feat: add importOverrides as a variant of componentImports

projects/testing-library/src/lib/models.ts

@@ -1,17 +1,17 @@
 import {
-  Type,
+  Binding,
   DebugElement,
-  ModuleWithProviders,
-  EventEmitter,
   EnvironmentProviders,
+  EventEmitter,
+  InputSignalWithTransform,
+  ModuleWithProviders,
   Provider,
   Signal,
-  InputSignalWithTransform,
-  Binding,
+  Type,
 } from '@angular/core';
 import { ComponentFixture, DeferBlockBehavior, DeferBlockState, TestBed } from '@angular/core/testing';
 import { Routes } from '@angular/router';
-import { BoundFunctions, Queries, queries, Config as dtlConfig, PrettyDOMOptions } from '@testing-library/dom';
+import { BoundFunctions, Config as dtlConfig, PrettyDOMOptions, Queries, queries } from '@testing-library/dom';
 
 // TODO: import from Angular (is a breaking change)
 interface OutputRef<T> {
@@ -381,6 +381,24 @@ export interface RenderComponentOptions<ComponentType, Q extends Queries = typeo
    * })
    */
   componentImports?: (Type<unknown> | unknown[])[];
+  /**
+   * @description
+   * Replace specific imports on a standalone component without replacing the entire imports array.
+   * Unlike `componentImports`, which replaces all imports, this option lets you swap out targeted
+   * child components without needing to enumerate all other imports.
+   * Mutually exclusive with `componentImports`.
+   *
+   * @default
+   * undefined
+   *
+   * @example
+   * await render(AppComponent, {
+   *   importOverrides: [
+   *     { replace: RealChildComponent, with: MockChildComponent }
+   *   ]
+   * })
+   */
+  importOverrides?: ImportOverride[];
   /**
    * @description
    * Queries to bind. Overrides the default set from DOM Testing Library unless merged.
@@ -492,6 +510,13 @@ export interface RenderComponentOptions<ComponentType, Q extends Queries = typeo
   deferBlockBehavior?: DeferBlockBehavior;
 }
 
+export interface ImportOverride {
+  /** The import to replace (matched by identity) */
+  replace: Type<unknown>;
+  /** The replacement import to use instead */
+  with: Type<unknown> | unknown[];
+}
+
 export interface ComponentOverride<T> {
   component: Type<T>;
   providers: Provider[];

projects/testing-library/src/lib/testing-library.ts

@@ -1,5 +1,7 @@
 import {
   ApplicationInitStatus,
+  ApplicationRef,
+  Binding,
   ChangeDetectorRef,
   Component,
   NgZone,
@@ -11,8 +13,6 @@ import {
   SimpleChanges,
   Type,
   isStandalone,
-  Binding,
-  ApplicationRef,
 } from '@angular/core';
 import { ComponentFixture, DeferBlockBehavior, DeferBlockState, TestBed, tick } from '@angular/core/testing';
 import { NavigationExtras, Router } from '@angular/router';
@@ -32,11 +32,12 @@ import {
 import { getConfig } from './config';
 import {
   ComponentOverride,
+  Config,
+  ImportOverride,
   OutputRefKeysWithCallback,
   RenderComponentOptions,
   RenderResult,
   RenderTemplateOptions,
-  Config,
 } from './models';
 
 type SubscribedOutput<T> = readonly [key: keyof T, callback: (v: any) => void, subscription: OutputRefSubscription];
@@ -75,6 +76,7 @@ export async function render<SutType, WrapperType = SutType>(
     componentProviders = [],
     childComponentOverrides = [],
     componentImports,
+    importOverrides,
     excludeComponentDeclaration = false,
     routes = [],
     removeAngularAttributes = false,
@@ -100,6 +102,12 @@ export async function render<SutType, WrapperType = SutType>(
     ...domConfig,
   });
 
