diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index 1eb319e..0748042 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -14,12 +14,16 @@ jobs:
         ]
 
     steps:
+      - name: Select java runtime version
+        run: sudo update-java-alternatives --set $JAVA_HOME_21_X64
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
-        run: pip install pillow
+        run: pip install pillow pytest
+      - name: Pregenerate minecraft worlds
+        run: python -m tests.sample_server
       - name: Run tests
-        run: python tests/alltests.py
+        run: pytest
diff --git a/examples/biome_analysis.py b/examples/biome_analysis.py
index 12c32a3..753ef25 100755
--- a/examples/biome_analysis.py
+++ b/examples/biome_analysis.py
@@ -3,7 +3,6 @@
 Counter the number of biomes in the world. Works only for Anvil-based world folders.
 """
 import locale, os, sys
-from struct import pack, unpack
 
 # local module
 try:
@@ -14,9 +13,7 @@
     if not os.path.exists(os.path.join(extrasearchpath,'nbt')):
         raise
     sys.path.append(extrasearchpath)
-from nbt.region import RegionFile
-from nbt.chunk import Chunk
-from nbt.world import AnvilWorldFolder,UnknownWorldFormat
+from nbt.world import AnvilWorldFolder
 
 BIOMES = {
     0 : "Ocean",
diff --git a/examples/block_analysis.py b/examples/block_analysis.py
index cc79ce8..33adb9c 100755
--- a/examples/block_analysis.py
+++ b/examples/block_analysis.py
@@ -107,7 +107,7 @@ def print_results():
         print(locale.format_string("%20s: %12d", (block_id, block_count)))
         block_total += block_count
     
-    solid_blocks = block_total - block_counts ['air']
+    solid_blocks = block_total - block_counts['minecraft:air']
     solid_ratio = (solid_blocks+0.0)/block_total
     print(locale.format_string("%d total blocks in world, %d are non-air (%0.4f", (block_total, solid_blocks, 100.0*solid_ratio))+"%)")
 
diff --git a/examples/chest_analysis.py b/examples/chest_analysis.py
index 1da204b..cef49c7 100755
--- a/examples/chest_analysis.py
+++ b/examples/chest_analysis.py
@@ -51,21 +51,7 @@ def chests_per_chunk(chunk):
 
     chests = []
 
-    for entity in chunk['Entities']:
-        eid = entity["id"].value
-        if eid == "Minecart" and entity["type"].value == 1 or eid == "minecraft:chest_minecart":
-            x,y,z = entity["Pos"]
-            x,y,z = x.value,y.value,z.value
-
-            # Treasures are empty upon first opening
-
-            try:
-                items = items_from_nbt(entity["Items"])
-            except KeyError:
-                items = {}
-            chests.append(Chest("Minecart with chest",(x,y,z),items))
-
-    for entity in chunk['TileEntities']:
+    for entity in chunk['block_entities']:
         eid = entity["id"].value
         if eid == "Chest" or eid == "minecraft:chest":
             x,y,z = entity["x"].value,entity["y"].value,entity["z"].value
@@ -103,7 +89,7 @@ def main(world_folder):
     
     try:
         for chunk in world.iter_nbt():
-            print_results(chests_per_chunk(chunk["Level"]))
+            print_results(chests_per_chunk(chunk))
 
     except KeyboardInterrupt:
         return 75 # EX_TEMPFAIL
diff --git a/examples/map.py b/examples/map.py
index 817503f..9863425 100755
--- a/examples/map.py
+++ b/examples/map.py
@@ -15,9 +15,7 @@
     if not os.path.exists(os.path.join(extrasearchpath,'nbt')):
         raise
     sys.path.append(extrasearchpath)
-from nbt.region import RegionFile
-from nbt.chunk import Chunk
-from nbt.world import WorldFolder,McRegionWorldFolder
+from nbt.world import WorldFolder
 # PIL module (not build-in)
 try:
     from PIL import Image
@@ -73,6 +71,7 @@ def get_heightmap_image(chunk, buffer=False, gmin=False, gmax=False):
 #    'redstone_ore', 'lapis_ore', 'emerald_ore',
 #    'cobweb',
     ]
+block_ignore = [f'minecraft:{b}' for b in block_ignore]
 
