vim: Fix edge-case in } when trailing newline is absent

Added .assert_shared_state() to NeovimBackedTestContext – although it's
not strictly necessary to show the expected behaviour in the test file
(as we can just compare to neovim's JSON recording), it makes it much
easier to understand what we're testing.

crates/editor/src/test/editor_test_context.rs

@@ -210,6 +210,10 @@ impl<'a> EditorTestContext<'a> {
         self.assert_selections(expected_selections, marked_text.to_string())
     }
 
+    pub fn editor_state(&mut self) -> String {
+        generate_marked_text(self.buffer_text().as_str(), &self.editor_selections(), true)
+    }
+
     #[track_caller]
     pub fn assert_editor_background_highlights<Tag: 'static>(&mut self, marked_text: &str) {
         let expected_ranges = self.ranges(marked_text);
@@ -248,14 +252,8 @@ impl<'a> EditorTestContext<'a> {
         self.assert_selections(expected_selections, expected_marked_text)
     }
 
-    #[track_caller]
-    fn assert_selections(
-        &mut self,
-        expected_selections: Vec<Range<usize>>,
-        expected_marked_text: String,
-    ) {
-        let actual_selections = self
-            .editor
+    fn editor_selections(&self) -> Vec<Range<usize>> {
+        self.editor
             .read_with(self.cx, |editor, cx| editor.selections.all::<usize>(cx))
             .into_iter()
             .map(|s| {
@@ -265,12 +263,22 @@ impl<'a> EditorTestContext<'a> {
                     s.start..s.end
                 }
             })
-            .collect::<Vec<_>>();
+            .collect::<Vec<_>>()
+    }
+
+    #[track_caller]
+    fn assert_selections(
+        &mut self,
+        expected_selections: Vec<Range<usize>>,
+        expected_marked_text: String,
+    ) {
+        let actual_selections = self.editor_selections();
         let actual_marked_text =
             generate_marked_text(&self.buffer_text(), &actual_selections, true);
         if expected_selections != actual_selections {
             panic!(
                 indoc! {"
+
                     {}Editor has unexpected selections.
 
                     Expected selections: