tests: simplify timestamp mocking

$SOURCE_DATE_EPOCH is now the officially supported mechanism for
guaranteeing stable output timestamps, which means we can simply run the
tests using that, and drop some code.

This also fixes asciidoc-py#131 since the variable would override the mocked time,
resulting in tests failing if $SOURCE_DATE_EPOCH was set in the
environment (e.g. for linux distro packaging).

tests/testasciidoc.py

@@ -68,28 +68,6 @@ def normalize_data(lines):
     return result
 
 
-def mock_localtime(f, _localtime=time.localtime):
-    """Mock time module to generate stable output."""
-    _frozentime = 0X3DE170D6
-    _frozentz = 'UTC+00'
-
-    def _frozen_localtime(t=_frozentime + 1):
-        assert t > _frozentime, 'File created before first public release'
-        return _localtime(_frozentime)
-
-    def generate_expected(self, backend):
-        time.localtime = _frozen_localtime
-        os.environ['TZ'] = _frozentz
-        time.tzset()
-        try:
-            return f(self, backend)
-        finally:
-            time.localtime = _localtime
-            del os.environ['TZ']
-            time.tzset()
-    return generate_expected
-
-
 class AsciiDocTest(object):
     def __init__(self):
         self.number = None      # Test number (1..).
@@ -188,7 +166,6 @@ def get_expected(self, backend):
             result = [s.rstrip() for s in result]
         return result
 
-    @mock_localtime
     def generate_expected(self, backend):
         """
         Generate and return test data output for backend.
@@ -386,6 +363,8 @@ def read_until(self, regexp):
 
 
 if __name__ == '__main__':
+    # guarantee a stable timestamp matching the test fixtures
+    os.environ['SOURCE_DATE_EPOCH'] = '1038184662'
     # Process command line options.
     from argparse import ArgumentParser
     parser = ArgumentParser(description='Run AsciiDoc conformance tests specified in '