test: add staging cases

checker/specification/staging.md

@@ -1,3 +1,49 @@
 Currently implementing:
 
 > This file is for work-in-progress and can help separating features that are being implemented to regressions
+
+### Feats
+
+#### `Object.freeze`
+
+> When `Object.freeze` is called, the object's `isSealed` is inferred as `true`
+
+```ts
+const obj = {}
+let result = Object.freeze(obj);
+(obj === result) satisfies true;
+obj.property = 2;
+Object.isSealed(obj) satisfies true;
+```
+
+- Cannot write to property 'property'
+
+#### `Object.seal`
+
+> When `Object.seal` is called, the object's `isFrozen` and `isSealed` are inferred as `true`
+
+```ts
+const obj = {}
+let result = Object.seal(obj);
+(obj === result) satisfies true;
+obj.property = 2;
+Object.isFrozen(obj) satisfies true;
+Object.isSealed(obj) satisfies true;
+```
+
+- Cannot write to property 'property'
+
+#### `Object.preventExtensions`
+
+> When `Object.preventExtensions` is called, the object's `isFrozen` and `isSealed` are inferred as `true`
+
+```ts
+const obj = {}
+let result = Object.preventExtensions(obj);
+(obj === result) satisfies true;
+obj.property = 2;
+Object.isFrozen(obj) satisfies true;
+Object.isSealed(obj) satisfies true;
+```
+
+- Cannot write to property 'property'