Java/src/test/java/com/thealgorithms/maths/FactorialTest.java at master · TheAlgorithms/Java · GitHub

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packagecom.thealgorithms.maths;

importstaticorg.junit.jupiter.api.Assertions.assertEquals;
importstaticorg.junit.jupiter.api.Assertions.assertThrows;

importjava.math.BigInteger;
importorg.junit.jupiter.api.Test;

publicclassFactorialTest {
privatestaticfinalStringEXCEPTION_MESSAGE = "Input number cannot be negative";

@Test
publicvoidtestWhenInvalidInoutProvidedShouldThrowException() {
IllegalArgumentExceptionexception = assertThrows(IllegalArgumentException.class, () -> Factorial.factorial(-1));
assertEquals(EXCEPTION_MESSAGE, exception.getMessage());
 }

@Test
publicvoidtestCorrectFactorialCalculation() {
assertEquals(BigInteger.ONE, Factorial.factorial(0));
assertEquals(BigInteger.ONE, Factorial.factorial(1));
assertEquals(BigInteger.valueOf(120), Factorial.factorial(5));
assertEquals(BigInteger.valueOf(3628800), Factorial.factorial(10));
 }
}