test: fix test

Author: azu

test/fixer-test.js

@@ -3,22 +3,31 @@
 import assert from "assert";
 import preset from "../src/index";
 import { TextLintCore } from "textlint";
+import path from "path";
 import fs from "fs";
 
 describe("fixer-test", function () {
     it("should convert expected", function () {
-        const expected = fs.readFileSync(__dirname + "/fixtures/output.md", "utf-8");
+        const expected = fs.readFileSync(path.join(__dirname, "/fixtures/output.md"), "utf-8");
         const textlint = new TextLintCore();
         // all true
         textlint.setupRules(preset.rules);
-        return textlint.fixFile(__dirname + "/fixtures/input.md").then((result) => {
+        return textlint.fixFile(path.join(__dirname, "/fixtures/input.md")).then((result) => {
             assert.equal(result.remainingMessages.length, 0);
             const inputs = result.output.split("\n");
             const outputs = expected.split("\n");
             for (var i = 0; i < inputs.length; i++) {
                 const input = inputs[i];
                 const output = outputs[i];
-                assert.strictEqual(input, output);
+                assert.strictEqual(
+                    input,
+                    output,
+                    `mismatch at line ${i}
+
+at ${path.join(__dirname, "/fixtures/input.md")}:${i}
+at ${path.join(__dirname, "/fixtures/output.md")}:${i}
+`
+                );
             }
         });
     });