LargestSeriesProductCalculatorTest.java

import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatExceptionOfType;

public class LargestSeriesProductCalculatorTest {

    @Test
    @DisplayName("finds the largest product if span equals length")
    public void testCorrectlyCalculatesLargestProductWhenSeriesLengthEqualsStringToSearchLength() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("29");
        long expectedProduct = 18;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(2);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("can find the largest product of 2 with numbers in order")
    public void testCorrectlyCalculatesLargestProductOfLengthTwoWithNumbersInOrder() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0123456789");
        long expectedProduct = 72;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(2);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("can find the largest product of 2")
    public void testCorrectlyCalculatesLargestProductOfLengthTwoWithNumbersNotInOrder() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("576802143");
        long expectedProduct = 48;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(2);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("can find the largest product of 3 with numbers in order")
    public void testCorrectlyCalculatesLargestProductOfLengthThreeWithNumbersInOrder() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0123456789");
        long expectedProduct = 504;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(3);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("can find the largest product of 3")
    public void testCorrectlyCalculatesLargestProductOfLengthThreeWithNumbersNotInOrder() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("1027839564");
        long expectedProduct = 270;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(3);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("can find the largest product of 5 with numbers in order")
    public void testCorrectlyCalculatesLargestProductOfLengthFiveWithNumbersInOrder() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0123456789");
        long expectedProduct = 15120;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(5);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("can get the largest product of a big number")
    public void testCorrectlyCalculatesLargestProductInLongStringToSearchV1() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator(
                "73167176531330624919225119674426574742355349194934");

        long expectedProduct = 23520;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(6);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("reports zero if the only digits are zero")
    public void testCorrectlyCalculatesLargestProductOfZeroIfAllDigitsAreZeroes() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("0000");
        long expectedProduct = 0;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(2);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("reports zero if all spans include zero")
    public void testCorrectlyCalculatesLargestProductOfZeroIfAllSeriesOfGivenLengthContainZero() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("99099");
        long expectedProduct = 0;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(3);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("rejects span longer than string length")
    public void testSeriesLengthLongerThanLengthOfStringToTestIsRejected() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("123");

        assertThatExceptionOfType(IllegalArgumentException.class)
                .isThrownBy(() -> calculator.calculateLargestProductForSeriesLength(4))
                .withMessage("Series length must be less than or equal to the length of the string to search.");
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("reports 1 for empty string and empty product (0 span)")
    public void testEmptyStringToSearchAndSeriesOfNonZeroLengthIsRejected() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("");

        assertThatExceptionOfType(IllegalArgumentException.class)
                .isThrownBy(() -> calculator.calculateLargestProductForSeriesLength(1))
                .withMessage("Series length must be less than or equal to the length of the string to search.");
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("rejects invalid character in digits")
    public void testStringToSearchContainingNonDigitCharacterIsRejected() {
        assertThatExceptionOfType(IllegalArgumentException.class)
                .isThrownBy(() -> new LargestSeriesProductCalculator("1234a5"))
                .withMessage("String to search may only contain digits.");
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("rejects negative span")
    public void testNegativeSeriesLengthIsRejected() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("12345");

        assertThatExceptionOfType(IllegalArgumentException.class)
                .isThrownBy(() -> calculator.calculateLargestProductForSeriesLength(-1))
                .withMessage("Series length must be non-negative.");
    }

    @Disabled("Remove to run test")
    @Test
    @DisplayName("integer overflow")
    public void testForIntegerOverflow() {
        LargestSeriesProductCalculator calculator = new LargestSeriesProductCalculator("9999999999");
        long expectedProduct = 3486784401L;

        long actualProduct = calculator.calculateLargestProductForSeriesLength(10);

        assertThat(actualProduct).isEqualTo(expectedProduct);
    }

}