Add some regression testing code.

This should help detect if any code changes introduce unexpected
behavior.

run_regression_test.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python
+
+import tempfile
+import sys
+import subprocess
+import shutil
+import os
+import mclevel
+import hashlib
+import contextlib
+import gzip
+import fnmatch
+import tarfile
+import zipfile
+
+def generate_file_list(directory):
+    for dirpath, dirnames, filenames in os.walk(directory):
+        for filename in filenames:
+            yield os.path.join(dirpath, filename)
+
+def sha1_file(name, checksum=None):
+    CHUNKSIZE=1024
+    if checksum is None:
+        checksum = hashlib.sha1()
+    if fnmatch.fnmatch(name, "*.dat"):
+        opener = gzip.open
+    else:
+        opener = open
+
+    with contextlib.closing(opener(name, 'rb')) as data:
+        chunk = data.read(CHUNKSIZE)
+        while len(chunk) == CHUNKSIZE:
+            checksum.update(chunk)
+            chunk = data.read(CHUNKSIZE)
+        else:
+            checksum.update(chunk)
+    return checksum
+
+def calculate_result(directory):
+    checksum = hashlib.sha1()
+    for filename in sorted(generate_file_list(directory)):
+        sha1_file(filename, checksum)
+    return checksum.hexdigest()
+
+@contextlib.contextmanager
+def temporary_directory(prefix='regr'):
+    name = tempfile.mkdtemp(prefix)
+    try:
+        yield name
+    finally:
+        shutil.rmtree(name)
+
+@contextlib.contextmanager
+def directory_clone(src):
+    with temporary_directory('regr') as name:
+        subdir = os.path.join(name, "subdir")
+        shutil.copytree(src, subdir)
+        yield subdir
+
+@contextlib.contextmanager
+def unzipped_content(src):
+    with temporary_directory() as dest:
+        f = zipfile.ZipFile.open(name)
+        f.extractall(dest)
+        yield dest
+
+@contextlib.contextmanager
+def untared_content(src):
+    with temporary_directory() as dest:
+        f = tarfile.TarFile.open(src)
+        f.extractall(dest)
+        yield dest
+
+class RegressionError(Exception): pass
+
+def do_test(test_data, result_check, arguments=[]):
+    """Run a regression test on the given world.
+
+    result_check - sha1 of the recursive tree generated
+    arguments - arguments to give to mce.py on execution
+    """
+    result_check = result_check.lower()
+
+    env = {
+            'MCE_RANDOM_SEED' : '42',
+            'MCE_LAST_PLAYED' : '42'
+    }
+
+    with directory_clone(test_data) as directory:
+        proc = subprocess.Popen([
+            "./mce.py",
+            directory] + arguments, stdin=subprocess.PIPE, stderr=subprocess.STDOUT, env=env)
+        proc.stdin.close()
+        result = proc.wait()
+
+        if os.WIFEXITED(result) and os.WEXITSTATUS(result):
+            raise RegressionError("Program execution failed!")
+
+        checksum = calculate_result(directory).lower()
+        if checksum != result_check.lower():
+            raise RegressionError("Checksum mismatch: {0!r} != {1!r}".format(checksum, result_check))
+    print "[OK]"
+
+
+def main(argv):
+    with untared_content("regression_test/alpha.tar.gz") as directory:
+        test_data = os.path.join(directory, "alpha")
+        do_test(test_data, 'ca66277d8037fde5aea3a135dd186f91e4bf4bef')
+        do_test(test_data, '0f4cbb81f7f109cee10606b82f27fb2681a22f50', ['degrief'])
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv))
+