Add functional test to parse all Fedora spec files

Signed-off-by: Nikola Forró <nforro@redhat.com>

plans/functional.fmf

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+summary:
+  Functional tests
+discover+:
+  filter: tier:2
+prepare:
+  - how: install
+    package: xz
+  - how: shell
+    script: |
+      curl -O https://src.fedoraproject.org/lookaside/rpm-specs-latest.tar.xz
+      tar -xf rpm-specs-latest.tar.xz -C /tmp

tests/functional.fmf

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+summary:
+  Functional tests
+require:
+  - python3-pytest
+  - python3-specfile
+  - redhat-rpm-config
+  - rpmautospec-rpm-macros
+  - MUMPS-srpm-macros
+  - ansible-srpm-macros
+  - blis-srpm-macros
+  - efi-srpm-macros
+  - folly-srpm-macros
+  - fonts-srpm-macros
+  - fpc-srpm-macros
+  - ghc-srpm-macros
+  - gnat-srpm-macros
+  - go-srpm-macros
+  - kernel-srpm-macros
+  - lua-srpm-macros
+  - nbdkit-srpm-macros
+  - ocaml-srpm-macros
+  - openblas-srpm-macros
+  - package-notes-srpm-macros
+  - perl-srpm-macros
+  - pyproject-srpm-macros
+  - python-srpm-macros
+  - qt5-srpm-macros
+  - qt6-srpm-macros
+  - rust-srpm-macros
+  - typelib-srpm-macros
+tag:
+  - functional
+tier: 2
+duration: 1h
+# running from the "tests" directory prevents pytest from processing "tests/functional/conftest.py"
+path: /
+test: python3 -m pytest --verbose --specdir=/tmp/rpm-specs tests/functional

tests/functional/__init__.py

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+# Copyright Contributors to the Packit project.
+# SPDX-License-Identifier: MIT

tests/functional/conftest.py

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+# Copyright Contributors to the Packit project.
+# SPDX-License-Identifier: MIT
+
+from pathlib import Path
+
+
+def pytest_addoption(parser):
+    parser.addoption(
+        "--specdir",
+        action="store",
+        default=None,
+        help="path to a directory containing spec files",
+    )
+
+
+def pytest_generate_tests(metafunc):
+    if "spec_path" in metafunc.fixturenames:
+        specdir = metafunc.config.getoption("specdir")
+        specs = list(Path(specdir).glob("*.spec")) if specdir else []
+        metafunc.parametrize("spec_path", specs, ids=lambda p: p.name)

tests/functional/test_parse.py

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+# Copyright Contributors to the Packit project.
+# SPDX-License-Identifier: MIT
+
+from specfile import Specfile
+
+
+def test_parse(spec_path):
+    spec = Specfile(spec_path, force_parse=True)
+    assert spec.expanded_version