diff --git a/Gruntfile.js b/Gruntfile.js
index d428142d..0b5c200d 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -252,20 +252,44 @@ module.exports = function (grunt) {
                     outfile: 'tmp/browser/test-runner-post-processor.html'
                 }
             },
-            postProcessorPLugin: {
+            postProcessorPlugin: {
                 src: ['test/browser/less/postProcessorPlugin/*.less'],
                 options: {
                     helpers: 'test/browser/runner-postProcessorPlugin-options.js',
                     specs: 'test/browser/runner-postProcessorPlugin.js',
                     outfile: 'tmp/browser/test-runner-post-processor-plugin.html'
                 }
-            }
+            },
+            preProcessorPlugin: {
+                src: ['test/browser/less/preProcessorPlugin/*.less'],
+                options: {
+                    helpers: 'test/browser/runner-preProcessorPlugin-options.js',
+                    specs: 'test/browser/runner-preProcessorPlugin.js',
+                    outfile: 'tmp/browser/test-runner-pre-processor-plugin.html'
+                }
+            },
+            visitorPlugin: {
+                src: ['test/browser/less/visitorPlugin/*.less'],
+                options: {
+                    helpers: 'test/browser/runner-VisitorPlugin-options.js',
+                    specs: 'test/browser/runner-VisitorPlugin.js',
+                    outfile: 'tmp/browser/test-runner-visitor-plugin.html'
+                }
+            },
+            filemanagerPlugin: {
+                src: ['test/browser/less/filemanagerPlugin/*.less'],
+                options: {
+                    helpers: 'test/browser/runner-filemanagerPlugin-options.js',
+                    specs: 'test/browser/runner-filemanagerPlugin.js',
+                    outfile: 'tmp/browser/test-runner-filemanager-plugin.html'
+                }
+            }            
         },
 
         'saucelabs-jasmine': {
             all: {
                 options: {
-                    urls: ["post-processor-plugin","post-processor", "global-vars", "modify-vars", "production", "rootpath-relative",
+                    urls: ["filemanager-plugin","visitor-plugin","pre-processor-plugin","post-processor-plugin","post-processor", "global-vars", "modify-vars", "production", "rootpath-relative",
                            "rootpath", "relative-urls", "browser", "no-js-errors", "legacy", "strict-units"
                     ].map(function(testName) {
                         return "http://localhost:8081/tmp/browser/test-runner-" + testName + ".html";
diff --git a/dist/less.js b/dist/less.js
index 169c71cd..24976442 100644
--- a/dist/less.js
+++ b/dist/less.js
@@ -446,8 +446,11 @@ module.exports = function(options, logger) {
     };
 
     FileManager.prototype.loadFile = function loadFile(filename, currentDirectory, options, environment, callback) {
+        
+        console.log('loading...' + currentDirectory + filename);
+        
         if (currentDirectory && !this.isPathAbsolute(filename)) {
-            filename = currentDirectory + filename;
+            filename = ;
         }
 
         options = options || {};
@@ -9846,4 +9849,4 @@ if (typeof Promise === 'undefined') {
 require('./polyfill-done.js');
 
 },{"./lib/core.js":89,"./lib/es6-extensions.js":90,"./polyfill-done.js":92,"asap":91}]},{},[2])(2)
-});
\ No newline at end of file
+});
diff --git a/lib/less-browser/index.js b/lib/less-browser/index.js
index ffdfd9db..c6dc4502 100644
--- a/lib/less-browser/index.js
+++ b/lib/less-browser/index.js
@@ -27,7 +27,7 @@ module.exports = function(window, options) {
 
     var typePattern = /^text\/(x-)?less$/;
 
