Updated all unit tests to consistently use the expected value as the first argument in Assert.AreEqual calls. This improves readability and aligns with best practices for test assertions.

Replaces usages of Assert.AreEqual, Assert.IsTrue, and similar assertions with new helper methods such as Assert.HasCount, Assert.IsEmpty, Assert.IsNull, and Assert.IsGreaterThanOrEqualTo across multiple test files. This improves test readability and consistency with updated assertion APIs.

Updated all usages of Assert.HasCount to explicitly cast stream.Position to int. This ensures type consistency and prevents potential issues when stream.Position is a long.

Updated unit tests in Test_ObservableValidator.cs to use Assert.HasCount instead of Assert.AreEqual for collection count assertions. This improves clarity and consistency in test assertions.

Updated assertions in Test_RelayCommandAttribute_WithPartialCommandMethodDefinitions to assign results to the discard variable, improving code clarity and suppressing possible warnings about unused return values.

Replaces Assert.IsTrue(!...) with Assert.IsFalse(...) for clarity in the Test_ObservableValidator_ValidateReturn test.

Added the Microsoft.VisualStudio.TestTools.UnitTesting.ParallelizeAttribute to all MSTest-based unit test project files to enable parallel test execution. This change should improve test run performance by allowing tests to run concurrently.

Moved the ParallelizeAttribute configuration from individual test project files to the shared Community.Toolkit.Common.targets file. This centralizes the configuration and ensures all test projects run tests in parallel by default.