Add a functional test for BuildFile.write()

tests/functional/test_dependency_files.py

@@ -0,0 +1,26 @@
+from packaging.version import Version as PypiVer
+from semantic_version import Version as SemVer
+
+import pytest
+
+from antsibull.dependency_files import BuildFile
+
+
+SIMPLE_TEST_FILE = """_ansible_version: 4
+_ansible_base_version: 2.11.0rc1
+community.general: >=1.0.0,<2.0.0
+community.routeros: >=2.0.0-a2,<3.0.0
+"""
+
+SIMPLE_TEST_DEPS = {'community.general': SemVer('1.0.0'),
+                    'community.routeros': SemVer('2.0.0-a2'),
+                    }
+
+@pytest.mark.parametrize('dependencies, file_contents', ((SIMPLE_TEST_DEPS, SIMPLE_TEST_FILE),))
+def test_build_file_write(tmpdir, dependencies, file_contents):
+    filename = tmpdir / 'test.build'
+    bf = BuildFile(filename)
+    bf.write(PypiVer('4.0.0'), '2.11.0rc1', dependencies)
+
+    with open(filename) as f:
+        assert f.read() == file_contents