Flush atomic file writes

test/cli/samples/watch/watch-config-early-update/_config.js

@@ -1,6 +1,6 @@
 const fs = require('fs');
 const path = require('path');
-const { atomicWriteFileSync } = require('../../../../utils');
+const { atomicWriteFileSync, syncFile } = require('../../../../utils');
 
 let configFile;
 
@@ -49,6 +49,7 @@ module.exports = {
 		    };
 		    `
 			);
+			syncFile(configFile);
 			return false;
 		}
 		if (data.includes(`created _actual${path.sep}output2.js`)) {

test/utils.js

@@ -16,6 +16,7 @@ exports.assertDirectoriesAreEqual = assertDirectoriesAreEqual;
 exports.assertFilesAreEqual = assertFilesAreEqual;
 exports.assertIncludes = assertIncludes;
 exports.atomicWriteFileSync = atomicWriteFileSync;
+exports.syncFile = syncFile;
 exports.getFileNamesAndRemoveOutput = getFileNamesAndRemoveOutput;
 
 function normaliseError(error) {
@@ -232,3 +233,10 @@ function atomicWriteFileSync(filePath, contents) {
 	fs.writeFileSync(stagingPath, contents);
 	fs.renameSync(stagingPath, filePath);
 }
+
+// It appears that on MacOS, it sometimes takes long for the file system to update
+function syncFile(filePath) {
+	const file = fs.openSync(filePath);
+	fs.fsyncSync(file);
+	fs.closeSync(file);
+}