Add tests Tower of Hanoi

src/test/java/com/thealgorithms/others/TowerOfHanoiTest.java

@@ -0,0 +1,51 @@
+package com.thealgorithms.others;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class TowerOfHanoiTest {
+
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+    private final PrintStream standardOut = System.out;
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+    }
+
+    @AfterEach
+    public void tearDown() {
+        System.setOut(standardOut);
+    }
+
+    @Test
+    public void testShiftWithNullDiscs() {
+        TowerOfHanoi.shift(1, null, null, null);
+        String expectedOutput = "Move 1 from null to null\n";
+        assertEquals(expectedOutput, outputStreamCaptor.toString());
+    }
+
+    @Test
+    public void testShiftWithNegativeMove() {
+        assertThrows(StackOverflowError.class, () -> { TowerOfHanoi.shift(-1, "A", "B", "C"); });
+    }
+
+    @Test
+    public void testShiftWithThreeDiscs() {
+        TowerOfHanoi.shift(3, "A", "B", "C");
+        String expectedOutput = "Move 1 from A to C\n"
+            + "Move 2 from A to B\n"
+            + "Move 1 from C to B\n"
+            + "Move 3 from A to C\n"
+            + "Move 1 from B to A\n"
+            + "Move 2 from B to C\n"
+            + "Move 1 from A to C\n";
+        assertEquals(expectedOutput, outputStreamCaptor.toString());
+    }
+}