Add new tests

src/test/java/be/cylab/java/roc/UtilsTest.java

+package be.cylab.java.roc;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class UtilsTest {
+
+    List<Point> points;
+
+    @BeforeEach
+    void setUp() {
+        points = new ArrayList<>();
+        Random rnd = new Random(5875);
+        for (int i = 0; i < 30; i++) {
+            double score = rnd.nextDouble();
+            if (rnd.nextDouble() < 0.5) {
+                points.add(new Point(score, false));
+            } else {
+                points.add(new Point(score, true));
+            }
+        }
+    }
+
+    @AfterEach
+    void tearDown() {
+    }
+
+    @Test
+    void testCountPositiveExamples() {
+        assertEquals(20, Utils.countPositiveExamples(points));
+    }
+
+    @Test
+    void testCountNegativeExamples() {
+        assertEquals(10, Utils.countNegativeExamples(points));
+    }
+}
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