diff --git a/Makefile b/Makefile
index ba101d56..c174ec26 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,7 @@ test: ## Run the pure-PHP test suites
 	php tests/RevisionOverridesTest.php
 	php tests/IgnoreHtmlClassTest.php
 	php tests/JsDefaultsTest.php
+	php tests/MacrosTest.php
 
 phpcs: vendor/autoload.php ## parallel-lint + minus-x + phpcs against the MediaWiki coding standard
 	composer test
diff --git a/extension.json b/extension.json
index 77734fc4..9eced455 100644
--- a/extension.json
+++ b/extension.json
@@ -1,6 +1,6 @@
 {
 	"name": "SimpleMathJax",
-	"version": "1.2.0",
+	"version": "1.2.1",
 	"author": "jmnote",
 	"url": "https://www.mediawiki.org/wiki/Extension:SimpleMathJax",
 	"description": "render TeX between <code><nowiki><math></nowiki></code> and <code><nowiki></math></nowiki></code>",
diff --git a/tests/MacrosTest.php b/tests/MacrosTest.php
new file mode 100644
index 00000000..60dd2284
--- /dev/null
+++ b/tests/MacrosTest.php
@@ -0,0 +1,52 @@
+<?php
+// Ensure ext.SimpleMathJax.js macros are syntactically valid and balanced.
+
+$failures = 0;
+
+function assert_same( $name, $expected, $actual ) {
+	global $failures;
+	if ( $expected === $actual ) {
+		echo "ok   $name\n";
+		return;
+	}
+	$failures++;
+	echo "FAIL $name\n";
+	echo '  expected: ' . var_export( $expected, true ) . "\n";
+	echo '  actual:   ' . var_export( $actual, true ) . "\n";
+}
+
+$js = file_get_contents( __DIR__ . '/../resources/ext.SimpleMathJax.js' );
+
+if ( !preg_match( '/macros:\s*(\{.*?\n\s{6}\})/s', $js, $m ) ) {
+	echo "FAIL macros object not found in ext.SimpleMathJax.js\n";
+	exit( 1 );
+}
+
+$lines = explode( "\n", $m[1] );
+$macros = [];
+foreach ( $lines as $line ) {
+	if ( preg_match( '/^\s*([A-Za-z0-9_]+):\s*(.+?),?\s*$/', $line, $lm ) ) {
+		$k = $lm[1];
+		$v = trim( $lm[2] );
+		$macros[$k] = $v;
+	}
+}
+
+assert_same( 'macros parsed', true, count( $macros ) > 0 );
+
+// Verify PR #87 fixes
+assert_same( 'Bbb macro does not wrap in outer group', '"\\\\mathbb"', $macros['Bbb'] ?? null );
+assert_same( 'bold macro does not wrap in outer group', '"\\\\mathbf"', $macros['bold'] ?? null );
+assert_same( 'vline macro has valid smash lvert syntax', '"{\\\\smash{\\\\large\\\\lvert}}"', $macros['vline'] ?? null );
+
+// All macros have balanced braces
+$unbalanced = [];
+foreach ( $macros as $name => $def ) {
+	if ( substr_count( $def, '{' ) !== substr_count( $def, '}' ) ) {
+		$unbalanced[] = "$name: $def";
+	}
+}
+assert_same( 'all macros have balanced braces', [], $unbalanced );
+
+echo $failures === 0 ? "\nAll tests passed.\n" : "\n$failures test(s) FAILED.\n";
+exit( $failures === 0 ? 0 : 1 );