refactor: refactor Ceil and improved tests

src/main/java/com/thealgorithms/maths/Ceil.java

@@ -1,23 +1,27 @@
 package com.thealgorithms.maths;
 
+/**
+ * Utility class to compute the ceiling of a given number.
+ */
 public final class Ceil {
+
     private Ceil() {
     }
 
     /**
-     * Returns the smallest (closest to negative infinity)
+     * Returns the smallest double value that is greater than or equal to the input.
+     * Equivalent to mathematical ⌈x⌉ (ceiling function).
      *
-     * @param number the number
-     * @return the smallest (closest to negative infinity) of given
-     * {@code number}
+     * @param number the number to ceil
+     * @return the smallest double greater than or equal to {@code number}
      */
     public static double ceil(double number) {
-        if (number - (int) number == 0) {
-            return number;
-        } else if (number - (int) number > 0) {
-            return (int) (number + 1);
+        long intPart = (long) number;
+
+        if (number > 0 && number != intPart) {
+            return intPart + 1.0;
         } else {
-            return (int) number;
+            return (double) intPart;
         }
     }
 }

src/test/java/com/thealgorithms/maths/CeilTest.java

@@ -2,16 +2,14 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 public class CeilTest {
 
-    @Test
-    void testCeil() {
-        assertEquals(8, Ceil.ceil(7.057));
-        assertEquals(8, Ceil.ceil(7.004));
-        assertEquals(-13, Ceil.ceil(-13.004));
-        assertEquals(1, Ceil.ceil(.98));
-        assertEquals(-11, Ceil.ceil(-11.357));
+    @ParameterizedTest
+    @CsvSource({"7.057, 8", "7.004, 8", "-13.004, -13", "0.98, 1", "-11.357, -11"})
+    void testCeil(double input, int expected) {
+        assertEquals(expected, Ceil.ceil(input));
     }
 }