test: add read/write tests for util.toml

Add two unit tests for our toml util module.
- Write an object with util.toml, read it with util.toml, and compare
  written and read objects.
- Write an object directly as a string, read it with util.toml,
  comparing with an expected object.

A test that writes with util.toml, reads as string, and verifies the
read string is difficult to do in a general way, because each toml
module we support writes files in a slightly different way.

test/mod/test_util_toml.py

@@ -0,0 +1,43 @@
+#
+# Tests for the 'osbuild.util.toml' module
+#
+import os
+from tempfile import TemporaryDirectory
+
+from osbuild.util import toml
+
+data_obj = {
+    "top": {
+        "t2-1": {
+            "list": ["a", "b", "c"]
+        },
+        "t2-2": {
+            "str": "test"
+        }
+    }
+}
+
+data_str = """
+[top.t2-1]
+list = ["a", "b", "c"]
+
+[top.t2-2]
+str = "test"
+"""
+
+
+def test_write_read():
+    with TemporaryDirectory() as tmpdir:
+        path = os.path.join(tmpdir, "test.toml")
+        toml.dump_to_file(data_obj, path)
+        rdata = toml.load_from_file(path)
+        assert data_obj == rdata
+
+
+def test_read():
+    with TemporaryDirectory() as tmpdir:
+        path = os.path.join(tmpdir, "test.toml")
+        with open(path, "w", encoding="utf-8") as test_file:
+            test_file.write(data_str)
+        rdata = toml.load_from_file(path)
+        assert rdata == data_obj