 
 # Map of block colors from names
@@ -165,6 +164,10 @@ def get_heightmap_image(chunk, buffer=False, gmin=False, gmax=False):
     'wheat':                {'h':123, 's':60,  'l':50 },
     'white_wool':           {'h':0,   's':0,   'l':100},
     }
+block_colors = {
+    f'minecraft:{b}': c
+    for b, c in block_colors.items()
+}
 
 
 def get_map(chunk):
diff --git a/examples/player_print.py b/examples/player_print.py
index dfdc325..b765f1c 100755
--- a/examples/player_print.py
+++ b/examples/player_print.py
@@ -3,7 +3,7 @@
 Finds and prints different entities in a game file, including mobs, items, and vehicles.
 """
 
-import locale, os, sys
+import os, sys
 
 # local module
 try:
diff --git a/examples/regionfile_analysis.py b/examples/regionfile_analysis.py
index 4589659..656976d 100755
--- a/examples/regionfile_analysis.py
+++ b/examples/regionfile_analysis.py
@@ -3,7 +3,7 @@
 Defragment a given region file.
 """
 
-import locale, os, sys
+import os, sys
 import collections
 from optparse import OptionParser
 import gzip
diff --git a/examples/scoreboard.py b/examples/scoreboard.py
index b5e104c..a74743f 100755
--- a/examples/scoreboard.py
+++ b/examples/scoreboard.py
@@ -15,7 +15,7 @@
     if not os.path.exists(os.path.join(extrasearchpath,'nbt')):
         raise
     sys.path.append(extrasearchpath)
-from nbt.nbt import NBTFile, TAG_Long, TAG_Int, TAG_String, TAG_List, TAG_Compound
+from nbt.nbt import NBTFile
 
 def main(world_folder, show=True):
     scorefile = world_folder + '/data/scoreboard.dat'
@@ -40,4 +40,4 @@ def main(world_folder, show=True):
         print("No such folder as "+world_folder)
         sys.exit(72) # EX_IOERR
 
-    sys.exit(main(world_folder, show))
\ No newline at end of file
+    sys.exit(main(world_folder, show))
diff --git a/examples/seed.py b/examples/seed.py
index eafd2cd..6c1ca49 100755
--- a/examples/seed.py
+++ b/examples/seed.py
@@ -19,7 +19,7 @@
 def main(world_folder):
     filename = os.path.join(world_folder,'level.dat')
     level = NBTFile(filename)
-    print(level["Data"]["RandomSeed"])
+    print(level["Data"]["WorldGenSettings"]["seed"].value)
     return 0 # NOERR
 
 
diff --git a/examples/utilities.py b/examples/utilities.py
index 2f2dde0..fd61cec 100755
--- a/examples/utilities.py
+++ b/examples/utilities.py
@@ -16,7 +16,7 @@
     if not os.path.exists(os.path.join(extrasearchpath,'nbt')):
         raise
     sys.path.append(extrasearchpath)
-from nbt.nbt import NBTFile, TAG_Long, TAG_Int, TAG_String, TAG_List, TAG_Compound
+from nbt.nbt import TAG_Long, TAG_String, TAG_List, TAG_Compound
 
 def unpack_nbt(tag):
     """
diff --git a/nbt/chunk.py b/nbt/chunk.py
index a59fcc0..2c94195 100644
--- a/nbt/chunk.py
+++ b/nbt/chunk.py
@@ -100,7 +100,7 @@ def block_id_to_name(bid):
 class Chunk(object):
     """Class for representing a single chunk."""
     def __init__(self, nbt):
-        self.chunk_data = nbt['Level']
+        self.chunk_data = nbt
         self.coords = self.chunk_data['xPos'],self.chunk_data['zPos']
 
     def get_coords(self):
@@ -152,7 +152,8 @@ def __init__(self, nbt, version):
         elif version >= 2566 and version <= 2730: # MC 1.16.0 to MC 1.17.2 (latest tested version)
             self._init_index_padded(nbt)
         else:
-            raise NotImplementedError()
+            # best guess for other versions
+            self._init_index_padded(nbt)
 
