Code refactor for ADTFraction improvements (#3016)

Fix #3015

Co-authored-by: Yang Libin <szuyanglb@outlook.com>

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

@@ -0,0 +1,52 @@
+package com.thealgorithms.maths;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class ADTFractionTest {
+
+    private final ADTFraction fraction1 = new ADTFraction(3, 5);
+    private final ADTFraction fraction2 = new ADTFraction(7, 8);
+
+    @Test
+    void testConstructorWithDenominatorEqualToZero() {
+        Exception exception = assertThrows(IllegalArgumentException.class, () -> new ADTFraction(1, 0));
+        assertEquals("Denominator cannot be 0", exception.getMessage());
+    }
+
+    @Test
+    public void testPlus() {
+        assertEquals(new ADTFraction(59, 40), fraction1.plus(fraction2));
+    }
+
+    @Test
+    public void testTimes() {
+        assertEquals(new ADTFraction(12, 5), fraction1.times(4));
+        assertEquals(new ADTFraction(21, 40), fraction1.times(fraction2));
+    }
+
+    @Test
+    public void testReciprocal() {
+        assertEquals(new ADTFraction(5, 3), fraction1.reciprocal());
+    }
+
+    @Test
+    public void testValue() {
+        assertEquals(0.6F, fraction1.value());
+    }
+
+    @Test
+    public void testEqualsAndHashCode() {
+        ADTFraction fraction3 = new ADTFraction(3, 5);
+        assertTrue(fraction1.equals(fraction3) && fraction3.equals(fraction1));
+        assertEquals(fraction1.hashCode(), fraction3.hashCode());
+    }
+
+    @Test
+    public void testToString() {
+        assertEquals("3/5", fraction1.toString());
+    }
+}