Add Liouville lambda function (#3284)

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

@@ -0,0 +1,66 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class LiouvilleLambdaFunctionTest {
+
+	@Test
+	void testLiouvilleLambdaMustThrowExceptionIfNumberIsZero() {
+		//given
+		int number = 0;
+		String expectedMessage = "Number must be greater than zero.";
+
+		//when
+		Exception exception = assertThrows(IllegalArgumentException.class, () -> {
+			LiouvilleLambdaFunction.liouvilleLambda(number);
+		});
+		String actualMessage = exception.getMessage();
+
+		//then
+		assertEquals(expectedMessage, actualMessage);
+	}
+
+	@Test
+	void testLiouvilleLambdaMustThrowExceptionIfNumberIsNegative() {
+		//given
+		int number = -1;
+		String expectedMessage = "Number must be greater than zero.";
+
+		//when
+		Exception exception = assertThrows(IllegalArgumentException.class, () -> {
+			LiouvilleLambdaFunction.liouvilleLambda(number);
+		});
+		String actualMessage = exception.getMessage();
+
+		//then
+		assertEquals(expectedMessage, actualMessage);
+	}
+
+	@Test
+	void testLiouvilleLambdaMustReturnNegativeOne() {
+		//given
+		int number = 11;
+		int expectedOutput = -1;
+
+		//when
+		int actualOutput = LiouvilleLambdaFunction.liouvilleLambda(number);
+
+		//then
+		assertEquals(expectedOutput, actualOutput);
+	}
+
+	@Test
+	void testLiouvilleLambdaMustReturnPositiveOne() {
+		//given
+		int number = 10;
+		int expectedOutput = 1;
+
+		//when
+		int actualOutput = LiouvilleLambdaFunction.liouvilleLambda(number);
+
+		//then
+		assertEquals(expectedOutput, actualOutput);
+	}
+}