Add regression tests for tab stops at ends of snippets

Adds tests from atom#261 for an issue that has been since fixed.

Author: Ingramz

spec/snippets-spec.coffee

@@ -165,6 +165,14 @@ describe "Snippets extension", ->
                 ${2:placeholder ending second line}
             """
 
+          "tab stops at the ends of snippets":
+            prefix: "t6b"
+            body: "$1expanded$0"
+
+          "tab stops at the ends of snippets - alternative":
+            prefix: "t6c"
+            body: "$0expanded$1"
+
           "contains empty lines":
             prefix: "t7"
             body: """
@@ -591,6 +599,28 @@ describe "Snippets extension", ->
         simulateTabKeyEvent()
         expect(editor.lineTextForBufferRow(0)).toBe "first line"
 
+      it "does not remember the tab stops when the whole snippet has been undone (regression)", ->
+        editor.insertText 't6b\n'
+        editor.setCursorBufferPosition [0, 3]
+        simulateTabKeyEvent()
+        expect(editor.lineTextForBufferRow(0)).toBe "expanded"
+        editor.undo()
+        expect(editor.lineTextForBufferRow(0)).toBe "t6b"
+        simulateTabKeyEvent()
+        expect(editor.lineTextForBufferRow(0)).toBe "expanded"
+        expect(editor.getCursorBufferPosition()).toEqual([0, 0])
+
+      it "does not remember the tab stops when the whole snippet has been undone (regression, alternative version)", ->
+        editor.insertText 't6c\n'
+        editor.setCursorBufferPosition [0, 3]
+        simulateTabKeyEvent()
+        expect(editor.lineTextForBufferRow(0)).toBe "expanded"
+        editor.undo()
+        expect(editor.lineTextForBufferRow(0)).toBe "t6c"
+        simulateTabKeyEvent()
+        expect(editor.lineTextForBufferRow(0)).toBe "expanded"
+        expect(editor.getCursorBufferPosition()).toEqual([0, 8])
+
     describe "when the prefix contains non-word characters", ->
       it "selects the non-word characters as part of the prefix", ->
         editor.insertText("@unique")