diff --git a/tests/test_builtin.js b/tests/test_builtin.js
index f547037..1de89ed 100644
--- a/tests/test_builtin.js
+++ b/tests/test_builtin.js
@@ -381,11 +381,9 @@ function test_number()
     assert(Number.isNaN(Number("-")));
     assert(Number.isNaN(Number("\x00a")));
 
-    // TODO: Fix rounding errors on Windows/Cygwin.
-    if (typeof os !== 'undefined' && ['win32', 'cygwin'].includes(os.platform)) {
-        return;
-    }
-
+    assert((1-2**-53).toString(12), "0.bbbbbbbbbbbbbba");
+    assert((1000000000000000128).toString(), "1000000000000000100");
+    assert((1000000000000000128).toFixed(0), "1000000000000000128");
     assert((25).toExponential(0), "3e+1");
     assert((-25).toExponential(0), "-3e+1");
     assert((2.5).toPrecision(1), "3");
@@ -393,6 +391,8 @@ function test_number()
     assert((25).toPrecision(1) === "3e+1");
     assert((1.125).toFixed(2), "1.13");
     assert((-1.125).toFixed(2), "-1.13");
+    assert((0.5).toFixed(0), "1");
+    assert((-0.5).toFixed(0), "-1");
 
     assert((1.3).toString(7), "1.2046204620462046205");
     assert((1.3).toString(35), "1.ahhhhhhhhhm");