Testing and fixing

.classpath

@@ -24,5 +24,6 @@
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/4"/>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>

src/main/java/morlok8k/MinecraftLandGenerator/World.java

@@ -6,6 +6,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -188,9 +189,10 @@ public class World {
 	}
 
 	private static List<Integer> generateLinearSpawnpoints(int start, int length, int maxStep) {
-		int stepCount = (int) Math.ceil((double) length / maxStep);
+		double stepCount = Math.ceil((double) length / maxStep);
+		if (stepCount == 0) return Arrays.asList(start);
 		double realStep = length / stepCount;
-		return IntStream.rangeClosed(0, stepCount).mapToObj(i -> start + (int) (realStep * i))
+		return IntStream.rangeClosed(0, (int) stepCount).mapToObj(i -> start + (int) (realStep * i))
 				.collect(Collectors.toList());
 	}
 }

src/test/java/SpawnpointTest.java

@@ -0,0 +1,50 @@
+import static org.junit.Assert.assertTrue;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.joml.Vector2i;
+import org.junit.Test;
+
+import morlok8k.MinecraftLandGenerator.World;
+
+public class SpawnpointTest {
+
+	static {
+		System.setProperty("joml.format", "false");
+	}
+
+	@Test
+	public void simpleTest() {
+		test(0, 0, 25, 25, 25);
+		test(-100, 10, 500, 400, 25);
+		test(-256, 16, 512, 256, 25);
+		test(-255, 15, 512, 256, 25);
+		test(-256, 16, 511, 255, 25);
+		test(-255, 15, 511, 255, 25);
+		test(25, 24, 50, 49, 25);
+		test(25, 24, 49, 50, 25);
+	}
+
+	private static void test(int startX, int startZ, int width, int height, int increment) {
+		List<Vector2i> spawn = World.generateSpawnpoints(startX, startZ, width, height, increment);
+		int margin = increment / 2;
+		Set<Vector2i> coverage = new HashSet<>();
+		for (Vector2i v : spawn) {
+			for (int z = v.y - margin; z <= v.y + margin; z++)
+				for (int x = v.x - margin; x <= v.x + margin; x++)
+					coverage.add(new Vector2i(x, z));
+		}
+		for (int z = startZ; z < startZ + height; z++) {
+			for (int x = startX; x < startX + width; x++) {
+				assertTrue(
+						"Chunk (" + x + ", " + z + ") in (" + startX + ", " + startZ + ", " + width
+								+ ", " + height
+								+ ") should be covered the spawn chunks, but they were " + spawn,
+						coverage.remove(new Vector2i(x, z)));
+			}
+		}
+		assertTrue(coverage.isEmpty());
+	}
+}