Add roundtrip parsing tests for basic_shape/position

tests/unit/style/parsing/mod.rs

@@ -0,0 +1,29 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Tests for parsing and serialization of values/properties
+
+use cssparser::Parser;
+
+fn parse<T, F: Fn(&mut Parser) -> Result<T, ()>>(f: F, s: &str) -> Result<T, ()> {
+    let mut parser = Parser::new(s);
+    f(&mut parser)
+}
+
+// This is a macro so that the file/line information
+// is preserved in the panic
+macro_rules! assert_roundtrip {
+    ($fun:expr, $input:expr, $output:expr) => {
+        let parsed = $crate::parsing::parse($fun, $input)
+                        .expect(&format!("Failed to parse {}", $input));
+        let mut serialized = String::new();
+        ::cssparser::ToCss::to_css(&parsed, &mut serialized)
+                        .expect("Failed to serialize");
+        assert_eq!(serialized, $output);
+    }
+}
+
+
+mod basic_shape;
+mod position;