diff --git a/spec/lines-yardstick-spec.coffee b/spec/lines-yardstick-spec.coffee
new file mode 100644
index 000000000..68af04da4
--- /dev/null
+++ b/spec/lines-yardstick-spec.coffee
@@ -0,0 +1,136 @@
+LinesYardstick = require "../src/lines-yardstick"
+
+describe "LinesYardstick", ->
+  [editor, mockPresenter, mockLineNodesProvider, createdLineNodes, linesYardstick] = []
+
+  beforeEach ->
+    waitsForPromise ->
+      atom.packages.activatePackage('language-javascript')
+
+    waitsForPromise ->
+      atom.project.open('sample.js').then (o) -> editor = o
+
+    runs ->
+      createdLineNodes = []
+      availableScreenRows = {}
+      screenRowsToMeasure = []
+
+      buildLineNode = (screenRow) ->
+        tokenizedLine = editor.tokenizedLineForScreenRow(screenRow)
+        iterator = tokenizedLine.getTokenIterator()
+        lineNode = document.createElement("div")
+        lineNode.style.whiteSpace = "pre"
+        while iterator.next()
+          span = document.createElement("span")
+          span.className = iterator.getScopes().join(' ').replace(/\.+/g, ' ')
+          span.textContent = iterator.getText()
+          lineNode.appendChild(span)
+
+        jasmine.attachToDOM(lineNode)
+        createdLineNodes.push(lineNode)
+        lineNode
+
+      mockPresenter =
+        isBatching: -> true
+        setScreenRowsToMeasure: (screenRows) -> screenRowsToMeasure = screenRows
+        getPreMeasurementState: ->
+          state = {}
+          for screenRow in screenRowsToMeasure
+            tokenizedLine = editor.tokenizedLineForScreenRow(screenRow)
+            state[tokenizedLine.id] = screenRow
+          state
+
+      mockLineNodesProvider =
+        updateSync: (state) -> availableScreenRows = state
+        lineNodeForLineIdAndScreenRow: (lineId, screenRow) ->
+          if availableScreenRows[lineId] isnt screenRow
+            throw new Error("No line node found!")
+
+          buildLineNode(screenRow)
+
+      editor.setLineHeightInPixels(14)
+      linesYardstick = new LinesYardstick(editor, mockPresenter, mockLineNodesProvider)
+
+  afterEach ->
+    lineNode.remove() for lineNode in createdLineNodes
+    atom.themes.removeStylesheet('test')
+
+  describe "::pixelPositionForScreenPosition(screenPosition)", ->
+    it "converts screen positions to pixel positions", ->
+      atom.styles.addStyleSheet """
+      * {
+        font-size: 12px;
+        font-family: monospace;
+      }
+      .function {
+        font-size: 16px
+      }
+      """
+
+      expect(linesYardstick.pixelPositionForScreenPosition([0, 0])).toEqual({left: 0, top: 0})
+      expect(linesYardstick.pixelPositionForScreenPosition([0, 1])).toEqual({left: 7, top: 0})
+      expect(linesYardstick.pixelPositionForScreenPosition([0, 5])).toEqual({left: 38, top: 0})
+      expect(linesYardstick.pixelPositionForScreenPosition([1, 6])).toEqual({left: 42, top: 14})
+      expect(linesYardstick.pixelPositionForScreenPosition([1, 9])).toEqual({left: 72, top: 14})
+      expect(linesYardstick.pixelPositionForScreenPosition([2, Infinity])).toEqual({left: 280, top: 28})
+
+    it "reuses already computed pixel positions unless it is invalidated", ->
+      atom.styles.addStyleSheet """
+      * {
+        font-size: 16px;
+        font-family: monospace;
+      }
+      """
+
+      expect(linesYardstick.pixelPositionForScreenPosition([1, 2])).toEqual({left: 20, top: 14})
+      expect(linesYardstick.pixelPositionForScreenPosition([2, 6])).toEqual({left: 60, top: 28})
+      expect(linesYardstick.pixelPositionForScreenPosition([5, 10])).toEqual({left: 100, top: 70})
+
+      atom.styles.addStyleSheet """
+      * {
+        font-size: 20px;
+      }
+      """
+
+      expect(linesYardstick.pixelPositionForScreenPosition([1, 2])).toEqual({left: 20, top: 14})
+      expect(linesYardstick.pixelPositionForScreenPosition([2, 6])).toEqual({left: 60, top: 28})
+      expect(linesYardstick.pixelPositionForScreenPosition([5, 10])).toEqual({left: 100, top: 70})
