Documentation

Create quadraticSolver.m Function

This MATLAB function solves quadratic equations. Create this function in a folder on your MATLAB path.

function roots = quadraticSolver(a, b, c)
% quadraticSolver returns solutions to the 
% quadratic equation a*x^2 + b*x + c = 0.

if ~isa(a,'numeric') || ~isa(b,'numeric') || ~isa(c,'numeric')
    error('quadraticSolver:InputMustBeNumeric', ...
        'Coefficients must be numeric.');
end

roots(1) = (-b + sqrt(b^2 - 4*a*c)) / (2*a);
roots(2) = (-b - sqrt(b^2 - 4*a*c)) / (2*a);

end

Create solverTest Function

Create this function in a folder on your MATLAB path.

function tests = solverTest
tests = functiontests(localfunctions);
end

A call to functiontests using localfunctions as input creates an array of tests from each local function in the solverTest.m file. Each test is a local function that follows the naming convention of having ’test’ at the beginning or end of the function name. Local functions that do not follow this convention are not included in the test array. Test functions must accept a single input argument into which the test framework passes a function test case object. The function uses this object for verifications, assertions, assumptions, and fatal assertions. It contains a TestData structure that allows data to be passed between setup, test, and teardown functions.

Create Test Function for Real Solutions

Create a test function, testRealSolution, to verify that quadraticSolver returns the correct value for real solutions. For example, the equation x2 - 3x + 2 = 0 has real solutions x = 1 and x = 2. This function calls quadraticSolver with the inputs of this equation. The expected solution, expSolution, is [2,1].

Use the qualification function, verifyEqual, to compare the output of the function, actSolution, to the desired output, expSolution. If the qualification fails, the framework continues executing the test. Typically, when using verifyEqual on floating point values, you specify a tolerance for the comparison. For more information, see matlab.unittest.constraints.

Add this function to the solverTest.m file.

function testRealSolution(testCase)
actSolution = quadraticSolver(1,-3,2);
expSolution = [2 1];
verifyEqual(testCase,actSolution,expSolution)
end

Create Test Function for Imaginary Solutions

Create a test to verify that quadraticSolver returns the right value for imaginary solutions. For example, the equation x2 + 2x + 10 = 0 has imaginary solutions x = -1 + 3i and x = -1 - 3i. Typically, when using verifyEqual on floating point values, you specify a tolerance for the comparison. For more information, see matlab.unittest.constraints.

Add this function, testImaginarySolution, to the solverTest.m file.

function testImaginarySolution(testCase)
actSolution = quadraticSolver(1,2,10);
expSolution = [-1+3i -1-3i];
verifyEqual(testCase,actSolution,expSolution)
end

The order of the tests within the solverTest.m file does not matter because they are fully independent test cases.

Save solverTest Function

The following is the complete solverTest.m test file. Save this file in a folder on your MATLAB path.

function tests = solverTest
tests = functiontests(localfunctions);
end

function testRealSolution(testCase)
actSolution = quadraticSolver(1,-3,2);
expSolution = [2 1];
verifyEqual(testCase,actSolution,expSolution)
end

function testImaginarySolution(testCase)
actSolution = quadraticSolver(1,2,10);
expSolution = [-1+3i -1-3i];
verifyEqual(testCase,actSolution,expSolution)
end

Run Tests in solverTest Function

Run the tests.

results = runtests('solverTest.m')

Running solverTest
..
Done solverTest
__________


results = 

  1x2 TestResult array with properties:

    Name
    Passed
    Failed
    Incomplete
    Duration

Totals:
   2 Passed, 0 Failed, 0 Incomplete.
   0.19172 seconds testing time.

Both of the tests passed.

Introduce an Error in quadraticSolver.m and Run Tests

Cause one of the tests to fail by forcing roots in quadraticSolver.m to be real. Before ending the function, add the line: roots = real(roots);. (Do not change solverTest.m.) Save the file and run the tests.

results = runtests('solverTest.m')

Running solverTest
.
================================================================================
Verification failed in solverTest/testImaginarySolution.

    ---------------------
    Framework Diagnostic:
    ---------------------
    verifyEqual failed.
    --> Complexity does not match.
        
        Actual Complexity:
            Real
        Expected Complexity:
            Complex
    
    Actual Value:
            -1    -1
    Expected Value:
         -1.000000000000000 + 3.000000000000000i -1.000000000000000 - 3.000000000000000i

    ------------------
    Stack Information:
    ------------------
    In C:\work\solverTest.m (testImaginarySolution) at 14
================================================================================
.
Done solverTest
__________

Failure Summary:

     Name                              Failed  Incomplete  Reason(s)
    ===============================================================================
     solverTest/testImaginarySolution    X                 Failed by verification.
    

results = 

  1x2 TestResult array with properties:

    Name
    Passed
    Failed
    Incomplete
    Duration

Totals:
   1 Passed, 1 Failed, 0 Incomplete.
   0.043751 seconds testing time.

The imaginary test verification failed.

Restore quadraticSolver.m to its previous, correct version by removing the roots = real(roots); code.