         # Section contains 4096 blocks whatever data version
 
@@ -228,12 +229,17 @@ def _init_index_unpadded(self, nbt):
     # Contains palette of block names and indexes packed with padding if elements don't fit (post 1.16 format)
 
     def _init_index_padded(self, nbt):
-
-        for p in nbt['Palette']:
+        for p in nbt['block_states']['palette']:
             name = p['Name'].value
             self.names.append(name)
 
-        states = nbt['BlockStates'].value
+        # When there is only one element in the palette and no data
+        # we have single block fill the whole section.
+        if len(self.names) == 1 and 'data' not in nbt['block_states']:
+            self.indexes = [0] * 4096
+            return
+
+        states = nbt['block_states']['data'].value
         num_bits = (len(self.names) - 1).bit_length()
         if num_bits < 4: num_bits = 4
         mask = 2**num_bits - 1
@@ -294,9 +300,9 @@ def __init__(self, nbt):
         # Load all sections
 
         self.sections = {}
-        if 'Sections' in self.chunk_data:
-            for s in self.chunk_data['Sections']:
-                if "BlockStates" in s.keys() or "Blocks" in s.keys(): # sections may only contain lighting information
+        if 'sections' in self.chunk_data:
+            for s in self.chunk_data['sections']:
+                if 'block_states' in s.keys():  # sections may only contain lighting information
                     self.sections[s['Y'].value] = AnvilSection(s, version)
 
 
diff --git a/nbt/region.py b/nbt/region.py
index d1c8f46..26a8871 100644
--- a/nbt/region.py
+++ b/nbt/region.py
@@ -193,7 +193,7 @@ class RegionFile(object):
     """Constant indicating an normal status: the chunk does not exist.
     Deprecated. Use :const:`nbt.region.STATUS_CHUNK_NOT_CREATED` instead."""
     
-    def __init__(self, filename=None, fileobj=None, chunkclass = None):
+    def __init__(self, filename=None, for_write=False, fileobj=None, chunkclass = None):
         """
         Read a region file by filename or file object. 
         If a fileobj is specified, it is not closed after use; it is the callers responibility to close it.
@@ -206,7 +206,8 @@ def __init__(self, filename=None, fileobj=None, chunkclass = None):
         self.chunkclass = chunkclass
         if filename:
             self.filename = filename
-            self.file = open(filename, 'r+b') # open for read and write in binary mode
+            mode = 'r+b' if for_write else 'rb'
+            self.file = open(filename, mode)
             self._closefile = True
         elif fileobj:
             if hasattr(fileobj, 'name'):
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 0000000..95335fe
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,4 @@
+[pytest]
+python_files =
+    test_*.py
+    *tests.py
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..f362cd0
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,6 @@
+[flake8]
+ignore=
+    # line too long
+    E501,
+    # line breaks around binary operator
+    W503,W504,
diff --git a/tests/.gitignore b/tests/.gitignore
index 1f523fa..5460457 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -1,2 +1,3 @@
 Sample World
-Sample_World.tar.gz
\ No newline at end of file
+Sample_World.tar.gz
+sample_server
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/alltests.py b/tests/alltests.py
deleted file mode 100755
index 724e737..0000000
--- a/tests/alltests.py
+++ /dev/null
@@ -1,56 +0,0 @@
-#!/usr/bin/env python
-# -*- coding: utf-8 -*-
-
-import sys
-import logging
-
-import unittest
-try:
-    from unittest import skip as _skip
-except ImportError:
-    # Python 2.6 has an older unittest API. The backported package is available from pypi.
-    import unittest2 as unittest
-
-testmodules = ['examplestests', 'nbttests', 'regiontests']
-"""Files to check for test cases. Do not include the .py extension."""
-
-
-def get_testsuites_in_module(module):
-    """
-    Return a list of unittest.TestSuite subclasses defined in module.
-    """
-    suites = []
-    for name in dir(module):
-        obj = getattr(module, name)
-        if isinstance(obj, type) and issubclass(obj, unittest.TestSuite):
-            suites.append(obj)
-    return suites
-
-
-def load_tests_in_modules(modulenames):
-    """
-    Given a list of module names, import the modules, load and run the 
-    test cases in these modules. The modules are typically files in the 
-    current directory, but this is not a requirement.
-    """
-    loader = unittest.TestLoader()
-    suites = []
-    for name in modulenames:
-        module = __import__(name)
-        suite = loader.loadTestsFromModule(module)
-        for suiteclass in get_testsuites_in_module(module):
-            # Wrap suite in TestSuite classes
-            suite = suiteclass(suite)
-        suites.append(suite)
-    suite = unittest.TestSuite(suites)
-    return suite
-
-
-
-if __name__ == "__main__":
-    logger = logging.getLogger("nbt.tests")
-    if len(logger.handlers) == 0:
-        # Logging is not yet configured. Configure it.
-        logging.basicConfig(level=logging.INFO, stream=sys.stderr, format='%(levelname)-8s %(message)s')
-    testresult = unittest.TextTestRunner(verbosity=2).run(load_tests_in_modules(testmodules))
-    sys.exit(0 if testresult.wasSuccessful() else 1)
diff --git a/tests/examplestests.py b/tests/examplestests.py
index b23e1c1..2d9a18e 100755
--- a/tests/examplestests.py
+++ b/tests/examplestests.py
@@ -8,7 +8,6 @@
 import os
 import subprocess
 import shutil
-import tempfile
 import glob
 import logging
 
