diff --git a/lib/classes/PluginManager.test.js b/lib/classes/PluginManager.test.js
index d3ebcfc01..7fef195e4 100644
--- a/lib/classes/PluginManager.test.js
+++ b/lib/classes/PluginManager.test.js
@@ -561,6 +561,14 @@ describe('PluginManager', () => {
       expect(pluginManager.plugins[0]).to.be.instanceof(SynchronousPluginMock);
     });
 
+    it('should not duplicate plugins', () => {
+      pluginManager.addPlugin(SynchronousPluginMock);
+      pluginManager.addPlugin(SynchronousPluginMock);
+
+      expect(pluginManager.plugins[0]).to.be.instanceof(SynchronousPluginMock);
+      expect(pluginManager.plugins.length).to.equal(1);
+    });
+
     it('should load the plugin commands', () => {
       pluginManager.addPlugin(SynchronousPluginMock);