The same remarks apply as for “Refactoring the Traditional for Loop”
- No
init() - Classes under test implement a common interface that is called in tests.
- Negative tests which apply for input less than 1900, resulting in exceptions.
package chapter11;
import org.junit.jupiter.api.Test;
import java.time.Year;
import java.util.stream.IntStream;
import static org.junit.jupiter.api.Assertions.*;
// Everything is inside the MoreComplexLoopTest class for convenience.
// Documentation for java.time.Year.isLeap()
// https://docs.oracle.com/javase/8/docs/api/java/time/Year.html#isLeap--
public class MoreComplexLoopTest {
interface LeapYears {
int countFrom1900(int upTo);
}
static class LeapYearCountBefore implements LeapYears {
public int countFrom1900(int upTo) {
if (upTo < 1900) {
throw new IllegalArgumentException("The passed value is < 1900: " + upTo);
}
int count = 0;
for (int year = 1900; year <= upTo; year += 4) {
if (Year.isLeap(year)) {
count++;
}
}
return count;
}
}
static class LeapYearCountAfter implements LeapYears {
public int countFrom1900(int upTo) {
if (upTo < 1900) {
throw new IllegalArgumentException("The passed value is < 1900: " + upTo);
}
return (int) IntStream.iterate(1900, year -> year <= upTo, year -> year + 4)
.filter(Year::isLeap)
.count();
}
}
private static void commonLeapYearsTests(final LeapYears leapYears) {
assertAll(
() -> assertEquals(0, leapYears.countFrom1900(1900)),
() -> assertEquals(25, leapYears.countFrom1900(2000)),
() -> assertEquals(27, leapYears.countFrom1900(2010)),
() -> assertEquals(31, leapYears.countFrom1900(2025)),
() -> assertEquals(49, leapYears.countFrom1900(2100)),
() -> assertEquals(267, leapYears.countFrom1900(3000)),
() -> assertThrows(IllegalArgumentException.class, () -> leapYears.countFrom1900(1800))
);
}
@Test
void leapYearCountBefore() {
commonLeapYearsTests(new LeapYearCountBefore());
}
@Test
void leapYearCountAfter() {
commonLeapYearsTests(new LeapYearCountAfter());
}
}