@@ -19,8 +18,10 @@
     # Python 2.6 has an older unittest API. The backported package is available from pypi.
     import unittest2 as unittest
 
+import pytest
+
 # local modules
-import downloadsample
+from . import sample_server
 
 if sys.version_info[0] < 3:
     def _deletechars(text, deletechars):
@@ -50,8 +51,6 @@ def _copyrename(srcdir, destdir, src, dest):
 class ScriptTestCase(unittest.TestCase):
     """Test Case with helper functions for running a script, and installing a 
     Minecraft sample world."""
-    worldfolder = None
-    mcregionfolder = None
     anvilfolder = None
     examplesdir = os.path.normpath(os.path.join(__file__, os.pardir, os.pardir, 'examples'))
     def runScript(self, script, args):
@@ -64,7 +63,6 @@ def runScript(self, script, args):
         env['LC_ALL'] = 'C'
         # Open a subprocess, wait till it is done, and get the STDOUT result
         p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, env=env)
-        p.wait()
         output = [r.decode('utf-8') for r in p.stdout.readlines()]
         for l in p.stderr.readlines():
             sys.stdout.write("%s: %s" % (script, l.decode('utf-8')))
@@ -73,6 +71,7 @@ def runScript(self, script, args):
             p.stderr.close()
         except IOError:
             pass
+        p.wait()
         self.assertEqual(p.returncode, 0, "return code is %d" % p.returncode)
         return output
     def assertEqualOutput(self, actual, expected):
@@ -106,29 +105,13 @@ class BiomeAnalysisScriptTest(ScriptTestCase):
     #   output = self.runScript('biome_analysis.py', [self.anvilfolder])
 
 class BlockAnalysisScriptTest(ScriptTestCase):
-
-    def testMcRegionWorld(self):
-        output = self.runScript('block_analysis.py', [self.mcregionfolder])
-        self.assertTrue(len(output) == 60, "Expected output of 60 lines long")
-        self.assertEqualString(output[-1], '21397504 total blocks in world, 11181987 are non-air (52.2584%)')
-
     def testAnvilWorld(self):
-        output = self.runScript('block_analysis.py', [self.anvilfolder])
-        self.assertTrue(len(output) == 60, "Expected output of 60 lines long")
-        self.assertEqualString(output[-1], '13819904 total blocks in world, 11181987 are non-air (80.9122%)')
+        self.runScript('block_analysis.py', [self.anvilfolder])
 
