Add TMT test for upstream ticket 534

Signed-off-by: Ondrej Mosnáček <omosnacek@gmail.com>

.fmf/version

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+1

plans/ci.fmf

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+summary: Run CI tests
+discover:
+    how: fmf
+execute:
+    how: tmt
+

tests/main.fmf

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+component: python-ruamel-yaml

tests/sf534/main.fmf

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+summary: Regression test for upstream ticket 534
+require: python3-ruamel-yaml
+link:
+  - verifies: https://sourceforge.net/p/ruamel-yaml/tickets/534/
+test: python3 test.py

tests/sf534/test.py

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+# Taken from https://sourceforge.net/p/ruamel-yaml/tickets/534/
+
+from io import StringIO
+from ruamel.yaml import YAML
+
+original = '0: foo\n'
+py_original = {0: 'foo'}
+prefix = '%YAML 1.1\n---\n'
+
+yaml = YAML()
+yaml.version = (1, 1)
+
+loaded = yaml.load(original)
+assert loaded == py_original
+
+print('Fresh')
+stream = StringIO()
+yaml.dump(py_original, stream)
+fresh = stream.getvalue()
+print(fresh)
+assert fresh.startswith(prefix)
+trimmed = fresh[len(prefix):]
+assert trimmed == original, f"{trimmed!r} != {original!r}"
+
+print('Round trip')
+stream = StringIO()
+yaml.dump(loaded, stream)
+round_tripped = stream.getvalue()
+print(round_tripped)
+assert round_tripped.startswith(prefix)
+trimmed = round_tripped[len(prefix):]
+assert trimmed == original, f"{trimmed!r} != {original!r}"