feat: improve tampering test on exercise "Authentication System" (#2193)

* build(deps): bump actions/checkout from 4.1.0 to 4.1.1 (#2192)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4.1.0 to 4.1.1.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@8ade135...b4ffde6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* feat: improve tampering test on exercise "Authentication System"

* feat: improve test readability

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Salvatore Piccione <Salvatore.Piccione@wolterskluwer.com>

Author: 3 people

exercises/concept/authentication-system/.meta/Exemplar.cs

@@ -40,7 +40,7 @@ public Identity Admin
         get { return new Identity { Email = admin.Email, EyeColor = admin.EyeColor }; }
     }
 
-    public IReadOnlyDictionary<string, Identity> GetDevelopers()
+    public IDictionary<string, Identity> GetDevelopers()
     {
         return new ReadOnlyDictionary<string, Identity>(developers);
     }

exercises/concept/authentication-system/AuthenticationSystemTests.cs

@@ -14,6 +14,18 @@ public void GetAdmin()
         Assert.Equal(admin, authenticator.Admin);
     }
 
+    [Fact]
+    [Task(4)]
+    public void CheckAdminCannotBeTampered()
+    {
+        var adminEmail = "admin@ex.ism";
+        var admin = new Identity { EyeColor = "green", Email = adminEmail };
+        var authenticator = new Authenticator(admin);
+        var tamperedAdmin = authenticator.Admin;
+        tamperedAdmin.Email = "admin@hack.ed";
+        Assert.Equal(adminEmail, authenticator.Admin.Email);
+    }
+
     [Fact]
     [Task(5)]
     public void GetDevelopers()
@@ -24,4 +36,15 @@ public void GetDevelopers()
         bool?[] expected = { true, true, true };
         Assert.Equal(expected, actual);
     }
+
+    [Fact]
+    [Task(5)]
+    public void CheckDevelopersCannotBeTampered()
+    {
+        var authenticator = new Authenticator(new Identity { EyeColor = "green", Email = "admin@ex.ism" });
+        IDictionary<string, Identity> devs = authenticator.GetDevelopers();
+
+        Identity tamperedDev = new Identity { EyeColor = "grey", Email = "anders@hack.ed" };
+        Assert.Throws<NotSupportedException>(() => devs["Anders"] = tamperedDev);
+    }
 }