added tests for trailing commas and css imports

tests/imports.rs

@@ -105,6 +105,38 @@ fn comma_separated_import_order() {
     );
 }
 
+#[test]
+fn comma_separated_import_order_css() {
+    let input =
+        "@import 'comma_separated_import_order1.css', 'comma_separated_import_order2', url(third);";
+    tempfile!("comma_separated_import_order1.css", "p { color: red; }");
+    tempfile!("comma_separated_import_order2", "p { color: blue; }");
+    assert_eq!(
+        "@import \"comma_separated_import_order1.css\";\n\np {\n  color: blue;\n}\n@import url(third);\n",
+        &grass::from_string(input.to_string(), &grass::Options::default()).expect(input)
+    );
+}
+
+#[test]
+fn comma_separated_import_trailing() {
+    let input =
+        "@import 'comma_separated_import_trailing1', 'comma_separated_import_trailing2', url(third),,,,,,,,;";
+    tempfile!("comma_separated_import_trailing1", "p { color: red; }");
+    tempfile!("comma_separated_import_trailing2", "p { color: blue; }");
+
+    match grass::from_string(input.to_string(), &grass::Options::default()) {
+        Ok(..) => panic!("did not fail"),
+        Err(e) => assert_eq!(
+            "Error: Expected expression.",
+            e.to_string()
+                .chars()
+                .take_while(|c| *c != '\n')
+                .collect::<String>()
+                .as_str()
+        ),
+    }
+}
+
 #[test]
 fn finds_name_scss() {
     let input = "@import \"finds_name_scss\";\na {\n color: $a;\n}";