-    function postProcessCSS(styles) {
+    function postProcessCSS(styles) { // deprecated, use a plugin for postprocesstasks
         if (options.postProcessor && typeof options.postProcessor === 'function') {
             styles = options.postProcessor.call(styles, styles) || styles;
         }
diff --git a/test/browser/css/filemanagerPlugin/filemanager.css b/test/browser/css/filemanagerPlugin/filemanager.css
new file mode 100644
index 00000000..6446ebfd
--- /dev/null
+++ b/test/browser/css/filemanagerPlugin/filemanager.css
@@ -0,0 +1,3 @@
+.test {
+  color: red;
+}
diff --git a/test/browser/css/preProcessorPlugin/preProcessor.css b/test/browser/css/preProcessorPlugin/preProcessor.css
new file mode 100644
index 00000000..6446ebfd
--- /dev/null
+++ b/test/browser/css/preProcessorPlugin/preProcessor.css
@@ -0,0 +1,3 @@
+.test {
+  color: red;
+}
diff --git a/test/browser/css/visitorPlugin/visitor.css b/test/browser/css/visitorPlugin/visitor.css
new file mode 100644
index 00000000..6446ebfd
--- /dev/null
+++ b/test/browser/css/visitorPlugin/visitor.css
@@ -0,0 +1,3 @@
+.test {
+  color: red;
+}
diff --git a/test/browser/less/filemanagerPlugin/colors.test b/test/browser/less/filemanagerPlugin/colors.test
new file mode 100644
index 00000000..b605e2f0
--- /dev/null
+++ b/test/browser/less/filemanagerPlugin/colors.test
@@ -0,0 +1 @@
+//@color: red;
diff --git a/test/browser/less/filemanagerPlugin/filemanager.less b/test/browser/less/filemanagerPlugin/filemanager.less
new file mode 100644
index 00000000..75896dbd
--- /dev/null
+++ b/test/browser/less/filemanagerPlugin/filemanager.less
@@ -0,0 +1,4 @@
+@import "test.test";
+.test {
+    color: red;
+}
diff --git a/test/browser/less/preProcessorPlugin/preProcessor.less b/test/browser/less/preProcessorPlugin/preProcessor.less
new file mode 100644
index 00000000..50183ea2
--- /dev/null
+++ b/test/browser/less/preProcessorPlugin/preProcessor.less
@@ -0,0 +1,3 @@
+.test {
+    color: @color;
+}
diff --git a/test/browser/less/visitorPlugin/visitor.less b/test/browser/less/visitorPlugin/visitor.less
new file mode 100644
index 00000000..bd2da3e8
--- /dev/null
+++ b/test/browser/less/visitorPlugin/visitor.less
@@ -0,0 +1,4 @@
+.test {
+    color: red;
+    -some-aribitrary-property: value;
+}
diff --git a/test/browser/runner-VisitorPlugin-options.js b/test/browser/runner-VisitorPlugin-options.js
new file mode 100644
index 00000000..4fa04c60
--- /dev/null
+++ b/test/browser/runner-VisitorPlugin-options.js
@@ -0,0 +1,29 @@
+RemoveProperty = function(less) {
+    this._visitor = new less.visitors.Visitor(this);
+};
+
+RemoveProperty.prototype = {
+    isReplacing: true,
+    run: function (root) {
+        return this._visitor.visit(root);
+    },
+    visitRule: function (ruleNode, visitArgs) {
+        if (ruleNode.name != '-some-aribitrary-property')
+        {
+            return ruleNode;
+        }
+        else {
+            return [];
+        }
+    }
+};
+
+var VisitorPlugin = {
+    install: function(less, pluginManager) {
+        pluginManager.addVisitor( new RemoveProperty(less));
+    }
+};
+
+var less = {logLevel: 4,
+    errorReporting: "console",
+    plugins: [VisitorPlugin]};
diff --git a/test/browser/runner-VisitorPlugin.js b/test/browser/runner-VisitorPlugin.js
new file mode 100644
index 00000000..3c4287a2
--- /dev/null
+++ b/test/browser/runner-VisitorPlugin.js
@@ -0,0 +1,3 @@
+describe("less.js Visitor Plugin", function() {
+    testLessEqualsInDocument();
+});
diff --git a/test/browser/runner-filemanagerPlugin-options.js b/test/browser/runner-filemanagerPlugin-options.js
new file mode 100644
index 00000000..3b9fc52d
--- /dev/null
+++ b/test/browser/runner-filemanagerPlugin-options.js
@@ -0,0 +1,29 @@
+var plugin = function(less) {
+
+    var FileManager = less.FileManager;
+
+    function TestFileManager() {
+    };
+
+    TestFileManager = new FileManager();
+
+    TestFileManager.loadFile = function (filename, currentDirectory, options, environment, callback) {
+        if (filename.match(/.*\.test$/)) {
+            return less.environment.fileManagers[0].loadFile("colors.test", currentDirectory, options, environment, callback);
+        }
+        return less.environment.fileManagers[0].loadFile(filename, currentDirectory, options, environment, callback);
+    };
+
+    return TestFileManager;
+};
+
+var AddFilePlugin = {
+    install: function(less, pluginManager) {
+        less.environment.addFileManager(new plugin(less));
+    }
+};
+
+var less = {logLevel: 4,
+    errorReporting: "console",
+    plugins: [AddFilePlugin]
+    };
diff --git a/test/browser/runner-filemanagerPlugin.js b/test/browser/runner-filemanagerPlugin.js
new file mode 100644
index 00000000..1ede4157
--- /dev/null
+++ b/test/browser/runner-filemanagerPlugin.js
@@ -0,0 +1,3 @@
+describe("less.js filemanager Plugin", function() {
+    testLessEqualsInDocument();
+});
diff --git a/test/browser/runner-postProcessor.js b/test/browser/runner-postProcessor.js
index a104a59b..64937669 100644
--- a/test/browser/runner-postProcessor.js
+++ b/test/browser/runner-postProcessor.js
@@ -1,3 +1,3 @@
-describe("less.js postProcessor", function() {
+describe("less.js postProcessor (deprecated)", function() {
     testLessEqualsInDocument();
 });
diff --git a/test/browser/runner-preProcessorPlugin-options.js b/test/browser/runner-preProcessorPlugin-options.js
new file mode 100644
index 00000000..6d0fd433
--- /dev/null
+++ b/test/browser/runner-preProcessorPlugin-options.js
@@ -0,0 +1,22 @@
+var preProcessor = function() {};
+
+preProcessor.prototype = {
+    process : function (src, extra) {
+        var injected = '@color: red;\n';
+        var ignored = extra.imports.contentsIgnoredChars;
+        var fileInfo = extra.fileInfo;
+        ignored[fileInfo.filename] = ignored[fileInfo.filename] || 0;
+        ignored[fileInfo.filename] += injected.length;
+        return injected + src;
+    }
+};
+
+var preProcessorPlugin = {
+    install: function(less, pluginManager) {
+        pluginManager.addPreProcessor( new preProcessor());
+    }
+};
+
+var less = {logLevel: 4,
+    errorReporting: "console",
+    plugins: [preProcessorPlugin]};
diff --git a/test/browser/runner-preProcessorPlugin.js b/test/browser/runner-preProcessorPlugin.js
new file mode 100644
index 00000000..4382396e
--- /dev/null
+++ b/test/browser/runner-preProcessorPlugin.js
@@ -0,0 +1,3 @@
+describe("less.js preProcessor Plugin", function() {
+    testLessEqualsInDocument();
+});