message: API: Use IUnitModel in FixtureUtils where applicable
diff: @@ -2,7 +2,7 @@ import {User} from '../src/models/User';
  import {Course, ICourseModel} from '../src/models/Course';
  import {IUserModel} from '../src/models/User';
  import {Lecture} from '../src/models/Lecture';
  -import {Unit} from '../src/models/units/Unit';
  +import {Unit, IUnitModel} from '../src/models/units/Unit';
  import {ICourse} from '../../shared/models/ICourse';
  import {ILecture} from '../../shared/models/ILecture';
  import {IUnit} from '../../shared/models/units/IUnit';
  @@ -139,9 +139,9 @@ export class FixtureUtils {
  return Lecture.findOne({units: { $in: [ unit._id ] }});
  }
  - public static async getRandomUnit(hash?: string): Promise<IUnit> {
  + public static async getRandomUnit(hash?: string): Promise<IUnitModel> {
  const array = await this.getUnits();
  - return this.getRandom<IUnit>(array, hash);
  + return this.getRandom<IUnitModel>(array, hash);
  }
  public static async getRandomUnitFromLecture(lecture: ILecture, hash?: string): Promise<IUnit> {
  @@ -149,9 +149,9 @@ export class FixtureUtils {
  return Unit.findById(unitId);
  }
  - public static async getRandomUnitFromCourse(course: ICourse, hash?: string): Promise<IUnit> {
  + public static async getRandomUnitFromCourse(course: ICourse, hash?: string): Promise<IUnitModel> {
  const units = await Unit.find({_course: course});
  - return await this.getRandom<IUnit>(units, hash);
  + return await this.getRandom<IUnitModel>(units, hash);
  }
  /**
  @@ -193,7 +193,7 @@ export class FixtureUtils {
  return Lecture.find();
  }
  - public static async getUnits(): Promise<IUnit[]> {
  + public static async getUnits(): Promise<IUnitModel[]> {
  return Unit.find();
  }
  