+  if (componentImports && importOverrides) {
+    throw new Error(
+      `Cannot specify both componentImports and importOverrides. Use componentImports for full replacement, or importOverrides for targeted replacement.`,
+    );
+  }
+
   TestBed.configureTestingModule({
     declarations: addAutoDeclarations(sut, {
       declarations,
@@ -115,6 +123,7 @@ export async function render<SutType, WrapperType = SutType>(
     deferBlockBehavior: deferBlockBehavior ?? DeferBlockBehavior.Manual,
   });
   overrideComponentImports(sut, componentImports);
+  applyImportOverrides(sut, importOverrides);
   overrideChildComponentProviders(childComponentOverrides);
 
   configureTestBed(TestBed);
@@ -462,6 +471,21 @@ function overrideComponentImports<SutType>(sut: Type<SutType> | string, imports:
   }
 }
 
+function applyImportOverrides<SutType>(sut: Type<SutType> | string, overrides: ImportOverride[] | undefined) {
+  if (overrides?.length) {
+    if (typeof sut === 'function' && isStandalone(sut)) {
+      TestBed.overrideComponent(sut, {
+        remove: { imports: overrides.map((o) => o.replace) },
+        add: { imports: overrides.map((o) => o.with) },
+      });
+    } else {
+      throw new Error(
+        `Error while rendering ${sut}: Cannot specify importOverrides on a template or non-standalone component.`,
+      );
+    }
+  }
+}
+
 function overrideChildComponentProviders(componentOverrides: ComponentOverride<any>[]) {
   if (componentOverrides) {
     for (const { component, providers } of componentOverrides) {

projects/testing-library/src/tests/import-overrides.spec.ts

@@ -0,0 +1,86 @@
+import { Component } from '@angular/core';
+import { expect, test } from 'vitest';
+import { render, screen } from '../public_api';
+
+@Component({
+  selector: 'atl-child',
+  template: `Hello from child`,
+  standalone: true,
+})
+class ChildComponent {}
+
+@Component({
+  selector: 'atl-child',
+  template: `Hello from stub`,
+  standalone: true,
+  host: { 'collision-id': 'StubComponent' },
+})
+class StubChildComponent {}
+
+@Component({
+  selector: 'atl-other',
+  template: `Hello from other`,
+  standalone: true,
+})
+class OtherComponent {}
+
+@Component({
+  selector: 'atl-fixture',
+  template: `<atl-child /><atl-other />`,
+  standalone: true,
+  imports: [ChildComponent, OtherComponent],
+})
+class FixtureComponent {}
+
+@Component({
+  selector: 'atl-non-standalone',
+  template: `non-standalone`,
+  standalone: false,
+})
+class NonStandaloneComponent {}
+
+test('importOverrides - replaces a single import', async () => {
+  await render(FixtureComponent, {
+    importOverrides: [{ replace: ChildComponent, with: StubChildComponent }],
+  });
+
+  expect(screen.getByText('Hello from stub')).toBeInTheDocument();
+  expect(screen.queryByText('Hello from child')).not.toBeInTheDocument();
+});
+
+test('importOverrides - leaves other imports intact', async () => {
+  await render(FixtureComponent, {
+    importOverrides: [{ replace: ChildComponent, with: StubChildComponent }],
+  });
+
+  expect(screen.getByText('Hello from stub')).toBeInTheDocument();
+  expect(screen.getByText('Hello from other')).toBeInTheDocument();
+});
+
+test('importOverrides - throws on non-standalone component', async () => {
+  await expect(
+    render(NonStandaloneComponent, {
+      declarations: [NonStandaloneComponent],
+      excludeComponentDeclaration: true,
+      importOverrides: [{ replace: ChildComponent, with: StubChildComponent }],
+    } as any),
+  ).rejects.toThrow(/Cannot specify importOverrides on a template or non-standalone component/);
+});
+
+test('importOverrides - throws when used with componentImports', async () => {
+  await expect(
+    render(FixtureComponent, {
+      componentImports: [ChildComponent],
+      importOverrides: [{ replace: ChildComponent, with: StubChildComponent }],
+    }),
+  ).rejects.toThrow(/Cannot specify both componentImports and importOverrides/);
+});
+
+test('importOverrides - empty array is a no-op', async () => {
+  await render(FixtureComponent, {
+    importOverrides: [],
+  });
+
+  expect(screen.getByText('Hello from child')).toBeInTheDocument();
+  expect(screen.getByText('Hello from other')).toBeInTheDocument();
+});