added tests for helper classes and modified previous tests

Diligent.WebAPI.Business/Helper/StringGenerator.cs

                 RequireUppercase = true
             };
 
+            if(opts.RequiredLength < 4)
+                opts.RequiredLength = 4;
+
             string[] randomChars = new[] {
                 "ABCDEFGHJKLMNOPQRSTUVWXYZ",    // uppercase
                 "abcdefghijkmnopqrstuvwxyz",    // lowercase

Diligent.WebAPI.Tests/Controllers/UsersControllerTest.cs

 using Diligent.WebAPI.Business.MappingProfiles;
 using Diligent.WebAPI.Contracts.DTOs;
 using Diligent.WebAPI.Contracts.DTOs.User;
+using Diligent.WebAPI.Contracts.Exceptions;
 using Diligent.WebAPI.Data.Entities;
 
 namespace Diligent.WebAPI.Tests.Controllers
         [Fact]
         public async Task GetUserById_ShouldReturn404_WhenUserDoesNotExist()
         {
-            _userService.GetById(Arg.Any<int>()).Returns<User>(x => null);
-            UsersController usersController = new(_userService, _mapper);
+            _userService.When(x => x.GetById(Arg.Any<int>()))
+                .Do(x => { throw new EntityNotFoundException(); });
 
-            var result = await usersController.GetUser(1);
+            UsersController usersController = new(_userService, _mapper);
 
-            (result as ObjectResult).StatusCode.Should().Be(400);
+            await Assert.ThrowsAsync<EntityNotFoundException>(() => usersController.GetUser(15));
         }
 
         [Fact]
         [Fact]
         public async Task DeleteUser_ShouldReturn400_WhenUserDoesNotExist()
         {
-            _userService.GetById(Arg.Any<int>()).Returns<User>(x => null);
-            UsersController usersController = new(_userService, _mapper);
+            _userService.When(x => x.GetById(Arg.Any<int>()))
+                .Do(x => { throw new EntityNotFoundException(); });
 
-            var result = await usersController.DeleteUser(1);
+            UsersController usersController = new(_userService, _mapper);
 
-            (result as ObjectResult).StatusCode.Should().Be(400);
+            await Assert.ThrowsAsync<EntityNotFoundException>(() => usersController.DeleteUser(15));
         }
     }
 }

Diligent.WebAPI.Tests/Helpers/HTMLHelperTests.cs

+using Diligent.WebAPI.Business.Helper;
+
+namespace Diligent.WebAPI.Tests.Helpers
+{
+    public class HTMLHelperTests
+    {
+        [Fact]
+        public void RenderForgotPasswordPage_ShouldReturnRawHTML_WithMailAsHref()
+        {
+            string url = "test.user@dilig.net";
+            Assert.Contains($"href=\"{url}\">", HTMLHelper.RenderForgotPasswordPage(url));
+        }
+
+        [Fact]
+        public void RenderRegisterPage_ShouldReturnRawHTML_WithMailAsHref()
+        {
+            string url = "test.user@dilig.net";
+            Assert.Contains($"href=\"{url}\">", HTMLHelper.RenderRegisterPage(url));
+        }
+
+        [Fact]
+        public void RenderTagPage_ShouldReturnRawHTML_WithMailAsHref()
+        {
+            string url = "test.user@dilig.net";
+            Assert.Contains($"href=\"{url}\">", HTMLHelper.RenderTagPage(url));
+        }
+
+        [Fact]
+        public void SuccessfulStep_ShouldReturnRawHTML_WithMailAsHref()
+        {
+            Assert.Contains($"<p style=\"color: #017397;\">message date</p>" , HTMLHelper.SuccessfulStep("message", "pattern", "date"));
+        }
+    }
+}

