Add rustdoc GUI test

Author: GuillaumeGomez

src/test/rustdoc-gui/where-whitespace.goml

@@ -0,0 +1,27 @@
+// This test ensures that the where conditions are correctly displayed.
+goto: file://|DOC_PATH|/lib2/trait.Whitespace.html
+show-text: true
+// First, we check in the trait definition if the where clause is "on its own" (not on the same
+// line than "pub trait Whitespace<Idx>").
+compare-elements-position-false: (".item-decl code", ".where.fmt-newline", ("y"))
+// And that the code following it isn't on the same line either.
+compare-elements-position-false: (".item-decl .fnname", ".where.fmt-newline", ("y"))
+
+goto: file://|DOC_PATH|/lib2/struct.WhereWhitespace.html
+// We make the screen a bit wider to ensure that the trait impl is on one line.
+size: (915, 915)
+
+compare-elements-position-false: ("#method\.new .fnname", "#method\.new .where.fmt-newline", ("y"))
+// We ensure that both the trait name and the struct name are on the same line in
+// "impl<K, T> Whitespace<&K> for WhereWhitespace<T>".
+compare-elements-position: (
+    "#trait-implementations-list .impl h3 .trait",
+    "#trait-implementations-list .impl h3 .struct",
+    ("y"),
+)
+// And we now check that the where condition isn't on the same line.
+compare-elements-position-false: (
+    "#trait-implementations-list .impl h3 .trait",
+    "#trait-implementations-list .impl h3 .where.fmt-newline",
+    ("y"),
+)