pytests: add some tests for the cfg_builder

This uses pytest not unittest, unittest is such a pain in the ass and
pytest is so much nicer..

Author: dcbaker

pytests/cfg_builder_tests.py

@@ -0,0 +1,30 @@
+# SPDX-license-identifier: Apache-2.0
+# Copyright © 2021 Intel Corporation
+
+from pathlib import Path
+
+from mesonbuild import mparser
+from mesonbuild.cargo.cfg_builder import *
+from mesonbuild.cargo.cfg_parser import *
+from mesonbuild.cargo.nodebuilder import NodeBuilder
+
+
+class TestCfgBuilder:
+
+    def test_eq(self) -> None:
+        builder = NodeBuilder(Path(''))
+
+        id = builder.id('host_machine')
+        left = mparser.MethodNode('', 0, 0, id, 'system', mparser.ArgumentNode(builder._builder.token()))
+        right = builder.string('sunos')
+        expected = mparser.ComparisonNode('==', left, right)
+
+        # use illumos to test the translation from cargo names to meson names
+        ast = parse('cfg(target_os = "illumos")')
+        builder = NodeBuilder(Path(''))
+        build(builder, ast)
+        final = builder.finalize()
+        assert len(final.lines) == 1
+
+        actual = final.lines[0]
+        assert actual == expected