test: check nested selector groupings and partial overlap cases

Author: ChristianMurphy

Diff for: test/duplicated-extension.js

@@ -55,3 +55,10 @@ test(
     '.one.two {} .two{&.one {}}',
     '.one.two {}'
 );
+
+test(
+    'nested selector grouping',
+    [nestedCSS, scss],
+    '.one {&.two, .two& {}} .one {.two&, &.two {}}',
+    '.one.two, .two.one {}'
+);

Diff for: test/unique-css.js

@@ -163,3 +163,10 @@ test(
     '@keyframes a {0% {} 100% {}} @-webkit-keyframes a {0% {} 100% {}}',
     '@keyframes a {0% {} 100% {}} @-webkit-keyframes a {0% {} 100% {}}'
 );
+
+test(
+    'selector groups partially overlapping',
+    css,
+    '.one, .two {} .one, .two, .three {}',
+    '.one, .two {} .one, .two, .three {}'
+);