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import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import org.junit.runners.JUnit4;
import java.util.Random;
import java.util.Arrays;
public class SolutionTest {
@Test
public void basicTests() {
long[] expected = new long[] { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 };
assertArrayEquals("All the ones", expected, PascalDiagonals.generateDiagonal(0, 10));
expected = new long[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
assertArrayEquals("Natural numbers", expected, PascalDiagonals.generateDiagonal(1, 10));
expected = new long[] { 1, 3, 6, 10, 15, 21, 28, 36, 45, 55 };
assertArrayEquals("Triangular numbers", expected, PascalDiagonals.generateDiagonal(2, 10));
expected = new long[] { 1, 4, 10, 20, 35, 56, 84, 120, 165, 220 };
assertArrayEquals("Tetrahedral numbers", expected, PascalDiagonals.generateDiagonal(3, 10));
expected = new long[] { 1, 5, 15, 35, 70, 126, 210, 330, 495, 715 };
assertArrayEquals("Pentatope numbers", expected, PascalDiagonals.generateDiagonal(4, 10));
}
@Test
public void edgeCases() {
assertArrayEquals("Array length zero", new long[] {}, PascalDiagonals.generateDiagonal(10, 0));
long[] expected = new long[] { 1, 101, 5151, 176851, 4598126, 96560646 };
assertArrayEquals("Late row, short array", expected, PascalDiagonals.generateDiagonal(100, 6));
}
@Test
public void randomTests() {
Random r = new Random();
for (int i = 0; i < 100; i++) {
int n = r.nextInt(26) + 25;
int l = r.nextInt(6) + 10;
assertArrayEquals("Random " + i, generateDiagonal(n, l), PascalDiagonals.generateDiagonal(n, l));
}
}
private static long[] generateDiagonal(int n, int l) {
long[] diagonal = new long[l];
Arrays.fill(diagonal, 1);
for (int i = 1; i < l; i++)
diagonal[i] = diagonal[i - 1] * (n + i) / i;
return diagonal;
}
}
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