matlab-write-test

name	matlab-write-test
description	Generate and run MATLAB unit tests using matlab.unittest and matlab.uitest. Parameterized tests, fixtures, mocking, coverage analysis, CI/CD with buildtool, app testing with gestures. Use when creating tests, writing test classes, running test suites, checking coverage, testing apps, or validating MATLAB code.
license	https://www.mathworks.com/content/dam/mathworks/license/pmrl/license.md
metadata	{"author":"MathWorks","version":"2.0"}

Testing

Generate, structure, and run MATLAB unit tests using the matlab.unittest framework. Covers class-based tests, parameterized testing, fixtures, mocking, coverage analysis, CI/CD integration, and app testing via MCP.

When to Use

• User asks to write tests for a MATLAB function or class
• User wants to run an existing test suite
• User needs coverage analysis or CI/CD configuration
• Test-driven development — writing tests before implementation
• Testing App Designer apps with programmatic gestures (see reference/app-testing-guidance.md)

When NOT to Use

• Testing Simulink models — use Simulink test skills
• Performance benchmarking — use profiling workflows

Must-Follow Rules

• Present a test plan first — For non-trivial test suites, propose test methods and edge cases for user approval before writing code
• Always use class-based tests — Every test file must inherit from matlab.unittest.TestCase. Never use script-based tests
• No logic in test methods — No if, switch, for, or try/catch. Follow Arrange-Act-Assert. If a test needs conditionals, split into separate methods
• Test public interfaces, not implementation — Never test private methods directly
• Execute via MCP — Use run_matlab_test_file or evaluate_matlab_code to run tests

Workflow

Simple tests (clear behavior, limited scope)

1. Briefly state what you'll test (methods + key edge cases)
2. Write the test file after user confirms

Standard tests (large codebase, multiple files)

1. Gather requirements — Code to test, expected behaviors, error conditions, scope, dependencies
2. Present test plan — List test methods, edge cases, parameterization strategy for approval
3. Implement — Write tests following the patterns below
4. Run — Execute via run_matlab_test_file MCP tool
5. Check coverage — Identify untested paths, add tests

Key Functions

Category	Functions	Purpose
Equality	verifyEqual, verifyNotEqual	Compare values (use AbsTol for floats)
Boolean	verifyTrue, verifyFalse	Check logical conditions
Size/type	verifySize, verifyClass, verifyEmpty	Structural checks
Errors	verifyError	Confirm error is thrown with correct ID
Warnings	verifyWarning, verifyWarningFree	Check warning behavior
Infra	runtests, TestSuite, TestRunner	Run and organize tests
Coverage	CodeCoveragePlugin, CoverageResult	Measure test coverage

Qualification Levels

Level	On failure	When to use
verify	Continues test	Default — most assertions
assert	Stops current test	Setup validation
fatal	Stops entire suite	Environment preconditions
assume	Skips test	Conditional execution (e.g., toolbox check)

Patterns

Basic Test Class

classdef computeAreaTest < matlab.unittest.TestCase
    %computeAreaTest Tests for the computeArea function.

    methods (Test)
        function testSquare(testCase)
            result = computeArea(5, 5);
            testCase.verifyEqual(result, 25);
        end

        function testFloatingPoint(testCase)
            result = computeArea(1/3, 3);
            testCase.verifyEqual(result, 1, AbsTol=1e-12);
        end

        function testNegativeInputErrors(testCase)
            testCase.verifyError( ...
                @() computeArea(-1, 5), 'computeArea:negativeInput');
        end
    end
end

Parameterized Tests

Parameterize only when assertion logic is identical across all cases — only the data varies. Use struct for readable test names:

classdef unitConverterTest < matlab.unittest.TestCase

    properties (TestParameter)
        conversionCase = struct( ...
            'freezing', struct('input', 0, 'expected', 32), ...
            'boiling',  struct('input', 100, 'expected', 212), ...
            'bodyTemp', struct('input', 37, 'expected', 98.6));
    end

    methods (Test)
        function testCelsiusToFahrenheit(testCase, conversionCase)
            result = celsiusToFahrenheit(conversionCase.input);
            testCase.verifyEqual(result, conversionCase.expected, AbsTol=1e-10);
        end
    end
end

For advanced parameterization (combinations, dynamic parameters, ClassSetupParameter), see reference/parameterized-tests-guidance.md.

