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matlab.unittest.plugins.FailOnWarningsPlugin class

Package: matlab.unittest.plugins

Plugin to fail tests that issue warnings


The FailOnWarningsPlugin creates a plugin that, when added to the TestRunner, fails any test that issues a warning. The plugin produces a qualification failure in the test scope that issues the warning. For example, if a shared test fixture issues a warning, the plugin produces a qualification failure on the fixture and fails all tests that share the fixture.

The FailOnWarningsPlugin plugin does not produce a failure if:

  • A test accounts for the warning through a constraint such as IssuesWarnings or IssuesNoWarnings, regardless of whether the constraint is satisfied or not.

  • A warning is disabled. For example, if you disable a warning using the SupressedWarningsFixture.


matlab.unittest.plugins.FailOnWarningsPlugin creates a plugin that fails any test that issues a warning.

matlab.unittest.plugins.FailOnWarningsPlugin('Ignoring',warnIDs) creates a plugin that does not fail for the specified warning identifiers, warnIDs.

Input Arguments

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Identifiers for warnings to ignore, specified as a cell array of character vectors. The plugin does not fail a test for the warnings with identifiers included in warnIDs.

Example: FailOnWarningsPlugin('Ignoring',{'MATLAB:singularMatrix'})


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The Ignore property is empty by default. To specify the property as a cell array of character vectors, use the 'Ignoring' syntax when you construct the plugin instance.

Copy Semantics

Handle. To learn how handle classes affect copy operations, see Copying Objects.


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Create the solve function to solve a set of linear equations. There is an intentional error in the solve function — the assert call that checks whether the matrix is singular should use rcond instead of det.

function x = solve(A,b)

assert(abs(det(A)) > 1e-12,... % intentional bug for illustrative purposes
    'The matrix is singular or nearly singular'); 

x = A\b;

Create the following test class. In testTwo, the A matrix is singular, but since there is a bug in the solve function, the assert call does not catch it.

classdef TestSolve < matlab.unittest.TestCase
        function testOne(testCase)
            A = eye(3);
            b = [3; 4; 1];

        function testTwo(testCase)
            A = [1e-100 0; 0 1e100];
            b = [5; 5];
            expX = [5e100 5e-100];

At the command prompt, create a test suite, and test runner.

import matlab.unittest.TestRunner;
import matlab.unittest.TestSuite;
import matlab.unittest.plugins.FailOnWarningsPlugin;

suite = TestSuite.fromClass(?TestSolve);
runner = TestRunner.withTextOutput;

Add the FailOnWarningsPlugin plugin, and run the tests. testTwo fails because the solve function issues a warning. Without FailOnWarningsPlugin, the solve function issues the warning, but both tests pass.

result =;
Running TestSolve
.Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 1.000000e-200.
Verification failed in TestSolve/testTwo.

    Framework Diagnostic:
    TestSolve/testTwo issued warnings:    
        Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 1.000000e-200.
            In C:\work\solve.m (solve) at 6
            In C:\work\TestSolve.m (TestSolve.testTwo) at 14

    Stack Information:
    In C:\Program Files\MATLAB\R2015b\toolbox\matlab\testframework\+matlab\+unittest\+plugins\FailOnWarningsPlugin.m (FailOnWarningsPlugin.teardownTestMethod) at 164

Done TestSolve

Failure Summary:

     Name               Failed  Incomplete  Reason(s)
     TestSolve/testTwo    X                 Failed by verification.


  • Set the warning stack trace display using the warning function. For example, warning('off','backtrace').

  • Disable warnings using the SuppressedWarningsFixture class.

Introduced in R2015b