refactor: Enhance docs, code, add tests in KeithNumber (#6748)

* refactor: Enhance docs, code, add tests in `KeithNumber` * Fix --------- Co-authored-by: a <alexanderklmn@gmail.com>
2025-12-19 07:00:35 +08:00 · 2025-10-13 03:07:24 +05:30
parent 297634d05f
commit 387ecef310
2 changed files with 231 additions and 37 deletions
--- a/src/test/java/com/thealgorithms/maths/KeithNumberTest.java
+++ b/src/test/java/com/thealgorithms/maths/KeithNumberTest.java
@@ -0,0 +1,153 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test cases for {@link KeithNumber}.
+ */
+class KeithNumberTest {
+
+    /**
+     * Tests single-digit Keith numbers.
+     * All single-digit numbers (1-9) are Keith numbers by definition.
+     */
+    @Test
+    void testSingleDigitKeithNumbers() {
+        assertTrue(KeithNumber.isKeith(1));
+        assertTrue(KeithNumber.isKeith(2));
+        assertTrue(KeithNumber.isKeith(3));
+        assertTrue(KeithNumber.isKeith(4));
+        assertTrue(KeithNumber.isKeith(5));
+        assertTrue(KeithNumber.isKeith(6));
+        assertTrue(KeithNumber.isKeith(7));
+        assertTrue(KeithNumber.isKeith(8));
+        assertTrue(KeithNumber.isKeith(9));
+    }
+
+    /**
+     * Tests two-digit Keith numbers.
+     * Known two-digit Keith numbers: 14, 19, 28, 47, 61, 75.
+     */
+    @Test
+    void testTwoDigitKeithNumbers() {
+        assertTrue(KeithNumber.isKeith(14));
+        assertTrue(KeithNumber.isKeith(19));
+        assertTrue(KeithNumber.isKeith(28));
+        assertTrue(KeithNumber.isKeith(47));
+        assertTrue(KeithNumber.isKeith(61));
+        assertTrue(KeithNumber.isKeith(75));
+    }
+
+    /**
+     * Tests three-digit Keith numbers.
+     * Known three-digit Keith numbers: 197, 742.
+     */
+    @Test
+    void testThreeDigitKeithNumbers() {
+        assertTrue(KeithNumber.isKeith(197));
+        assertTrue(KeithNumber.isKeith(742));
+    }
+
+    /**
+     * Tests four-digit Keith numbers.
+     * Known four-digit Keith numbers: 1104, 1537, 2208, 2580, 3684, 4788, 7385,
+     * 7647, 7909.
+     */
+    @Test
+    void testFourDigitKeithNumbers() {
+        assertTrue(KeithNumber.isKeith(1104));
+        assertTrue(KeithNumber.isKeith(1537));
+        assertTrue(KeithNumber.isKeith(2208));
+    }
+
+    /**
+     * Tests two-digit non-Keith numbers.
+     */
+    @Test
+    void testTwoDigitNonKeithNumbers() {
+        assertFalse(KeithNumber.isKeith(10));
+        assertFalse(KeithNumber.isKeith(11));
+        assertFalse(KeithNumber.isKeith(12));
+        assertFalse(KeithNumber.isKeith(13));
+        assertFalse(KeithNumber.isKeith(15));
+        assertFalse(KeithNumber.isKeith(20));
+        assertFalse(KeithNumber.isKeith(30));
+        assertFalse(KeithNumber.isKeith(50));
+    }
+
+    /**
+     * Tests three-digit non-Keith numbers.
+     */
+    @Test
+    void testThreeDigitNonKeithNumbers() {
+        assertFalse(KeithNumber.isKeith(100));
+        assertFalse(KeithNumber.isKeith(123));
+        assertFalse(KeithNumber.isKeith(196));
+        assertFalse(KeithNumber.isKeith(198));
+        assertFalse(KeithNumber.isKeith(456));
+        assertFalse(KeithNumber.isKeith(741));
+        assertFalse(KeithNumber.isKeith(743));
+        assertFalse(KeithNumber.isKeith(999));
+    }
+
+    /**
+     * Tests validation for edge case 14 in detail.
+     * 14 is a Keith number: 1, 4, 5 (1+4), 9 (4+5), 14 (5+9).
+     */
+    @Test
+    void testKeithNumber14() {
+        assertTrue(KeithNumber.isKeith(14));
+    }
+
+    /**
+     * Tests validation for edge case 197 in detail.
+     * 197 is a Keith number: 1, 9, 7, 17, 33, 57, 107, 197.
+     */
+    @Test
+    void testKeithNumber197() {
+        assertTrue(KeithNumber.isKeith(197));
+    }
+
+    /**
+     * Tests that zero throws an IllegalArgumentException.
+     */
+    @Test
+    void testZeroThrowsException() {
+        assertThrows(IllegalArgumentException.class, () -> KeithNumber.isKeith(0));
+    }
+
+    /**
+     * Tests that negative numbers throw an IllegalArgumentException.
+     */
+    @Test
+    void testNegativeNumbersThrowException() {
+        assertThrows(IllegalArgumentException.class, () -> KeithNumber.isKeith(-1));
+        assertThrows(IllegalArgumentException.class, () -> KeithNumber.isKeith(-14));
+        assertThrows(IllegalArgumentException.class, () -> KeithNumber.isKeith(-100));
+    }
+
+    /**
+     * Tests various edge cases with larger numbers.
+     */
+    @Test
+    void testLargerNumbers() {
+        assertTrue(KeithNumber.isKeith(2208));
+        assertFalse(KeithNumber.isKeith(2207));
+        assertFalse(KeithNumber.isKeith(2209));
+    }
+
+    /**
+     * Tests the expected behavior with all two-digit Keith numbers.
+     */
+    @Test
+    void testAllKnownTwoDigitKeithNumbers() {
+        int[] knownKeithNumbers = {14, 19, 28, 47, 61, 75};
+        for (int number : knownKeithNumbers) {
+            assertTrue(KeithNumber.isKeith(number), "Expected " + number + " to be a Keith number");
+        }
+    }
+}