diff --git a/src/servo/text/text_run.rs b/src/servo/text/text_run.rs
index 75a87a70f81..590ff2ec246 100644
--- a/src/servo/text/text_run.rs
+++ b/src/servo/text/text_run.rs
@@ -1,5 +1,8 @@
+import geom::point::Point2D;
+import geom::size::Size2D;
+import gfx::geometry::{au, px_to_au};
 import libc::{c_void};
-import font::font;
+import font::{font, create_test_font};
 import glyph::glyph;
 import shaper::shape_text;
 
@@ -10,5 +13,25 @@ class text_run {
     new(font: &font, text: str) {
         self.glyphs = shape_text(font, text);
     }
+
+    fn size() -> Size2D<au> {
+        let height = px_to_au(14);
+        let pen_start_x = px_to_au(0);
+        let pen_start_y = height;
+        let pen_start = Point2D(pen_start_x, pen_start_y);
+        let pen_end = self.glyphs.foldl(pen_start) { |cur, glyph|
+            Point2D(cur.x.add(glyph.pos.offset.x).add(glyph.pos.advance.x),
+                    cur.y.add(glyph.pos.offset.y).add(glyph.pos.advance.y))
+        };
+        ret Size2D(pen_end.x, pen_end.y);
+    }
 }
 
+fn should_calculate_the_total_size() {
+    #[test];
+
+    let font = create_test_font();
+    let run = text_run(&font, "firecracker");
+    let expected = Size2D(px_to_au(110), px_to_au(14));
+    assert run.size() == expected;
+}