diff --git a/src/browser/renderer/shared/RendererUtils.test.ts b/src/browser/renderer/shared/RendererUtils.test.ts
new file mode 100644
index 00000000..e933af52
--- /dev/null
+++ b/src/browser/renderer/shared/RendererUtils.test.ts
@@ -0,0 +1,45 @@
+import { computeVarinatOffset } from 'browser/renderer/shared/RendererUtils';
+import { assert } from 'chai';
+
+describe('RendererUtils', () => {
+  it('computeVarinatOffset', () => {
+    const cellWidth = 11;
+    const doubleCellWidth = 22;
+    let line = 1;
+    let varinatOffset = 0;
+
+    // should line 1
+    // =,_,=_,=_,
+    let cells = [cellWidth, cellWidth, doubleCellWidth, doubleCellWidth];
+    let result = [1, 0, 0, 0];
+    for (let index = 0; index < cells.length; index++) {
+      const cell = cells[index];
+      varinatOffset = computeVarinatOffset(cell, line, varinatOffset);
+      assert.equal(varinatOffset, result[index]);
+    }
+
+    // should line 2
+    // ==__==__==_,_==__==__==,__==__==__==__==__==__,==__==__==__==__==__==,
+    line = 2;
+    varinatOffset = 0;
+    cells = [cellWidth, cellWidth, doubleCellWidth, doubleCellWidth];
+    result = [3, 2, 0 ,2];
+    for (let index = 0; index < cells.length; index++) {
+      const cell = cells[index];
+      varinatOffset = computeVarinatOffset(cell, line, varinatOffset);
+      assert.equal(varinatOffset, result[index]);
+    }
+
+    // should line 3
+    // ===___===__,_===___===_,__===___===___===___==,=___===___===___===___,
+    line = 3;
+    varinatOffset = 0;
+    cells = [cellWidth, cellWidth, doubleCellWidth, doubleCellWidth];
+    result = [5, 4, 2, 0];
+    for (let index = 0; index < cells.length; index++) {
+      const cell = cells[index];
+      varinatOffset = computeVarinatOffset(cell, line, varinatOffset);
+      assert.equal(varinatOffset, result[index]);
+    }
+  });
+});