Setup, Teardown, and Fixtures

Prefer addTeardown over TestMethodTeardown blocks. Use PathFixture to add source folders:

classdef fileProcessorTest < matlab.unittest.TestCase

    methods (TestClassSetup)
        function addSourceToPath(testCase)
            srcFolder = fullfile(fileparts(fileparts(mfilename('fullpath'))), 'src');
            testCase.applyFixture(matlab.unittest.fixtures.PathFixture(srcFolder, ...
                IncludingSubfolders=true));
        end
    end

    methods (Test)
        function testProcessFile(testCase)
            tmpDir = string(tempname);
            mkdir(tmpDir);
            testCase.addTeardown(@() rmdir(tmpDir, 's'));

            testFile = fullfile(tmpDir, "data.csv");
            writematrix(rand(10, 3), testFile);

            result = processFile(testFile);
            testCase.verifySize(result, [10 3]);
        end
    end
end

For built-in fixtures, custom fixtures, and shared fixtures, see reference/fixtures-guidance.md.

Determinism

Seed the RNG and restore it in teardown for reproducible tests:

methods (TestMethodSetup)
    function resetRandomSeed(testCase)
        originalRng = rng;
        testCase.addTeardown(@() rng(originalRng));
        rng(42, "twister");
    end
end

Test Tags

Use TestTags for selective execution:

methods (Test, TestTags = {'Unit'})
    function testFastCalculation(testCase)
        % ...
    end
end

methods (Test, TestTags = {'Integration', 'Slow'})
    function testFullPipeline(testCase)
        % ...
    end
end

Run by tag: runtests('tests', Tag='Unit') or runtests('tests', ExcludeTag='Slow').

Running Tests

Via MCP

Use the run_matlab_test_file MCP tool for test files. For inline runs with filtering:

results = runtests('tests');                            % all tests in folder
results = runtests('tests', Tag='Unit');                % by tag
results = runtests('tests', Name='*Calculator*');       % by name pattern
results = runtests('tests', UseParallel=true);          % parallel execution
results = runtests('tests', Strict=true);               % warnings = failures

Analyzing Results

disp(results);

for r = results([results.Failed])
    fprintf('\nFAILED: %s\n', r.Name);
    disp(r.Details.DiagnosticRecord.Report);
end

Coverage Analysis

import matlab.unittest.TestRunner
import matlab.unittest.plugins.CodeCoveragePlugin
import matlab.unittest.plugins.codecoverage.CoverageResult
import matlab.unittest.plugins.codecoverage.CoverageReport

runner = TestRunner.withTextOutput;
covFormat = CoverageResult;
runner.addPlugin(CodeCoveragePlugin.forFolder('src', ...
    Producing=[covFormat, CoverageReport('coverage-report')]));
results = runner.run(testsuite('tests'));

covResults = covFormat.Result;
disp(covResults);

For coverage gap analysis, use the printCoverageGaps script in reference/test-execution-guidance.md.

CI/CD Integration

Use buildtool with a buildfile.m for CI pipelines. See reference/test-execution-guidance.md for buildfile.m templates and CI configs (GitHub Actions, Azure DevOps, GitLab CI).

App Designer Testing

For testing apps with programmatic UI gestures (press, choose, type, drag), see reference/app-testing-guidance.md.

Key points:

• Inherit from matlab.uitest.TestCase (not matlab.unittest.TestCase)
• Call drawnow after app creation, before first gesture
• Compare uilabel.Text with char ('text'), not string ("text")
• Compare .Enable with matlab.lang.OnOffSwitchState.on/.off

References

Load these on demand — most tests only need what's in this file.

Load when...	Reference
Tests need setup/teardown, temp dirs, path management, shared state	reference/fixtures-guidance.md
Floating-point tolerance selection, constraint objects, custom constraints	reference/constraints-guidance.md
Multiple parameters, dynamic parameters, combination strategies	reference/parameterized-tests-guidance.md
Code depends on external services, needs mock objects or dependency injection	reference/mocking-guidance.md
Running tests in CI, buildtool config, coverage gap analysis	reference/test-execution-guidance.md
Testing App Designer apps with gestures, dialogs, async callbacks	reference/app-testing-guidance.md

Conventions

• Always use class-based tests inheriting from matlab.unittest.TestCase
• Name test files <functionName>Test.m and place in tests/ directory
• Use verify qualifications by default — they let all tests run even if one fails
• Use AbsTol for every floating-point comparison — never rely on exact equality
• No logic in test methods — follow Arrange-Act-Assert
• Use addTeardown for cleanup — it runs even if the test fails
• Use struct-based TestParameter for readable parameterized test names
• Keep test methods focused — test one behavior per method
• Tests must be independent and compatible with parallel execution
• Run tests via the run_matlab_test_file MCP tool for automatic result capture

---

Copyright 2026 The MathWorks, Inc.

---