Add tests for SkylineAlgorithm.java (#5556)

Author: Hardvan

DIRECTORY.md

@@ -725,6 +725,7 @@
               * [ZigzagTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/ZigzagTraversalTest.java)
           * divideandconquer
             * [BinaryExponentiationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/divideandconquer/BinaryExponentiationTest.java)
+            * [SkylineAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/divideandconquer/SkylineAlgorithmTest.java)
             * [StrassenMatrixMultiplicationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/divideandconquer/StrassenMatrixMultiplicationTest.java)
           * dynamicprogramming
             * [BoardPathTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/BoardPathTest.java)

src/test/java/com/thealgorithms/divideandconquer/SkylineAlgorithmTest.java

@@ -0,0 +1,102 @@
+package com.thealgorithms.divideandconquer;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class SkylineAlgorithmTest {
+
+    private SkylineAlgorithm skylineAlgorithm;
+
+    @BeforeEach
+    public void setUp() {
+        skylineAlgorithm = new SkylineAlgorithm();
+    }
+
+    @Test
+    public void testProduceSubSkyLinesSinglePoint() {
+        // Test with a single point
+        ArrayList<SkylineAlgorithm.Point> points = new ArrayList<>();
+        points.add(new SkylineAlgorithm.Point(1, 10));
+
+        ArrayList<SkylineAlgorithm.Point> result = skylineAlgorithm.produceSubSkyLines(points);
+
+        assertEquals(1, result.size());
+        assertEquals(1, result.get(0).getX());
+        assertEquals(10, result.get(0).getY());
+    }
+
+    @Test
+    public void testProduceSubSkyLinesTwoPoints() {
+        // Test with two points, one dominated by the other
+        ArrayList<SkylineAlgorithm.Point> points = new ArrayList<>();
+        points.add(new SkylineAlgorithm.Point(1, 10));
+        points.add(new SkylineAlgorithm.Point(1, 5));
+
+        ArrayList<SkylineAlgorithm.Point> result = skylineAlgorithm.produceSubSkyLines(points);
+
+        assertEquals(1, result.size());
+        assertEquals(1, result.get(0).getX());
+        assertEquals(5, result.get(0).getY());
+    }
+
+    @Test
+    public void testProduceSubSkyLinesMultiplePoints() {
+        // Test with more than two points
+        ArrayList<SkylineAlgorithm.Point> points = new ArrayList<>();
+        points.add(new SkylineAlgorithm.Point(1, 10));
+        points.add(new SkylineAlgorithm.Point(2, 15));
+        points.add(new SkylineAlgorithm.Point(3, 5));
+        points.add(new SkylineAlgorithm.Point(4, 20));
+
+        ArrayList<SkylineAlgorithm.Point> result = skylineAlgorithm.produceSubSkyLines(points);
+
+        assertEquals(2, result.size());
+
+        // Assert the correct points in skyline
+        assertEquals(1, result.get(0).getX());
+        assertEquals(10, result.get(0).getY());
+        assertEquals(3, result.get(1).getX());
+        assertEquals(5, result.get(1).getY());
+    }
+
+    @Test
+    public void testProduceFinalSkyLine() {
+        // Test merging two skylines
+        ArrayList<SkylineAlgorithm.Point> left = new ArrayList<>();
+        left.add(new SkylineAlgorithm.Point(1, 10));
+        left.add(new SkylineAlgorithm.Point(2, 5));
+
+        ArrayList<SkylineAlgorithm.Point> right = new ArrayList<>();
+        right.add(new SkylineAlgorithm.Point(3, 8));
+        right.add(new SkylineAlgorithm.Point(4, 3));
+
+        ArrayList<SkylineAlgorithm.Point> result = skylineAlgorithm.produceFinalSkyLine(left, right);
+
+        assertEquals(3, result.size());
+
+        // Assert the correct points in the final skyline
+        assertEquals(1, result.get(0).getX());
+        assertEquals(10, result.get(0).getY());
+        assertEquals(2, result.get(1).getX());
+        assertEquals(5, result.get(1).getY());
+        assertEquals(4, result.get(2).getX());
+        assertEquals(3, result.get(2).getY());
+    }
+
+    @Test
+    public void testXComparator() {
+        // Test the XComparator used for sorting the points
+        SkylineAlgorithm.XComparator comparator = new SkylineAlgorithm().new XComparator();
+
+        SkylineAlgorithm.Point p1 = new SkylineAlgorithm.Point(1, 10);
+        SkylineAlgorithm.Point p2 = new SkylineAlgorithm.Point(2, 5);
+
+        // Check if the XComparator sorts points by their x-value
+        assertEquals(-1, comparator.compare(p1, p2)); // p1.x < p2.x
+        assertEquals(1, comparator.compare(p2, p1)); // p2.x > p1.x
+        assertEquals(0, comparator.compare(p1, new SkylineAlgorithm.Point(1, 15))); // p1.x == p2.x
+    }
+}