Diligent.WebAPI.Tests/Helpers/StringGeneratorTests.cs

+using Diligent.WebAPI.Business.Helper;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Diligent.WebAPI.Tests.Helpers
+{
+    public class StringGeneratorTests
+    {
+        [Fact]
+        public void GeneratePassword_ShouldReturn_8_Characters_IfOptionsAreNull()
+        {
+            Assert.Equal(8, StringGenerator.GenerateRandomPassword().Length);
+        }
+
+        [Fact]
+        public void GeneratePassword_ShouldReturn_4_Characters_IfOptionsDefinedLess()
+        {
+            Assert.Equal(4, StringGenerator.GenerateRandomPassword(new Microsoft.AspNetCore.Identity.PasswordOptions
+            {
+                RequiredLength = 3,
+                RequiredUniqueChars = 3,
+                RequireDigit = true,
+                RequireLowercase = true,
+                RequireNonAlphanumeric = true,
+                RequireUppercase = true
+            }).Length);
+        }
+
+        [Fact]
+        public void GeneratePassword_ShouldReturn_15_Characters_IfOptionsHaveDefinedMinLength()
+        {
+            Assert.Equal(15, StringGenerator.GenerateRandomPassword(new Microsoft.AspNetCore.Identity.PasswordOptions
+            {
+                RequiredLength = 15,
+                RequiredUniqueChars = 4,
+                RequireDigit = true,
+                RequireLowercase = true,
+                RequireNonAlphanumeric = true,
+                RequireUppercase = true
+            }).Length);
+        }
+
+        [Fact]
+        public void GeneratePassword_ShouldContainUppercase_IfOptionsAreNull()
+        {
+            Assert.Contains(StringGenerator.GenerateRandomPassword(), char.IsUpper);
+        }
+
+        [Fact]
+        public void GeneratePassword_ShoulContainNumber_IfOptionsAreNull()
+        {
+            Assert.Contains(StringGenerator.GenerateRandomPassword(), char.IsDigit);
+        }
+
+        [Fact]
+        public void GeneratePassword_ShouldNotContainNumber_AfterAddingRandomChars()
+        {
+            Assert.Contains(StringGenerator.GenerateRandomPassword(new Microsoft.AspNetCore.Identity.PasswordOptions
+            {
+                RequiredLength = 12,
+                RequiredUniqueChars = 4,
+                RequireDigit = false,
+                RequireLowercase = true,
+                RequireNonAlphanumeric = true,
+                RequireUppercase = false
+            }), char.IsDigit);
+        }
+
+        [Fact]
+        public void GeneratePassword_ShoulContainSpecialChar_IfOptionsAreNull()
+        {
+            Assert.False(StringGenerator.GenerateRandomPassword().All(char.IsLetterOrDigit));
+        }
+
+        [Fact]
+        public void GeneratePassword_ShouldContainSpecialChar_IfOptionsAreDefinedToAddRandomChars()
+        {
+            Assert.False(StringGenerator.GenerateRandomPassword(new Microsoft.AspNetCore.Identity.PasswordOptions
+            {
+                RequiredLength = 12,
+                RequiredUniqueChars = 1,
+                RequireDigit = true,
+                RequireLowercase = true,
+                RequireNonAlphanumeric = false,
+                RequireUppercase = true
+            }).All(char.IsLetterOrDigit));
+        }
+    }
+}

Diligent.WebAPI.Tests/Services/UserServiceTests.cs

 using Diligent.WebAPI.Business.Settings;
 using Diligent.WebAPI.Contracts.DTOs;
 using Diligent.WebAPI.Contracts.DTOs.User;
+using Diligent.WebAPI.Contracts.Exceptions;
 using Diligent.WebAPI.Data;
 using Diligent.WebAPI.Data.Entities;
 using Microsoft.AspNetCore.Identity;
         }
 
         [Fact]
-        public async Task RemoveUser_ShouldDeleteUser()
+        public async Task RemoveUser_ShouldReturnError()
         {
             var databaseContext = await Helpers<User>.GetDatabaseContext(_users);
 
             var service = new UserService(frontSettings, _mockUserManager, _mapper, databaseContext, mailer, _logger);
             await service.RemoveUser(_user);
 
-            var result = await service.GetById(2);
-            result.Should().Be(null);
+            await Assert.ThrowsAsync<EntityNotFoundException>(async () => await service.GetById(2));
         }
 
         [Fact]
 
             Assert.Equal(true, result.IsError);
         }
-
-        //[Fact] To be debuged later
-        //public async Task Invite_ShouldPassIfUserDoesNotExist()
-        //{
-        //    _mockUserManager.FindByEmailAsync(Arg.Any<string>()).Returns<User>(x => null);
-        //    var databaseContext = await Helpers<User>.GetDatabaseContext(_users);
-        //    var frontSettings = Substitute.For<IOptions<FrontEndSettings>>();
-
-        //    var mailer = Substitute.For<IEmailer>();
-        //    mailer.When(x => x.SendEmailAndWriteToDbAsync(Arg.Any<string>(), Arg.Any<string>(), Arg.Any<string>(), Arg.Any<bool>())).Do(x => { });
-
-        //    var service = new UserService(frontSettings, _mockUserManager, _mapper, databaseContext, mailer);
-
-        //    var result = await service.SendRegistrationLink(new InviteDTO
-        //    {
-        //        Email = "string@dilig.net",
-        //        FirstName = "string",
-        //        LastName = "string",
-        //    });
-
-        //    result.Data.Should().BeEquivalentTo(new
-        //    {
-        //        Message = "Link has been sent!"
-        //    });
-        //}
     }
 }