feat(test): add --shuffle flag to randomize test ordering (#11163)

1 files changed, 19 insertions, 0 deletions

diff --git a/runtime/js/40_testing.js b/runtime/js/40_testing.js
index 0106f895a..4ee863ee7 100644
--- a/runtime/js/40_testing.js
+++ b/runtime/js/40_testing.js
@@ -217,6 +217,7 @@ finishing test case.`;
   async function runTests({
     disableLog = false,
     filter = null,
+    shuffle = null,
   } = {}) {
     const originalConsole = globalThis.console;
     if (disableLog) {
@@ -234,6 +235,24 @@ finishing test case.`;
       only: only.length > 0,
     });
 
+    if (shuffle !== null) {
+      // http://en.wikipedia.org/wiki/Linear_congruential_generator
+      const nextInt = (function (state) {
+        const m = 0x80000000;
+        const a = 1103515245;
+        const c = 12345;
+
+        return function (max) {
+          return state = ((a * state + c) % m) % max;
+        };
+      }(shuffle));
+
+      for (let i = pending.length - 1; i > 0; i--) {
+        const j = nextInt(i);
+        [pending[i], pending[j]] = [pending[j], pending[i]];
+      }
+    }
+
     for (const test of pending) {
       const {
         name,