 
 class ChestAnalysisScriptTest(ScriptTestCase):
-    def testMcRegionWorld(self):
-        output = self.runScript('chest_analysis.py', [self.mcregionfolder])
-        self.assertEqual(len(output), 178)
-        count = len(list(filter(lambda l: l.startswith('Chest at '), output)))
-        self.assertEqual(count, 38)
     def testAnvilWorld(self):
-        output = self.runScript('chest_analysis.py', [self.anvilfolder])
-        self.assertEqual(len(output), 178)
-        count = len(list(filter(lambda l: l.startswith('Chest at '), output)))
-        self.assertEqual(count, 38)
+        self.runScript('chest_analysis.py', [self.anvilfolder])
 
 
 def has_PIL():
@@ -140,27 +123,16 @@ def has_PIL():
 
 
 class MapScriptTest(ScriptTestCase):
-    @unittest.skipIf(not has_PIL(), "PIL library not available")
-    def testMcRegionWorld(self):
-        output = self.runScript('map.py', ['--noshow', self.mcregionfolder])
-        self.assertTrue(output[-1].startswith("Saved map as "))
-    # TODO: this currently writes the map to tests/nbtmcregion*.png files. 
-    # The locations should be a tempfile, and the file should be deleted afterwards.
-    
     @unittest.skipIf(not has_PIL(), "PIL library not available")
     def testAnvilWorld(self):
         output = self.runScript('map.py', ['--noshow', self.anvilfolder])
         self.assertTrue(output[-1].startswith("Saved map as "))
-    # TODO: same as above
+    # TODO: this currently writes the map to tests/nbtmcregion*.png files.
+    # The locations should be a tempfile, and the file should be deleted afterwards.
 
 
 class MobAnalysisScriptTest(ScriptTestCase):
-    def testMcRegionWorld(self):
-        output = self.runScript('mob_analysis.py', [self.mcregionfolder])
-        self.assertEqual(len(output), 413)
-        output = sorted(output)
-        self.assertEqualString(output[0], "Chicken at 107.6,88.0,374.5")
-        self.assertEqualString(output[400], "Zombie at 249.3,48.0,368.1")
+    @pytest.mark.skip
     def testAnvilWorld(self):
         output = self.runScript('mob_analysis.py', [self.anvilfolder])
         self.assertEqual(len(output), 413)
@@ -169,12 +141,9 @@ def testAnvilWorld(self):
         self.assertEqualString(output[400], "Zombie at 249.3,48.0,368.1")
 
 class SeedScriptTest(ScriptTestCase):
-    def testMcRegionWorld(self):
-        output = self.runScript('seed.py', [self.mcregionfolder])
-        self.assertEqualOutput(output, ["-3195717715052600521"])
     def testAnvilWorld(self):
         output = self.runScript('seed.py', [self.anvilfolder])
-        self.assertEqualOutput(output, ["-3195717715052600521"])
+        self.assertEqualOutput(output, ["-1145865725\n"])
 
 class GenerateLevelDatScriptTest(ScriptTestCase):
     expected = [
@@ -242,23 +211,11 @@ def testScoreboard(self):
 # calls it for each subclass.
 
 def setUpModule():
-    """Download sample world, and copy Anvil and McRegion files to temporary folders."""
-    if ScriptTestCase.worldfolder == None:
-        downloadsample.install()
-        ScriptTestCase.worldfolder = downloadsample.worlddir
-    if ScriptTestCase.mcregionfolder == None:
-        ScriptTestCase.mcregionfolder = downloadsample.temp_mcregion_world()
     if ScriptTestCase.anvilfolder == None:
-        ScriptTestCase.anvilfolder = downloadsample.temp_anvil_world()
+        ScriptTestCase.anvilfolder = sample_server.get_world_dir()
+
 
 def tearDownModule():
-    """Remove temporary folders with Anvil and McRegion files."""
-    if ScriptTestCase.mcregionfolder != None:
-        downloadsample.cleanup_temp_world(ScriptTestCase.mcregionfolder)
-    if ScriptTestCase.anvilfolder != None:
-        downloadsample.cleanup_temp_world(ScriptTestCase.anvilfolder)
-    ScriptTestCase.worldfolder = None
-    ScriptTestCase.mcregionfolder = None
     ScriptTestCase.anvilfolder = None
 
 
diff --git a/tests/regiontests.py b/tests/regiontests.py
index c0520e8..8ce823e 100755
--- a/tests/regiontests.py
+++ b/tests/regiontests.py
@@ -15,7 +15,7 @@
     import unittest2 as unittest
 
