package com.example;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Timeout;

import java.time.Duration;

import static org.junit.jupiter.api.Assertions.*;

import com.example.Fibonacci;

public class FibonacciTest {
    private Fibonacci instance;

    @BeforeEach
    void setUp() {
        // The fibonacci method is static, but create an instance as required.
        instance = new Fibonacci();
    }

    @Test
    void testZero_returnsZero() {
        assertEquals(0L, instance.fibonacci(0), "Fibonacci(0) should be 0");
    }

    @Test
    void testOne_returnsOne() {
        assertEquals(1L, instance.fibonacci(1), "Fibonacci(1) should be 1");
    }

    @Test
    void testTwo_returnsOne() {
        assertEquals(1L, instance.fibonacci(2), "Fibonacci(2) should be 1");
    }

    @Test
    void testTen_returnsFiftyFive() {
        assertEquals(55L, instance.fibonacci(10), "Fibonacci(10) should be 55");
    }

    @Test
    void testThirty_returnsEightHundredThirtyTwoThousandForty() {
        assertEquals(832040L, instance.fibonacci(30), "Fibonacci(30) should be 832040");
    }

    @Test
    void testForty_returnsOneZeroTwoThreeThreeFourOneFiveFive() {
        assertEquals(102334155L, instance.fibonacci(40), "Fibonacci(40) should be 102334155");
    }

    @Test
    void testNegative_throwsIllegalArgumentException() {
        assertThrows(IllegalArgumentException.class, () -> instance.fibonacci(-1),
                "Negative input should throw IllegalArgumentException");
    }

    @Test
    void testNullInteger_throwsNullPointerException() {
        // The method accepts a primitive int, but passing an Integer that is null
        // will cause an auto-unboxing NullPointerException at the call site.
        Integer n = null;
        assertThrows(NullPointerException.class, () -> instance.fibonacci(n),
                "Passing a null Integer (auto-unboxed to int) should throw NullPointerException");
    }

    @Test
    void testNinetyTwo_returnsKnownBoundaryValue() {
        // F(92) is the largest Fibonacci number that fits in a signed 64-bit long
        assertEquals(7540113804746346429L, instance.fibonacci(92),
                "Fibonacci(92) should match the known 64-bit boundary value");
    }

    @Test
    void testNinetyThree_overflowsProducesNonPositiveValue() {
        // F(93) overflows signed 64-bit long; assert overflow manifests (value not greater than F(92))
        long f93 = instance.fibonacci(93);
        assertTrue(f93 < 0 || f93 < instance.fibonacci(92),
                "Fibonacci(93) should overflow the long range (expected non-positive or less than Fibonacci(92))");
    }

    @Test
    void testPerformance_forty_completesWithinTwoSeconds() {
        // Verify performance for a moderately large input using the naive recursive implementation.
        assertTimeout(Duration.ofSeconds(2), () -> instance.fibonacci(40));
    }
}

package com.example;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.time.Duration;

import static org.junit.jupiter.api.Assertions.*;

import com.example.Fibonacci;

public class FibonacciTest {
    private Fibonacci instance;

    @BeforeEach
    void setUp() {
        instance = new Fibonacci();
    }

    @Test
    void testZero_returnsZero() {
        // 0th Fibonacci number should be 0
        assertEquals(0L, instance.fibonacci(0));
    }

    @Test
    void testOne_returnsOne() {
        // 1st Fibonacci number should be 1
        assertEquals(1L, instance.fibonacci(1));
    }

    @Test
    void testTwo_returnsOne() {
        // 2nd Fibonacci number should be 1
        assertEquals(1L, instance.fibonacci(2));
    }

    @Test
    void testTen_returnsFiftyFive() {
        // Typical use case: 10th Fibonacci = 55
        assertEquals(55L, instance.fibonacci(10));
    }

    @Test
    void testTwenty_returns6765() {
        // Larger typical input: 20th Fibonacci = 6765
        assertEquals(6765L, instance.fibonacci(20));
    }

    @Test
    void testNegative_throwsIllegalArgumentException() {
        // Error condition: negative input should throw
        assertThrows(IllegalArgumentException.class, () -> instance.fibonacci(-1));
    }

    @Test
    void testLargeInput_completesWithinTimeout_andReturnsExpectedValue() {
        // Performance verification for a relatively large input.
        // The recursive implementation is exponential, so pick a value that's large
        // enough to be meaningful but small enough to complete in a short time on CI.
        // fibonacci(35) = 9227465
        assertTimeout(Duration.ofSeconds(2), () -> {
            long result = instance.fibonacci(35);
            assertEquals(9227465L, result);
        });
    }
}