Make the test runner accept a argument to restrict the tests running (for debugging). Make the test runner pass the filename so it behaves like lessc - this fixed one of the tests. Also corrected the tests to run given the new format of the message

test/less-test.js

@@ -4,6 +4,8 @@ var path = require('path'),
 
 var less = require('../lib/less');
 
+var oneTestOnly = process.argv[2];
+
 less.tree.functions.add = function (a, b) {
     return new(less.tree.Dimension)(a.value + b.value);
 }
@@ -18,9 +20,12 @@ sys.puts("\n" + stylize("LESS", 'underline') + "\n");
 
 fs.readdirSync('test/less').forEach(function (file) {
     if (! /\.less/.test(file)) { return }
+    
+    var name = path.basename(file, '.less');
+    
+    if (oneTestOnly && name !== oneTestOnly) { return; }
 
     toCSS('test/less/' + file, function (err, less) {
-        var name = path.basename(file, '.less');
 
         fs.readFile(path.join('test/css', name) + '.css', 'utf-8', function (e, css) {
             sys.print("- " + name + ": ")
@@ -46,12 +51,15 @@ fs.readdirSync('test/less').forEach(function (file) {
 
 fs.readdirSync('test/less/errors').forEach(function (file) {
     if (! /\.less/.test(file)) { return }
+    
+    var name = path.basename(file, '.less');
+    
+    if (oneTestOnly && ("error/" + name) !== oneTestOnly) { return; }
 
     toCSS('test/less/errors/' + file, function (err, compiledLess) {
-        var name = path.basename(file, '.less');
-
         fs.readFile(path.join('test/less/errors', name) + '.txt', 'utf-8', function (e, expectedErr) {
             sys.print("- error/" + name + ": ");
+            expectedErr = expectedErr.replace("{path}", path.join(process.cwd(), "/test/less/errors/"));
             if (!err) {
                 if (compiledLess) {
                     sys.print(stylize("No Error", 'red'));
@@ -87,7 +95,8 @@ function toCSS(path, callback) {
 
         new(less.Parser)({
             paths: [require('path').dirname(path)],
-            optimization: 0
+            optimization: 0,
+            filename: require('path').resolve(process.cwd(), path)
         }).parse(str, function (err, tree) {
             if (err) {
                 callback(err);

test/less/errors/comment-in-selector.txt

@@ -1,2 +1,2 @@
-ParseError: Syntax Error on line 1
+ParseError: Syntax Error on line 1 in {path}comment-in-selector.less:1:20
 1 #gaga /* Comment */ span { color: red }

test/less/errors/import-no-semi.txt

@@ -1,2 +1,2 @@
-ParseError: Syntax Error on line 1
+ParseError: Syntax Error on line 1 in C:\git\less.js\test\less\errors\import-no-semi.less:1:0
 1 @import "this-statement-is-invalid.less"

test/less/errors/import-subfolder1.txt

@@ -1,3 +1,3 @@
-NameError: .mixin-not-defined is undefined in test\less\errors\mixin-not-defined.less:1:102
+NameError: .mixin-not-defined is undefined in test\less\errors\mixin-not-defined.less:11:0
 10 
-11 .mixin-not-defined();
+11 .mixin-not-defined();

test/less/errors/mixin-not-defined.txt

@@ -1,3 +1,3 @@
-NameError: .mixin-not-defined is undefined
+NameError: .mixin-not-defined is undefined in C:\git\less.js\test\less\errors\mixin-not-defined.less:11:0
 10 
 11 .mixin-not-defined();

test/less/errors/parse-error-curly-bracket.txt

@@ -1,2 +1,2 @@
-ParseError: Syntax Error on line 1
+ParseError: Syntax Error on line 1 in C:\git\less.js\test\less\errors\parse-error-curly-bracket.less:1:0
 1 }}