Added some TrySetProperty tests

Author: Sergio0694

UnitTests/UnitTests.Shared/Mvvm/Test_ObservableValidator.cs

@@ -153,6 +153,60 @@ public void Test_ObservableValidator_ValidateReturn(string value, bool isValid)
             }
         }
 
+        [TestCategory("Mvvm")]
+        [TestMethod]
+        public void Test_ObservableValidator_TrySetProperty()
+        {
+            var model = new Person();
+            var events = new List<DataErrorsChangedEventArgs>();
+
+            model.ErrorsChanged += (s, e) => events.Add(e);
+
+            // Set a correct value, this should update the property
+            Assert.IsTrue(model.TrySetName("Hello", out var errors));
+            Assert.IsTrue(errors.Count == 0);
+            Assert.IsTrue(events.Count == 0);
+            Assert.AreEqual(model.Name, "Hello");
+            Assert.IsFalse(model.HasErrors);
+
+            // Invalid value #1, this should be ignored
+            Assert.IsFalse(model.TrySetName(null, out errors));
+            Assert.IsTrue(errors.Count > 0);
+            Assert.IsTrue(events.Count == 0);
+            Assert.AreEqual(model.Name, "Hello");
+            Assert.IsFalse(model.HasErrors);
+
+            // Invalid value #2, same as above
+            Assert.IsFalse(model.TrySetName("This string is too long for the target property in this model and should fail", out errors));
+            Assert.IsTrue(errors.Count > 0);
+            Assert.IsTrue(events.Count == 0);
+            Assert.AreEqual(model.Name, "Hello");
+            Assert.IsFalse(model.HasErrors);
+
+            // Correct value, this should update the property
+            Assert.IsTrue(model.TrySetName("Hello world", out errors));
+            Assert.IsTrue(errors.Count == 0);
+            Assert.IsTrue(events.Count == 0);
+            Assert.AreEqual(model.Name, "Hello world");
+            Assert.IsFalse(model.HasErrors);
+
+            // Actually set an invalid value to show some errors
+            model.Name = "No";
+
+            // Errors should now be present
+            Assert.IsTrue(model.HasErrors);
+            Assert.IsTrue(events.Count == 1);
+            Assert.IsTrue(model.GetErrors(nameof(Person.Name)).Cast<ValidationResult>().Any());
+            Assert.IsTrue(model.HasErrors);
+
+            // Trying to set a correct property should clear the errors
+            Assert.IsTrue(model.TrySetName("This is fine", out errors));
+            Assert.IsTrue(errors.Count == 0);
+            Assert.IsTrue(events.Count == 2);
+            Assert.IsFalse(model.HasErrors);
+            Assert.AreEqual(model.Name, "This is fine");
+        }
+
         public class Person : ObservableValidator
         {
             private string name;
@@ -166,6 +220,11 @@ public string Name
                 set => SetProperty(ref this.name, value, true);
             }
 
+            public bool TrySetName(string value, out IReadOnlyCollection<ValidationResult> errors)
+            {
+                return TrySetProperty(ref name, value, out errors, nameof(Name));
+            }
+
             private int age;
 
             [Range(0, 100)]