Add text utility spec

spec/javascripts/lib/utils/common_utils_spec.js.es6

@@ -52,6 +52,5 @@
         expect(value).toBe(null);
       });
     });
-
   });
 })();

spec/javascripts/lib/utils/text_utility_spec.js.es6

@@ -0,0 +1,25 @@
+//= require lib/utils/text_utility
+
+(() => {
+  describe('text_utility', () => {
+    describe('gl.text.getTextWidth', () => {
+      it('returns zero width when no text is passed', () => {
+        expect(gl.text.getTextWidth('')).toBe(0);
+      });
+
+      it('returns zero width when no text is passed and font is passed', () => {
+        expect(gl.text.getTextWidth('', '100px sans-serif')).toBe(0);
+      });
+
+      it('returns width when text is passed', () => {
+        expect(gl.text.getTextWidth('foo') > 0).toBe(true);
+      });
+
+      it('returns bigger width when font is larger', () => {
+        const largeFont = gl.text.getTextWidth('foo', '100px sans-serif');
+        const regular = gl.text.getTextWidth('foo', '10px sans-serif');
+        expect(largeFont > regular).toBe(true);
+      });
+    });
+  });
+})();