MSTest Testing Skill

Core Patterns

Basic Test

using Microsoft.VisualStudio.TestTools.UnitTesting;

[TestClass]
public class CalculatorTests
{
    private Calculator _calc;

    [TestInitialize]
    public void SetUp() => _calc = new Calculator();

    [TestMethod]
    public void Add_TwoNumbers_ReturnsSum()
    {
        Assert.AreEqual(5, _calc.Add(2, 3));
    }

    [TestMethod]
    [ExpectedException(typeof(DivideByZeroException))]
    public void Divide_ByZero_Throws()
    {
        _calc.Divide(10, 0);
    }
}

Data-Driven Tests

[DataTestMethod]
[DataRow(2, 3, 5)]
[DataRow(-1, 1, 0)]
[DataRow(0, 0, 0)]
public void Add_Parameterized(int a, int b, int expected)
{
    Assert.AreEqual(expected, _calc.Add(a, b));
}

[DataTestMethod]
[DynamicData(nameof(GetTestData), DynamicDataSourceType.Method)]
public void Add_DynamicData(int a, int b, int expected)
{
    Assert.AreEqual(expected, _calc.Add(a, b));
}

private static IEnumerable<object[]> GetTestData()
{
    yield return new object[] { 1, 2, 3 };
    yield return new object[] { 10, -5, 5 };
}

Assertions

Assert.AreEqual(expected, actual);
Assert.AreNotEqual(unexpected, actual);
Assert.IsTrue(condition);
Assert.IsFalse(condition);
Assert.IsNull(obj);
Assert.IsNotNull(obj);
Assert.IsInstanceOfType(obj, typeof(MyClass));
Assert.ThrowsException<ArgumentException>(() => Method());
CollectionAssert.Contains(list, item);
CollectionAssert.AreEquivalent(expected, actual);
StringAssert.Contains(str, "substring");
StringAssert.StartsWith(str, "prefix");
StringAssert.Matches(str, new Regex(@"\d+"));

Lifecycle

[AssemblyInitialize]  → Once per assembly (static)
[ClassInitialize]     → Once per class (static)
[TestInitialize]      → Before each test
[TestMethod]          → Test
[TestCleanup]         → After each test
[ClassCleanup]        → Once after class (static)
[AssemblyCleanup]     → Once after assembly (static)

Categories

[TestMethod, TestCategory("Smoke")]
public void QuickTest() { }

[TestMethod, Ignore("Bug #456")]
public void SkippedTest() { }

[TestMethod, Timeout(5000)]
public void TimedTest() { }

Setup: dotnet add package MSTest.TestFramework MSTest.TestAdapter Microsoft.NET.Test.Sdk

Run: dotnet test or dotnet test --filter "TestCategory=Smoke"

Deep Patterns

See reference/playbook.md for production-grade patterns:

Section	What You Get
§1 Project Setup	.csproj deps, .runsettings with parallel + coverage config
§2 Test Patterns	TestMethod, DataTestMethod, DynamicData, exception testing
§3 FluentAssertions	AssertionScope, async exceptions, collection assertions
§4 Class & Assembly Initialize	Testcontainers, shared expensive setup, global config
§5 WebApplicationFactory	API integration tests with in-memory DB
§6 Bogus Test Data	Faker patterns for realistic data generation
§7 TestContext & Logging	Diagnostic output, categories, timeouts
§8 CI/CD Integration	GitHub Actions with coverage reporting and thresholds
§9 Debugging Table	12 common problems with causes and fixes
§10 Best Practices	14-item production checklist