test_runner: print tree correctly - Windows

Author: pmarchini

lib/internal/test_runner/utils.js

@@ -516,7 +516,7 @@ function getCoverageReport(pad, summary, symbol, color, table) {
     for (const key in tree) {
       if (tree[key].file) {
         const file = tree[key].file;
-        const fileName = ArrayPrototypePop(StringPrototypeSplit(file.path, '/'));
+        const fileName = ArrayPrototypePop(StringPrototypeSplit(file.path, sep));
 
         let fileCoverage = 0;
         const coverages = ArrayPrototypeMap(kColumnsKeys, (columnKey) => {