Collect Code Coverage Metrics for MATLAB Source Code

Collect and Analyze Code Coverage Information

In your current folder, save the QuadraticPolynomial class definition in a file named QuadraticPolynomial.m. Then, create the QuadraticPolynomialTest test class in your current folder. The test class has four Test methods:

classdef QuadraticPolynomialTest < matlab.unittest.TestCase
    methods (Test)
        function realSolution(testCase)
            p = QuadraticPolynomial(1,-3,2);
            actSolution = p.solve();
            expSolution = [1 2];
            testCase.verifyEqual(actSolution,expSolution)
        end
        function imaginarySolution(testCase)
            p = QuadraticPolynomial(1,2,10);
            actSolution = p.solve();
            expSolution = [-1-3i -1+3i];
            testCase.verifyEqual(actSolution,expSolution)
        end
        function nonnumericInput(testCase)
            testCase.verifyError(@()QuadraticPolynomial(1,"-3",2), ...
                "QuadraticPolynomial:InputMustBeNumeric")
        end
        function plotPolynomial(testCase)
            p = QuadraticPolynomial(1,-3,2);
            fig = figure;
            testCase.addTeardown(@close,fig)
            ax = axes(fig);
            p.plot(ax)
            actYLabelText = ax.YLabel.String;
            expYLabelText = '1.00x^2-3.00x+2.00';
            testCase.verifyEqual(actYLabelText,expYLabelText)
        end
    end
end

To run tests and perform a code coverage analysis, first create a test runner with a plugin that provides programmatic access to information on all possible coverage types for the source code in the file QuadraticPolynomial.m.

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

runner = testrunner("textoutput");
format = CoverageResult;
plugin = CodeCoveragePlugin.forFile("QuadraticPolynomial.m", ...
    Producing=format,MetricLevel="mcdc");
addPlugin(runner,plugin)

Create a test suite from the QuadraticPolynomialTest class and run the tests. All the tests pass.

suite = testsuite("QuadraticPolynomialTest");
run(runner,suite);

Running QuadraticPolynomialTest
...

.
Done QuadraticPolynomialTest
__________

After the test run, the Result property of the CoverageResult object holds the coverage result. You can use this result to programmatically access information about different coverage types. Additionally, you can generate a code coverage report from the result.

result = format.Result;

The QuadraticPolynomial class definition file has a single decision composed of three conditions. Access the decision coverage summary from the coverage result. The returned vector indicates that both the decision outcomes in the source code were achieved by the tests.

decisionSummary = coverageSummary(result,"decision")

decisionSummary = 1×2

     2     2

Access the condition coverage summary. The summary indicates that the condition coverage is 66.7% because the tests missed two of the six possible condition outcomes in the QuadraticPolynomial class definition file.

conditionSummary = coverageSummary(result,"condition")

conditionSummary = 1×2

     4     6

Generate Code Coverage Report

Generate an HTML code coverage report from the coverage result. The report displays information about the collected code coverage information and uses different colors to highlight the executed or missed outcomes.

generateHTMLReport(result)

You can interact with the code coverage report. For example, in the Overall Coverage Summary section, you can select a coverage type from the Currently viewing list to view detailed information about that coverage type. The report has three sections:

For example, this figure shows the condition coverage view of the report. The Source Details section indicates that only the second condition in the source file was evaluated to both true and false. You can refer to the Condition column to learn how the tests evaluated each condition. For instance, T: 4, 3, 3 shows that the tests evaluated the conditions to true for the specified number of times. On the other hand, F: 0, 1, 0 shows that the second condition was evaluated to false a single time whereas the other two conditions were not evaluated to false. Out of six possible condition outcomes (that is, true and false for each of the three conditions), the tests achieved only four outcomes.

Now, access the MC/DC view of the report by selecting MC/DC from the Currently viewing list. MC/DC identifies how tests independently exercise conditions within decisions. A condition receives MC/DC if tests can:

To examine these requirements, the testing framework finds the combinations of condition outcomes that tests must achieve for each condition. For example, this figure shows the Source Details section for the MC/DC type. The MC/DC column provides a pair of combinations for each condition, where T, F, and x denote true, false, and don't-care values, respectively. Achieving both combinations for a condition ensures that the condition evaluates to both true and false and that it independently affects the outcome of the decision:

Out of the Txx, FFF, FTx, and FFT combinations, the tests achieved only the FFF and FTx combinations. Therefore, only the second condition satisfied the MC/DC requirements.

QuadraticPolynomial Class Definition

This code provides the complete contents of the QuadraticPolynomial class.

classdef QuadraticPolynomial
    properties
        A,B,C   % Coefficients of a*x^2 + b*x + c
    end

    methods
        function obj = QuadraticPolynomial(a,b,c)
            if ~isa(a,"numeric") || ~isa(b,"numeric") || ~isa(c,"numeric")
                error("QuadraticPolynomial:InputMustBeNumeric", ...
                    "Coefficients must be numeric.")
            else
                obj.A = a; obj.B = b; obj.C = c;
            end
        end

        function roots = solve(obj)
            % Return solutions to a*x^2 + b*x + c = 0
            delta = calculateDelta(obj);
            roots(1) = (-obj.B - sqrt(delta)) / (2*obj.A);
            roots(2) = (-obj.B + sqrt(delta)) / (2*obj.A);
        end

        function plot(obj,ax)
            % Plot a*x^2 + b*x + c around its axis of symmetry
            delta = calculateDelta(obj);
            x0 = -obj.B/(2*obj.A);
            x1 = abs(sqrt(delta))/obj.A;
            x = x0 + linspace(-x1,x1);
            y = obj.A*x.^2 + obj.B*x + obj.C;
            plot(ax,x,y)
            xlabel("x")
            ylabel(sprintf("%.2fx^2%+.2fx%+.2f",obj.A,obj.B,obj.C))
        end
    end

    methods (Access=private)
        function delta = calculateDelta(obj)
            delta = obj.B^2 - 4*obj.A*obj.C;
        end
    end
end