diff --git a/bin/packages/watch.js b/bin/packages/watch.js
index fce8a6beedb977..dcbacb81d671e3 100644
--- a/bin/packages/watch.js
+++ b/bin/packages/watch.js
@@ -23,9 +23,11 @@ const exists = ( filename ) => {
 	return false;
 };
 
-// Exclude deceitful source-like files, such as editor swap files.
+// Exclude test files including .js files inside of __tests__ or test folders
+// and files with a suffix of .test or .spec (e.g. blocks.test.js),
+// and deceitful source-like files, such as editor swap files.
 const isSourceFile = ( filename ) => {
-	return /.\.(js|scss)$/.test( filename );
+	return ! [ /\/(__tests__|test)\/.+.js$/, /.\.(spec|test)\.js$/ ].some( ( regex ) => regex.test( filename ) ) && /.\.(js|scss)$/.test( filename );
 };
 
 const rebuild = ( filename ) => filesToBuild.set( filename, true );