diff --git a/packages/grammar-selector/spec/grammar-selector-spec.js b/packages/grammar-selector/spec/grammar-selector-spec.js
index aaea64b42..460994053 100644
--- a/packages/grammar-selector/spec/grammar-selector-spec.js
+++ b/packages/grammar-selector/spec/grammar-selector-spec.js
@@ -27,25 +27,21 @@ describe('GrammarSelector', () => {
 
   describe('when grammar-selector:show is triggered', () =>
     it('displays a list of all the available grammars', async () => {
-      atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
-      await SelectListView.getScheduler().getNextUpdatePromise()
-
-      const grammarView = atom.workspace.getModalPanels()[0].getItem().element
+      const grammarView = (await getGrammarView(editor)).element
 
       // -1 for removing nullGrammar, +1 for adding "Auto Detect"
+      // Tree-sitter names the regex and JSDoc grammars
       expect(grammarView.querySelectorAll('li').length).toBe(atom.grammars.grammars.filter(g => g.name).length)
       expect(grammarView.querySelectorAll('li')[0].textContent).toBe('Auto Detect')
       expect(grammarView.textContent.includes('source.a')).toBe(false)
       grammarView.querySelectorAll('li').forEach(li => expect(li.textContent).not.toBe(atom.grammars.nullGrammar.name))
+      expect(grammarView.textContent.includes("Tree-sitter")).toBe(true) // check we are showing and labelling Tree-sitter grammars
     })
   )
 
   describe('when a grammar is selected', () =>
     it('sets the new grammar on the editor', async () => {
-      atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
-      await SelectListView.getScheduler().getNextUpdatePromise()
-
-      const grammarView = atom.workspace.getModalPanels()[0].getItem()
+      const grammarView = await getGrammarView(editor)
       grammarView.props.didConfirmSelection(textGrammar)
       expect(editor.getGrammar()).toBe(textGrammar)
     })
@@ -53,17 +49,11 @@ describe('GrammarSelector', () => {
 
   describe('when auto-detect is selected', () =>
     it('restores the auto-detected grammar on the editor', async () => {
-      atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
-      await SelectListView.getScheduler().getNextUpdatePromise()
-
-      let grammarView = atom.workspace.getModalPanels()[0].getItem()
+      let grammarView = await getGrammarView(editor)
       grammarView.props.didConfirmSelection(textGrammar)
       expect(editor.getGrammar()).toBe(textGrammar)
 
-      atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
-      await SelectListView.getScheduler().getNextUpdatePromise()
-
-      grammarView = atom.workspace.getModalPanels()[0].getItem()
+      grammarView = await getGrammarView(editor)
       grammarView.props.didConfirmSelection(grammarView.items[0])
       expect(editor.getGrammar()).toBe(jsGrammar)
     })
@@ -72,10 +62,7 @@ describe('GrammarSelector', () => {
   describe("when the editor's current grammar is the null grammar", () =>
     it('displays Auto Detect as the selected grammar', async () => {
       editor.setGrammar(atom.grammars.nullGrammar)
-      atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
-      await SelectListView.getScheduler().getNextUpdatePromise()
-
-      const grammarView = atom.workspace.getModalPanels()[0].getItem().element
+      const grammarView = (await getGrammarView(editor)).element
       expect(grammarView.querySelector('li.active').textContent).toBe('Auto Detect')
     })
   )
@@ -85,10 +72,7 @@ describe('GrammarSelector', () => {
       editor = await atom.workspace.open()
       expect(editor.getGrammar()).not.toBe(jsGrammar)
 
-      atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
-      await SelectListView.getScheduler().getNextUpdatePromise()
-
-      const grammarView = atom.workspace.getModalPanels()[0].getItem()
+      const grammarView = await getGrammarView(editor)
       grammarView.props.didConfirmSelection(jsGrammar)
       expect(editor.getGrammar()).toBe(jsGrammar)
     })
@@ -170,6 +154,52 @@ describe('GrammarSelector', () => {
       })
     )
 
+    describe('when toggling hideDuplicateTextMateGrammars', () => {
+      it('shows only the Tree-sitter if true and both exist', async () => {
+        // the main JS grammar has both a TextMate and Tree-sitter implementation
+        atom.config.set('grammar-selector.hideDuplicateTextMateGrammars', true)
+        const grammarView = await getGrammarView(editor)
+        const observedNames = new Set()
+        grammarView.element.querySelectorAll('li').forEach(li => {
+          const name = li.getAttribute('data-grammar')
+          expect(observedNames.has(name)).toBe(false)
+          observedNames.add(name)
+        })
+
+        // check the seen JS is actually the Tree-sitter one
+        const list = atom.workspace.getModalPanels()[0].item
+        for (const item of list.items) {
+          if (item.name === "JavaScript") {
+            expect(item.constructor.name === "TreeSitterGrammar")
+          }
+        }
+      })
+
+      it('shows both if false', async () => {
+        atom.config.set('grammar-selector.hideDuplicateTextMateGrammars', false)
+        const grammarView = await getGrammarView(editor)
+        let jsCount = 0
+        grammarView.element.querySelectorAll('li').forEach(li => {
+          const name = li.getAttribute('data-grammar')
+          if (name === "JavaScript") jsCount++
+        })
+        expect(jsCount).toBe(2)
+      })
+    })
+
+    describe('for every Tree-sitter grammar', () => {
+      it('adds a label to identify it as Tree-sitter', async () => {
+        const grammarView = await getGrammarView(editor)
+        const elements = grammarView.element.querySelectorAll('li')
+        const listItems = atom.workspace.getModalPanels()[0].item.items
+        for (let i = 0; i < listItems.length; i++) {
+          if (listItems[i].constructor.name === "TreeSitterGrammar") {
+            expect(elements[i].childNodes[1].childNodes[0].className.startsWith('grammar-selector-parser')).toBe(true)
+          }
+        }
+      })
+    })
+
     describe('when clicked', () =>
       it('shows the grammar selector modal', () => {
         const eventHandler = jasmine.createSpy('eventHandler')
@@ -193,3 +223,9 @@ function getTooltipText (element) {
   const [tooltip] = atom.tooltips.findTooltips(element)
   return tooltip.getTitle()
 }
+
+async function getGrammarView (editor) {
+  atom.commands.dispatch(editor.getElement(), 'grammar-selector:show')
+  await SelectListView.getScheduler().getNextUpdatePromise()
+  return atom.workspace.getModalPanels()[0].getItem()
+}