Fix ECMA 262 \Z and \z tests

The old test was incorrect because "\Z" is actually valid. It matches a
literal Z in ECMA 262.

Author: ssilverman

tests/draft2019-09/optional/ecmascript-regex.json

@@ -4,12 +4,50 @@
         "schema": { "format": "regex" },
         "tests": [
             {
-                "description": "ECMA 262 has no support for \\Z anchor from .NET",
+                "description": "ECMA 262 has no support for \\Z anchor",
                 "data": "^\\S(|(.|\\n)*\\S)\\Z",
                 "valid": false
             }
         ]
     },
+    {
+        "description": "ECMA 262 regex non-compliance",
+        "schema": {
+            "type": "string",
+            "pattern": "^x\\Z"
+        },
+        "tests": [
+            {
+                "description": "\\Z should match literal Z",
+                "data": "xZ",
+                "valid": true
+            },
+            {
+                "description": "\\Z should not match end",
+                "data": "x",
+                "valid": false
+            }
+        ]
+    },
+    {
+        "description": "ECMA 262 regex non-compliance",
+        "schema": {
+            "type": "string",
+            "pattern": "^x\\z"
+        },
+        "tests": [
+            {
+                "description": "\\z should match literal z",
+                "data": "xz",
+                "valid": true
+            },
+            {
+                "description": "\\z should not match end",
+                "data": "x",
+                "valid": false
+            }
+        ]
+    },
     {
         "description": "ECMA 262 regex $ does not match trailing newline",
         "schema": {