Farenheith/strict-mocha-describers

import { TestFunction } from 'mocha';
import { testUtils } from './test-utils';
import { StaticMethodSuite } from './types/static-method-suite';
import { backupHelper } from './backup-helper';

export class StaticMethodDescribeHelper<Class> {
  constructor(protected readonly cls: Class) {}

  private createSingleStaticDescribe = (
    suite: (title: string, fn: () => void) => void,
  ) => {
    return (method: keyof Class, fn: (it: TestFunction) => void) => {
      suite(`Static method ${method}`, () => {
        const wrapper = {} as {
          backup: Array<[keyof Class, Class[keyof Class]]>;
        };
        beforeEach(this.getBeforeEach(wrapper, method));
        fn(it);
        afterEach(this.getAfterEach(wrapper));
      });
    };
  };

  private getBeforeEach(
    wrapper: {
      backup: Array<[keyof Class, Class[keyof Class]]>;
    },
    method: keyof Class,
  ): Mocha.Func {
    return () => {
      wrapper.backup = testUtils.prepare(this.cls, this.cls, method);
    };
  }

  private getAfterEach(wrapper: {
    backup: Array<[keyof Class, Class[keyof Class]]>;
  }): Mocha.Func {
    return () => {
      backupHelper.restore(this.cls, wrapper.backup);
    };
  }

  createStaticDescribe() {
    return testUtils.setupFunction(
      this.createSingleStaticDescribe,
      describe,
    ) as StaticMethodSuite<Class>;
  }
}