From 70d9781bf23843a8afa1fa507c8038520c527e50 Mon Sep 17 00:00:00 2001
From: satanTime <m@sudo.eu>
Date: Sat, 10 Dec 2022 14:30:00 +0100
Subject: [PATCH] feat(MockInstance): ignores undefined properties #4367

---
 .../src/lib/mock-helper/mock-helper.stub.ts   |   3 +
 tests/issue-4367/test.spec.ts                 | 125 ++++++++++++++++++
 2 files changed, 128 insertions(+)
 create mode 100644 tests/issue-4367/test.spec.ts

diff --git a/libs/ng-mocks/src/lib/mock-helper/mock-helper.stub.ts b/libs/ng-mocks/src/lib/mock-helper/mock-helper.stub.ts
index ff3ca93992..bcc7faadd2 100644
--- a/libs/ng-mocks/src/lib/mock-helper/mock-helper.stub.ts
+++ b/libs/ng-mocks/src/lib/mock-helper/mock-helper.stub.ts
@@ -19,6 +19,9 @@ export default <T = MockedFunction>(instance: any, override: any, style?: 'get'
 
   for (const key of Object.getOwnPropertyNames(applyOverrides)) {
     const desc = skipProps.indexOf(key) === -1 ? Object.getOwnPropertyDescriptor(applyOverrides, key) : undefined;
+    if (desc && Object.prototype.hasOwnProperty.call(desc, 'value') && desc.value === undefined) {
+      continue;
+    }
     helperMockService.definePropertyDescriptor(correctInstance, key, desc);
   }
 
diff --git a/tests/issue-4367/test.spec.ts b/tests/issue-4367/test.spec.ts
new file mode 100644
index 0000000000..6569e9a5cd
--- /dev/null
+++ b/tests/issue-4367/test.spec.ts
@@ -0,0 +1,125 @@
+import { Component, Injectable, NgModule } from '@angular/core';
+import { TestBed } from '@angular/core/testing';
+
+import {
+  MockBuilder,
+  MockInstance,
+  MockProvider,
+  MockRender,
+} from 'ng-mocks';
+
+@Injectable()
+class TargetService {
+  public method1() {
+    return `${this.constructor.name}:method1:real`;
+  }
+
+  public method2() {
+    return `${this.constructor.name}:method2:real`;
+  }
+}
+
+@Component({
+  selector: 'target',
+  template: '',
+})
+class TargetComponent {
+  constructor(public readonly service: TargetService) {}
+}
+
+@NgModule({
+  declarations: [TargetComponent],
+  exports: [TargetComponent],
+  providers: [TargetService],
+})
+class TargetModule {}
+
+// @see https://github.com/help-me-mom/ng-mocks/issues/4367
+describe('issue-4367', () => {
+  describe('MockProvider', () => {
+    beforeEach(() =>
+      TestBed.configureTestingModule({
+        declarations: [TargetComponent],
+        providers: [
+          MockProvider(TargetService, {
+            method1: () => 'mock',
+            method2: undefined, // <- should be default spy
+          }),
+        ],
+      }),
+    );
+
+    it('overrides method1 only', () => {
+      const fixture = MockRender(TargetComponent);
+
+      // method2 should be default mock
+      expect(
+        fixture.point.componentInstance.service.method1,
+      ).toBeDefined();
+      expect(
+        fixture.point.componentInstance.service.method2,
+      ).toBeDefined();
+    });
+  });
+
+  describe('MockBuilder', () => {
+    beforeEach(() =>
+      MockBuilder(TargetComponent, TargetModule).mock(TargetService, {
+        method1: () => 'mock',
+        method2: undefined, // <- should be default spy
+      }),
+    );
+
+    it('overrides method1 only', () => {
+      const fixture = MockRender(TargetComponent);
+
+      // method2 should be default mock
+      expect(
+        fixture.point.componentInstance.service.method1,
+      ).toBeDefined();
+      expect(
+        fixture.point.componentInstance.service.method2,
+      ).toBeDefined();
+    });
+  });
+
+  describe('MockInstance', () => {
+    MockInstance.scope();
+    beforeEach(() =>
+      TestBed.configureTestingModule({
+        declarations: [TargetComponent],
+        providers: [MockProvider(TargetService)],
+      }),
+    );
+
+    it('overrides method1 only', () => {
+      MockInstance(TargetService, () => ({
+        method1: () => 'mock',
+        method2: undefined, // <- should be default spy
+      }));
+      const fixture = MockRender(TargetComponent);
+
+      // method2 should be default mock
+      expect(
+        fixture.point.componentInstance.service.method1,
+      ).toBeDefined();
+      expect(
+        fixture.point.componentInstance.service.method2,
+      ).toBeDefined();
+    });
+
+    it('overrides method1 and method2', () => {
+      MockInstance(TargetService, 'method1', () => 'mock');
+      MockInstance(TargetService, 'method2', undefined as never); // <- breaks the things
+      const fixture = MockRender(TargetComponent);
+
+      // method2 should be undefined
+      expect(
+        fixture.point.componentInstance.service.method1,
+      ).toBeDefined();
+      expect(
+        fixture.point.componentInstance.service.method2,
+      ).not.toBeDefined();
+    });
+  });
+});