+
+      linesYardstick.invalidateCache()
+
+      expect(linesYardstick.pixelPositionForScreenPosition([1, 2])).toEqual({left: 24, top: 14})
+      expect(linesYardstick.pixelPositionForScreenPosition([2, 6])).toEqual({left: 72, top: 28})
+      expect(linesYardstick.pixelPositionForScreenPosition([5, 10])).toEqual({left: 120, top: 70})
+
+    describe "::screenPositionForPixelPosition(pixelPosition)", ->
+      it "converts pixel positions to screen positions", ->
+        atom.styles.addStyleSheet """
+        * {
+          font-size: 12px;
+          font-family: monospace;
+        }
+        .function {
+          font-size: 16px
+        }
+        """
+
+        expect(linesYardstick.screenPositionForPixelPosition({top: 0, left: 12.5})).toEqual([0, 2])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 14, left: 17.8})).toEqual([1, 3])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 28, left: 100})).toEqual([2, 14])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 32, left: 24.3})).toEqual([2, 3])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 46, left: 66.5})).toEqual([3, 9])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 80, left: 99.9})).toEqual([5, 14])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 80, left: 221.5})).toEqual([5, 29])
+        expect(linesYardstick.screenPositionForPixelPosition({top: 80, left: 222})).toEqual([5, 30])
+
+      it "clips pixel positions above buffer start", ->
+        expect(linesYardstick.screenPositionForPixelPosition(top: -Infinity, left: -Infinity)).toEqual [0, 0]
+        expect(linesYardstick.screenPositionForPixelPosition(top: -Infinity, left: Infinity)).toEqual [0, 0]
+        expect(linesYardstick.screenPositionForPixelPosition(top: -1, left: Infinity)).toEqual [0, 0]
+        expect(linesYardstick.screenPositionForPixelPosition(top: 0, left: Infinity)).toEqual [0, 29]
+
+      it "clips pixel positions below buffer end", ->
+        expect(linesYardstick.screenPositionForPixelPosition(top: Infinity, left: -Infinity)).toEqual [12, 2]
+        expect(linesYardstick.screenPositionForPixelPosition(top: Infinity, left: Infinity)).toEqual [12, 2]
+        expect(linesYardstick.screenPositionForPixelPosition(top: (editor.getLastScreenRow() + 1) * 14, left: 0)).toEqual [12, 2]
+        expect(linesYardstick.screenPositionForPixelPosition(top: editor.getLastScreenRow() * 14, left: 0)).toEqual [12, 0]
diff --git a/spec/text-editor-component-spec.coffee b/spec/text-editor-component-spec.coffee
index caddb0ee5..6f53ee4e2 100644
--- a/spec/text-editor-component-spec.coffee
+++ b/spec/text-editor-component-spec.coffee
@@ -3558,19 +3558,6 @@ describe "TextEditorComponent", ->
         nextAnimationFrame()
         expect(wrapperNode.getScrollTop()).toBe 0
 
-  describe "::screenPositionForPixelPosition(pixelPosition)", ->
-    it "clips pixel positions above buffer start", ->
-      expect(component.screenPositionForPixelPosition(top: -Infinity, left: -Infinity)).toEqual [0, 0]
-      expect(component.screenPositionForPixelPosition(top: -Infinity, left: Infinity)).toEqual [0, 0]
-      expect(component.screenPositionForPixelPosition(top: -1, left: Infinity)).toEqual [0, 0]
-      expect(component.screenPositionForPixelPosition(top: 0, left: Infinity)).toEqual [0, 29]
-
-    it "clips pixel positions below buffer end", ->
-      expect(component.screenPositionForPixelPosition(top: Infinity, left: -Infinity)).toEqual [12, 2]
-      expect(component.screenPositionForPixelPosition(top: Infinity, left: Infinity)).toEqual [12, 2]
-      expect(component.screenPositionForPixelPosition(top: component.getScrollHeight() + 1, left: 0)).toEqual [12, 2]
-      expect(component.screenPositionForPixelPosition(top: component.getScrollHeight() - 1, left: 0)).toEqual [12, 0]
-
   describe "::getVisibleRowRange()", ->
     beforeEach ->
       wrapperNode.style.height = lineHeightInPixels * 8 + "px"