests/marsrover/Coordinates.java

@@ -1,8 +1,17 @@
 package cat.hack3.codingtests.marsrover;
 
+/**
+ * Notice that the representation is the following:
+ * Latitude is Y, starts from 0 on the top and goes down incrementally
+ * Longitude is X, starts from 0 on the left and goes to right incrementally
+ * 0  1   2   3
+ * 1  11  12  13
+ * 2  12  22  23
+ * 3  13  23  33
+ */
 public class Coordinates {
-    private final int latitude;
-    private final int longitude;
+    private int latitude;
+    private int longitude;
 
     public static Coordinates of(int latitude, int longitude) {
         return new Coordinates(latitude, longitude);
@@ -13,6 +22,11 @@ public class Coordinates {
         this.longitude = longitude;
     }
 
+    public Coordinates incrementSouth() {
+        latitude++;
+        return this;
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;

src/main/java/cat/hack3/codingtests/marsrover/MarsRover.java

@@ -2,16 +2,21 @@ package cat.hack3.codingtests.marsrover;
 
 public class MarsRover {
     private final MarsMap marsMap;
-    private final int latitudeStartingPoint;
-    private final int longitudeStartingPoint;
+    private Coordinates currentCoordinates;
+    private MarsMap.Direction currentDirection;
 
-    public MarsRover(MarsMap marsMap, int latitudeStartingPoint, int longitudeStartingPoint, MarsMap.Direction startingDirection) {
+    public MarsRover(MarsMap marsMap, Coordinates startingCoordinates, MarsMap.Direction startingDirection) {
         this.marsMap = marsMap;
-        this.latitudeStartingPoint = latitudeStartingPoint;
-        this.longitudeStartingPoint = longitudeStartingPoint;
+        currentCoordinates = startingCoordinates;
+        currentDirection = startingDirection;
     }
 
     public Coordinates moveForward() {
-        return Coordinates.of(0, 0);
+        return switch (currentDirection) {
+            case NORTH -> null;
+            case SOUTH -> currentCoordinates.incrementSouth();
+            case EAST -> null;
+            case WEST -> null;
+        };
     }
 }

src/test/java/cat/hack3/codingtests/marsrover/MarsRoverTest.java

@@ -19,7 +19,8 @@ public class MarsRoverTest {
 
         int latitudeStartingPoint = 2;
         int longitudeStartingPoint = 3;
-        rover = new MarsRover(marsMap, latitudeStartingPoint, longitudeStartingPoint, SOUTH);
+        var startingCoordinates = Coordinates.of(latitudeStartingPoint, longitudeStartingPoint);
+        rover = new MarsRover(marsMap, startingCoordinates, SOUTH);
     }
 
     @Test