diff --git a/spec/px-to-viewport.spec.js b/spec/px-to-viewport.spec.js
index 23632e2..aad1213 100644
--- a/spec/px-to-viewport.spec.js
+++ b/spec/px-to-viewport.spec.js
@@ -196,3 +196,51 @@ describe('minPixelValue', function () {
       expect(processed).toBe(expected);
   });
 });
+
+describe('exclude', function () {
+  var rules = '.rule { border: 1px solid #000; font-size: 16px; margin: 1px 10px; }';
+  var covered = '.rule { border: 1px solid #000; font-size: 5vw; margin: 1px 3.125vw; }'
+  it('when using regex at the time, the style should not be overwritten.', function () {
+    var options = {
+      exclude: /node_modules/
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/node_modules/main.css'
+    }).css;
+
+    expect(processed).toBe(rules);
+  });
+
+  it('when using regex at the time, the style should be overwritten.', function () {
+    var options = {
+      exclude: /node_modules/
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/example/main.css'
+    }).css;
+
+    expect(processed).toBe(covered);
+  });
+
+  it('when using array at the time, the style should not be overwritten.', function () {
+    var options = {
+      exclude: [/node_modules/, /exclude/]
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/exclude/main.css'
+    }).css;
+
+    expect(processed).toBe(rules);
+  });
+
+  it('when using array at the time, the style should be overwritten.', function () {
+    var options = {
+      exclude: [/node_modules/, /exclude/]
+    }
+    var processed = postcss(pxToViewport(options)).process(rules, {
+      from: '/example/main.css'
+    }).css;
+
+    expect(processed).toBe(covered);
+  });
+});