How to test my C++ function

Question

How to test my C++ function

Jiaxin Zhang 60

How to test a C++ function?

My function returns wrong results. I’m debugging.

The only way I can think of is creating a new console application, then copy the function into it and input test data one by one using keyboard.

Do you have better methods?

Thanks!

RLWA32 50,826 Reputation points

2025-10-09T05:11:18.46+00:00

Have you stepped through the function line by line in the debugger?

Doing this allows you to examine variables, intermediate results and flow of control while the function is executing to determine that processing is correct or identify the specific location(s) in the code that contribute to or produce incorrect results.
Castorix31 91,191 Reputation points

2025-10-09T07:24:37.0466667+00:00

As @RLWA32 said, the usual way is to use BP with the Debugger, as explained in MSDN, for example at : https://free.blessedness.top/en-us/visualstudio/debugger/get-started-with-breakpoints?view=vs-2022

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RLWA32 50,826 Reputation points

2025-10-09T05:11:18.46+00:00

Have you stepped through the function line by line in the debugger?

Doing this allows you to examine variables, intermediate results and flow of control while the function is executing to determine that processing is correct or identify the specific location(s) in the code that contribute to or produce incorrect results.
Castorix31 91,191 Reputation points

2025-10-09T07:24:37.0466667+00:00

As @RLWA32 said, the usual way is to use BP with the Debugger, as explained in MSDN, for example at : https://free.blessedness.top/en-us/visualstudio/debugger/get-started-with-breakpoints?view=vs-2022

Answer 1

Thank you reaching out.

Recommended Microsoft Tools & Methods to Test C++ Functions

1. Microsoft Native Unit Test Framework (Visual Studio)

This is the built-in unit testing framework for C++ in Visual Studio.

Steps:

Open your C++ project in Visual Studio.
Add a new Native Unit Test Project via File > Add > New Project.
Write test cases using TEST_CLASS and TEST_METHOD.
Use Assert::AreEqual() or other assertions to validate your function.
Run tests using Test Explorer (Test > Test Explorer).

Benefits:

Integrated with Visual Studio.
Supports code coverage and test traits.
Works with Live Unit Testing (Enterprise edition).

2. TAEF (Test Authoring and Execution Framework)

Used internally at Microsoft, TAEF supports writing automated tests in C++.

Steps:

Install TAEF via internal Microsoft channels or Visual Studio extensions.
Write test cases using TEST_CLASS and TEST_METHOD.
Use VERIFY_ARE_EQUAL() for assertions.
Run tests using TShell or Visual Studio integration.

Benefits:

Supports logging and diagnostics.
Used across Windows and platform teams.

3. Visual Studio Debugger

Ideal for step-by-step inspection of your function.

Steps:

Set breakpoints in your function.
Use F5 to start debugging.
Inspect variables using Watch, Locals, and Immediate Window.
Step through code with F10 (Step Over) and F11 (Step Into).

Benefits:

No need to copy code into a separate console app.
Helps identify logic errors and incorrect values.

4. Live Unit Testing (Visual Studio Enterprise)

Automatically runs tests as you write code.

Steps:

Enable Live Unit Testing via Test > Live Unit Testing > Start.
Write unit tests using the Native Unit Test Framework.
See inline results and coverage directly in the editor.

Benefits:

Continuous feedback.
Highlights failing tests and uncovered code.

5. Microsoft Test Manager (MTM)

For managing manual and automated test cases.

Steps:

Use MTM to create test plans and test suites.
Link test cases to your C++ functions.
Run tests and log results.
Integrate with Azure DevOps for traceability.

Benefits:

Ideal for larger projects and team collaboration.
Supports manual testing workflows.

References for Future Use

Please let us know if you require any further assistance, we’re happy to help.

If you found this information useful, kindly mark this as "Accepted Answer".

Jiaxin Zhang 60 Reputation points

2025-10-09T08:52:41.8966667+00:00

That’s what I want. But,

How to write test cases using TEST_CLASS and TEST_METHOD?

How to use Assert::AreEqual() or other assertions to validate my function?

Thanks!
Varsha Dundigalla(INFOSYS LIMITED) 2,700 Reputation points Microsoft External Staff

2025-10-09T11:18:36.75+00:00

Thank you for reaching out.

If your C++ function gives wrong results, you can easily test it using Visual Studio’s built-in Native Unit Test Framework no extra tools needed.

Basic Idea

TEST_CLASS – groups related test cases (like a test suite).

TEST_METHOD – defines one specific test scenario.

Each test is automatically detected and run in Test Explorer.

Steps to Create and Run Tests

In Visual Studio, go to\ File → New → Project → Visual C++ → Test → Native Unit Test Project

Add your function or include its header file.

Write test methods following the Arrange → Act → Assert pattern.

Example:

TEST_CLASS(AdditionTests) { TEST_METHOD(Add_PositiveNumbers) { int result = Add(2, 3); Assert::AreEqual(5, result); } };

4.Build the project, open Test Explorer, and click Run All to see results.

Useful Assertions

Assert::AreEqual(expected, actual) – checks equality

Assert::IsTrue(condition) / Assert::IsFalse(condition) – checks logic

Assert::IsNull(ptr) / Assert::IsNotNull(ptr) – checks pointers

You can also add a message, for example:\ Assert::AreEqual(5, result, L"Addition failed");

Tip

Name your tests clearly, like:

Add_TwoPositiveNumbers_ReturnsSum

Divide_ByZero_ThrowsException

Summary

Use TEST_CLASS and TEST_METHOD to structure your tests and validate results with assertions.\ Run them through Test Explorer for quick, repeatable verification — all directly within Visual Studio.**
References**

[1] free.blessedness.top

[2] Use the Microsoft Unit Testing Framework for C++ - Visual Studio (Windows) | Microsoft Learn

[3] Assert.AreEqual Method (Microsoft.VisualStudio.TestTools.UnitTesting) | Microsoft Learn

[4] Unit test basics with Test Explorer - Visual Studio (Windows) | Microsoft Learn

Please let us know if you require any further assistance, we’re happy to help.
Jiaxin Zhang 60 Reputation points

2025-10-10T02:20:51.6933333+00:00

Thanks!
Varsha Dundigalla(INFOSYS LIMITED) 2,700 Reputation points Microsoft External Staff

2025-10-10T11:27:22.6033333+00:00

Thank you for your response. We will now proceed with closing the thread as per your confirmation. If you encounter any further issues, please feel free to raise a new thread.

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