我创建了一个 Angular 指令，它使用 CSS 选择器自动 trim 我的应用程序中的输入，它看起来像这样......

import { Directive, HostListener, forwardRef } from '@angular/core';
import { DefaultValueAccessor, NG_VALUE_ACCESSOR } from '@angular/forms';

export const TRIM_VALUE_ACCESSOR: any = {
  provide: NG_VALUE_ACCESSOR,
  useExisting: forwardRef(() => TrimInputDirective),
  multi: true
};

/**
 * The trim accessor for writing trimmed value and listening to changes that is
 * used by the {@link NgModel}, {@link FormControlDirective}, and
 * {@link FormControlName} directives.
 */
/* tslint:disable */
@Directive({
  selector: `
    input
    :not([type=checkbox])
    :not([type=radio])
    :not([type=password])
    :not([readonly])
    :not(.ng-trim-ignore)
    [formControlName],

    input
    :not([type=checkbox])
    :not([type=radio])
    :not([type=password])
    :not([readonly])
    :not(.ng-trim-ignore)
    [formControl],

    input
    :not([type=checkbox])
    :not([type=radio])
    :not([type=password])
    :not([readonly])
    :not(.ng-trim-ignore)
    [ngModel],

    textarea
    :not([readonly])
    :not(.ng-trim-ignore)
    [formControlName],

    textarea
    :not([readonly])
    :not(.ng-trim-ignore)
    [formControl],

    textarea
    :not([readonly])
    :not(.ng-trim-ignore)[ngModel],
    :not([readonly])
    :not(.ng-trim-ignore)
    [ngDefaultControl]'
  `,
  providers: [ TRIM_VALUE_ACCESSOR ]
})
/* tslint:enable */
export class TrimInputDirective extends DefaultValueAccessor {

  protected _onTouched: any;

  /**
   * ngOnChange - Lifecycle hook that is called when any data-bound property of a directive changes.
   * @param {string} val - trim value onChange.
   */
  @HostListener('input', ['$event.target.value'])
  public ngOnChange = (val: string) => {
    this.onChange(val.trim());
  }

  /**
   * applyTrim - trims the passed value
   * @param {string} val - passed value.
   */
  @HostListener('blur', ['$event.target.value'])
  public applyTrim(val: string) {
    this.writeValue(val.trim());
    this._onTouched();
  }

  /**
   * writeValue - trims the passed value
   * @param {any} value - passed  value.
   */
  public writeValue(value: any): void {
    if (typeof value === 'string') {
      value = value.trim();
    }

    super.writeValue(value);
  }

  /**
   * registerOnTouched Registers a callback function that should be called when the control receives a blur event.
   * @param {function} fn - The user information.
   */
  public registerOnTouched(fn: any): void {
    this._onTouched = fn;
  }
}

现在作为一名优秀的开发人员，我必须正确进行一些单元测试......所以我开始将文件放在一起，就在这里

import {Component} from '@angular/core';
import {async, ComponentFixture, TestBed} from '@angular/core/testing';
import {By} from '@angular/platform-browser';
import {TrimInputDirective} from './trim-input.directive';

import {expect} from 'chai';

@Component({
  selector: 'my-directive-test-component',
  template: ''
})
class TestComponent {
}

describe('Trim Directive', () => {
  let fixture: ComponentFixture<TestComponent>;
  let inputDebugElement: any;
  let directive: TrimInputDirective;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [
        TestComponent,
        TrimInputDirective
      ],
      providers: []
    }).overrideComponent(TestComponent, {
      set: {
        template: '<input type="text">'
      }
    }).compileComponents().then(() => {
      fixture = TestBed.createComponent(TestComponent);
      fixture.detectChanges();
      inputDebugElement = fixture.debugElement.query(By.css('input'));
      directive = inputDebugElement.injector.get(TrimInputDirective);
    });
  }));

  it('should trim the input', () => {
    directive.ngOnChange('     1234.56     ')
    expect('1234.56').to.be('1234.56'); // I know this isn't the correct test... I will amend this
  });
});

现在我想运行我的测试以确保规范文件中的设置正确，但我收到以下错误:

HeadlessChrome 0.0.0 (Mac OS X 10.12.6) Trim Directive "before each" hook for "should trim the input" FAILED Uncaught (in promise): Error: StaticInjectorError(DynamicTestModule)[TrimInputDirective]:
StaticInjectorError(Platform: core)[TrimInputDirective]: NullInjectorError: No provider for TrimInputDirective! Error: StaticInjectorError(DynamicTestModule)[TrimInputDirective]:

我不明白为什么会出现这个错误，为什么我必须提供指令？我不认为这是必要的，如果我必须提供我提供什么？提供实际指令不起作用/解决错误？我很困扰。如果有人能告诉我如何解决这个问题或者我为什么会遇到这个问题，我将不胜感激。

请注意，这是一个遗留的 Angular 应用程序，是在 AngularCLI 可用。所以它有点不正统(例如它没有使用 Jasmin)。

最佳答案

1) 你不需要提供你的指令，你只需要在 TestingModule 中声明它。然后，它将与相应的选择器一起用在模板中。

2) 您的选择器与您输入的选择器不一致。如果您希望它应用于特定类型的所有输入或更改您的测试，请移除 formControlName。

input
    :not([type=checkbox])
    :not([type=radio])
    :not([type=password])
    :not([readonly])
    :not(.ng-trim-ignore)
    [formControlName],
    ^^^^^^^^^^^^^^^^^^ 

3) 指令在某些事件上被触发。您需要模拟这些事件才能看到效果。看看这个简化的例子。 ( Stackblitz )

@Directive({
  selector: `
    input
    :not([type=checkbox])
    :not([type=radio])
    :not([type=password])
    :not([readonly])
    :not(.ng-trim-ignore)
  `
})
export class TrimInputDirective {
  constructor(private el: ElementRef) { }

  @HostListener('blur') onLeave() {
   if (this.el.nativeElement.value)
    this.el.nativeElement.value = this.el.nativeElement.value.trim();
  }

}

和测试:

describe('Trim Directive', () => {
  let fixture: ComponentFixture<TestComponent>;
  let inputDebugElement: any;
  let directive: TrimInputDirective;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [
        TestComponent,
        TrimInputDirective
      ],
      imports: [FormsModule],
      providers: []
    }).overrideComponent(TestComponent, {
      set: {
        template: '<input type="text">'
      }
    }).compileComponents().then(() => {
      fixture = TestBed.createComponent(TestComponent);
      inputDebugElement = fixture.debugElement.query(By.css('input')).nativeElement;
                                                                      ^^^^^^^^^^^^
    }); 
  }));

  it('should trim the input', () => {
    inputDebugElement.value = '     1234.56     ';
    inputDebugElement.dispatchEvent(new Event('blur'));
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    fixture.detectChanges();
    expect(inputDebugElement.value).toBe('1234.56'); 
  });
});

关于javascript - Angular Testing 错误 - NullInjectorError : No provider for TrimInputDirective，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50639569/