Replace path sep for testRegex in should_instrument

so test files don't get instrumented on windows given a pattern like /__tests__/*.js

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## master
 
+### Fixes
+
+* `[jest-runtime]` Replace path sep for testRegex in should_instrument so test
+files don't get instrumented on windows given a pattern like /__tests__/*.js
+  ([#5560](https://github.com/facebook/jest/pull/5560))
+
 ## jest 22.3.0
 
 ### Fixes

integration-tests/__tests__/coverage_remapping.test.js

@@ -11,15 +11,12 @@
 
 const {readFileSync} = require('fs');
 const path = require('path');
-const SkipOnWindows = require('../../scripts/SkipOnWindows');
 const {cleanup, run} = require('../utils');
 const runJest = require('../runJest');
 
 const dir = path.resolve(__dirname, '../coverage-remapping');
 const coverageDir = path.join(dir, 'coverage');
 
-SkipOnWindows.suite();
-
 beforeAll(() => {
   cleanup(coverageDir);
 });

packages/jest-runtime/src/should_instrument.js

@@ -11,7 +11,7 @@ import type {Path, ProjectConfig} from 'types/Config';
 import type {Options} from './script_transformer';
 
 import path from 'path';
-import {escapePathForRegex} from 'jest-regex-util';
+import {escapePathForRegex, replacePathSepForRegex} from 'jest-regex-util';
 import micromatch from 'micromatch';
 
 const MOCKS_PATTERN = new RegExp(
@@ -35,7 +35,10 @@ export default function shouldInstrument(
     return true;
   }
 
-  if (config.testRegex && filename.match(config.testRegex)) {
+  if (
+    config.testRegex &&
+    new RegExp(replacePathSepForRegex(config.testRegex)).test(filename)
+  ) {
     return false;
   }