Add test to detect faulty behaviour

Author: Luca Forstner

packages/utils/test/object.test.ts

@@ -200,7 +200,7 @@ describe('dropUndefinedKeys()', () => {
     });
   });
 
-  test('objects with circular reference', () => {
+  test('should not throw on objects with circular reference', () => {
     const dog: any = {
       food: undefined,
     };
@@ -217,11 +217,25 @@ describe('dropUndefinedKeys()', () => {
 
     dog.chases = rat;
 
-    expect(dropUndefinedKeys(human)).toStrictEqual({
-      pets: {
-        chases: rat,
-      },
-    });
+    const result = dropUndefinedKeys(human);
+
+    // Removes undefined keys
+    expect(Object.keys(result)).toEqual(['pets']);
+    expect(Object.keys(result.pets)).toEqual(['chases']);
+    expect(Object.keys(result.pets.chases)).toEqual(['scares', 'weight']);
+
+    // Returns new object
+    expect(human === result).toBe(false);
+    expect(dog === result.pets).toBe(false);
+    expect(rat === result.pets.chases).toBe(false);
+
+    // Returns new references within objects
+    expect(human === result.pets.chases.scares).toBe(false);
+    expect(dog === result.pets.chases.scares.pets).toBe(false);
+    expect(rat === result.pets.chases.scares.pets.chases).toBe(false);
+
+    // Keeps circular reference
+    expect(result.pets.chases.scares === result).toBe(true);
   });
 
   test('arrays with circular reference', () => {
@@ -235,10 +249,22 @@ describe('dropUndefinedKeys()', () => {
 
     egg[0] = chicken;
 
-    expect(dropUndefinedKeys(chicken)).toStrictEqual({
-      lays: egg,
-      weight: '1kg',
-    });
+    const result = dropUndefinedKeys(chicken);
+
+    // Removes undefined keys
+    expect(Object.keys(result)).toEqual(['weight', 'lays']);
+    expect(Object.keys(result.lays)).toEqual(['0']);
+
+    // Returns new objects
+    expect(chicken === result).toBe(false);
+    expect(egg === result.lays).toBe(false);
+
+    // Returns new references within objects
+    expect(chicken === result.lays[0]).toBe(false);
+    expect(egg === result.lays[0].lays).toBe(false);
+
+    // Keeps circular reference
+    expect(result.lays[0] === result).toBe(true);
   });
 });