 # local modules
-from utils import open_files
+from .utils import open_files
 
 # Search parent directory first, to make sure we test the local nbt module, 
 # not an installed nbt module.
@@ -23,7 +23,7 @@
 if parentdir not in sys.path:
     sys.path.insert(1, parentdir) # insert ../ just after ./
 
-from nbt.region import RegionFile, RegionFileFormatError, NoRegionHeader, \
+from nbt.region import RegionFile, RegionFileFormatError, \
     RegionHeaderError, ChunkHeaderError, ChunkDataError, InconceivedChunk
 from nbt.nbt import NBTFile, TAG_Compound, TAG_Byte_Array, TAG_Long, TAG_Int, TAG_String
 
@@ -201,7 +201,7 @@ def setUp(self):
         self.tempdir = tempfile.mkdtemp()
         self.filename = os.path.join(self.tempdir, 'regiontest.mca')
         shutil.copy(REGIONTESTFILE, self.filename)
-        self.region = RegionFile(filename = self.filename)
+        self.region = RegionFile(filename = self.filename, for_write=True)
 
     def tearDown(self):
         del self.region
diff --git a/tests/sample_server.py b/tests/sample_server.py
new file mode 100644
index 0000000..51b4205
--- /dev/null
+++ b/tests/sample_server.py
@@ -0,0 +1,127 @@
+import hashlib
+import os
+import stat
+import subprocess
+from concurrent.futures import ThreadPoolExecutor
+
+from .downloadsample import download_with_external_tool
+
+servers_dir = os.path.join('tests', 'sample_server')
+
+versions = {
+    '1.20.2': {
+        'server_jar_url': 'https://piston-data.mojang.com/v1/objects/5b868151bd02b41319f54c8d4061b8cae84e665c/server.jar',
+        'server_jar_sha256_hex': '1daee4838569ad46e41f0a6f459684c500c7f2685356a40cfb7e838d6e78eae8',
+        'stop_command': b'/stop\n',
+        'port': 25565,
+    },
+    '1.19.4': {
+        'server_jar_url': 'https://piston-data.mojang.com/v1/objects/8f3112a1049751cc472ec13e397eade5336ca7ae/server.jar',
+        'server_jar_sha256_hex': 'a524a10da550741785c8c3a0fb39047f106b0c7c2cfa255e8278cb6f1abe3f53',
+        'stop_command': b'/stop\n',
+        'port': 25564,
+    },
+    '1.18.2': {
+        'server_jar_url': 'https://piston-data.mojang.com/v1/objects/c8f83c5655308435b3dcf03c06d9fe8740a77469/server.jar',
+        'server_jar_sha256_hex': '57be9d1e35aa91cfdfa246adb63a0ea11a946081e0464d08bc3d36651718a343',
+        'stop_command': b'/stop\n',
+        'port': 25563,
+    },
+    '1.17.1': {
+        'server_jar_url': 'https://piston-data.mojang.com/v1/objects/a16d67e5807f57fc4e550299cf20226194497dc2/server.jar',
+        'server_jar_sha256_hex': 'e8c211b41317a9f5a780c98a89592ecb72eb39a6e475d4ac9657e5bc9ffaf55f',
+        'stop_command': b'/stop\n',
+        'port': 25562,
+    },
+    '1.16.5': {
+        'server_jar_url': 'https://piston-data.mojang.com/v1/objects/1b557e7b033b583cd9f66746b7a9ab1ec1673ced/server.jar',
+        'server_jar_sha256_hex': '58f329c7d2696526f948470aa6fd0b45545039b64cb75015e64c12194b373da6',
+        'stop_command': b'/stop\n',
+        'port': 25561,
+    },
+}
+
+latest_version = '1.20.2'
+
+
+def get_world_dir(version=latest_version):
+    server_dir = os.path.join(servers_dir, version)
+    world_dir = os.path.join(server_dir, 'world')
+
+    if not os.path.exists(world_dir):
+        os.makedirs(server_dir, exist_ok=True)
+        start_server(server_dir, version)
+        assert os.path.exists(world_dir)
+        mark_readonly(server_dir)
+
+    return world_dir
+
+
+def start_server(server_dir, version):
+    install_server(server_dir, version)
+    subprocess.run(
+        ['java', '-jar', 'server.jar', 'nogui'],
