Fix jest snapshot testing on windows

Summary:
Fixes #19370

Applied changes to existing project that uses jest snapshot testing. Testing was broken before and now works.

To verify: Run any snapshot test containing an image reference on Windows before and after this PR.

[WINDOWS][BUGFIX][jest] - Fixed jest snapshot testing on windows
Closes https://github.com/facebook/react-native/pull/19496

Differential Revision: D8195947

Pulled By: hramos

fbshipit-source-id: 909b5fe7cfd8c6286baf161a227a359854a37603

jest-preset.json

@@ -15,7 +15,7 @@
   ],
   "transform": {
     "^.+\\.js$": "babel-jest",
-    "^[./a-zA-Z0-9$_-]+\\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$": "<rootDir>/node_modules/react-native/jest/assetFileTransformer.js"
+    "^.+\\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$": "<rootDir>/node_modules/react-native/jest/assetFileTransformer.js"
   },
   "transformIgnorePatterns": [
     "node_modules/(?!(jest-)?react-native|react-clone-referenced-element)"

jest/assetFileTransformer.js

@@ -21,7 +21,10 @@ module.exports = {
   // the Jest snapshot.
   process: (_, filename) =>
     `module.exports = {
-      testUri: ${JSON.stringify(path.relative(__dirname, filename))}
+      testUri: 
+        ${JSON.stringify(
+          path.relative(__dirname, filename).replace(/\\/g, '/'),
+        )}
     };`,
   getCacheKey: createCacheKeyFunction([__filename]),
 };

package.json

@@ -20,7 +20,7 @@
   },
   "jest": {
     "transform": {
-      "^[./a-zA-Z0-9$_-]+\\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$": "<rootDir>/jest/assetFileTransformer.js",
+      "^.+\\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$": "<rootDir>/jest/assetFileTransformer.js",
       ".*": "./jest/preprocessor.js"
     },
     "setupFiles": [