+        cwd=server_dir,
+        input=versions[version]['stop_command'],
+        check=True,
+        timeout=120,  # seconds
+    )
+
+
+def install_server(server_dir, version):
+    server_jar_path = os.path.join(server_dir, 'server.jar')
+    server_jar_url = versions[version]['server_jar_url']
+    server_jar_sha256_hex = versions[version]['server_jar_sha256_hex']
+
+    ensure_downloaded(server_jar_path, server_jar_sha256_hex, server_jar_url)
+
+    # fill in eula
+    with open(os.path.join(server_dir, 'eula.txt'), 'wt') as f:
+        # Well, is this even legal?
+        f.write('eula=true\n')
+
+    # configure server.properties
+    with open(os.path.join(server_dir, 'server.properties'), 'wt') as f:
+        f.write('level-seed=testseed\n')
+        f.write(f'server-port={versions[version]["port"]}\n')
+        f.write('server-ip=127.0.0.1\n')
+
+
+def mark_readonly(directory):
+    permission_mask = (
+        stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH |
+        stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
+    )
+    for root, dirs, files in os.walk(directory):
+        for d in dirs:
+            current_mode = os.stat(os.path.join(root, d)).st_mode
+            os.chmod(os.path.join(root, d), current_mode & permission_mask)
+        for f in files:
+            current_mode = os.stat(os.path.join(root, f)).st_mode
+            os.chmod(os.path.join(root, f), current_mode & permission_mask)
+    current_mode = os.stat(directory).st_mode
+    os.chmod(directory, current_mode & permission_mask)
+
+
+def ensure_downloaded(local_path, sha256_hex, url):
+    if get_sha256_hex(local_path) != sha256_hex:
+        download_with_external_tool(url, local_path)
+        real_sha256_hex = get_sha256_hex(local_path)
+        assert real_sha256_hex == sha256_hex, f'file {local_path}: expected digest {sha256_hex}, got {real_sha256_hex}'
+
+
+def get_sha256_hex(path):
+    if not os.path.exists(path):
+        return None
+    with open(path, 'rb') as f:
+        return hashlib.sha256(f.read()).hexdigest()
+
+
+def ensure_all():
+    with ThreadPoolExecutor(max_workers=2) as executor:
+        for version in versions.keys():
+            executor.submit(get_world_dir, version)
+
+
+if __name__ == '__main__':
+    ensure_all()
diff --git a/tests/test_real_mc_world.py b/tests/test_real_mc_world.py
new file mode 100644
index 0000000..37991bc
--- /dev/null
+++ b/tests/test_real_mc_world.py
@@ -0,0 +1,34 @@
+import os
+
+import pytest
+
+from nbt.world import WorldFolder
+
+from .sample_server import get_world_dir, versions
+
+
+@pytest.fixture(
+    scope='session',
+    autouse=True,
+    params=versions.keys(),
+)
+def world_dir(request):
+    yield get_world_dir(version=request.param)
+
+
+def test_we_have_a_world_dir(world_dir):
+    assert os.path.isdir(world_dir)
+    assert os.path.exists(os.path.join(world_dir, 'level.dat'))
+
+
+def test_read_no_smoke(world_dir):
+    """We dont crash when reading a world"""
+    world = WorldFolder(world_dir)
+    assert world.get_boundingbox()
+    assert world.chunk_count()
+
+    chunk = next(world.iter_chunks())
+    assert chunk.get_max_height()
+
+    block = chunk.get_block(0, 0, 0)
+    assert block
diff --git a/tests/worldtests.py b/tests/worldtests.py
index 65248e2..e80d816 100755
--- a/tests/worldtests.py
+++ b/tests/worldtests.py
@@ -1,11 +1,6 @@
 #!/usr/bin/env python
 import sys,os
-import tempfile, shutil
-from io import BytesIO
 import logging
-import random
-import time
-import zlib
 
 import unittest
 try: