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Analyze Model Coverage by Using the Simulink Test Manager

If you have a Simulink® Test™ license, you can collect coverage directly from the Test Manager. For more information about Simulink Test, see Get Started with Simulink Test (Simulink Test).

When you analyze coverage for a model, Simulink Coverage™ reports on and highlights the model objects in your design that were exercised during simulation. Use the Test Manager to explore tests and aggregated coverage to see which tests exercise certain model objects. You can run multiple tests in a test suite, analyze coverage for each test, then view the aggregated results for the result set in the Test Manager. Use the coverage reports and model highlighting to learn which parts of your model activated during the specified test cases.

Open the Model

Open the slvnvdemo_powerwindow model. The slvnvdemo_powerwindow model contains a power window controller and a low-order plant model. The controller is implemented with a Stateflow® chart.

Choose Your Coverage Metrics

On the Apps tab, click Simulink Test to open the Tests tab. Click Simulink Test Manager.

This example includes a test file. In the Test Manager, click Open. In the Open File window, select powerwindow_tests.mldatx.

In the Test Browser pane, click powerwindow_tests. Then expand the coverage options by clicking Coverage Settings.

Simulink Test Manager showing an open test file, which contains one test suite titled Powerwindow Test Suite. The test suite contains two test cases.

To enable coverage for the model, under Coverage to Collect, select Record coverage for system under test. Under Coverage Metrics, you can select the metrics you want to report. For information about the coverage metrics, see Structural Coverage Metrics.

For this example, select Decision, Condition, and MCDC.

Run A Test and Collect Coverage

There are two tests in the powerwindow_tests test file. Test Case 1 has the Signal Editor scenario set to Driver, and is the default setting in the model. Test Case 2 has the Signal Editor scenario set to Passenger.

In the Test Manager, you can run individual tests or entire test suites by selecting them in the Test Browser and clicking Run. Select Test Case 1 and click Run.

When the test finishes, the Results and Artifacts tab opens. Click the results for the test to see a summary of the coverage results.

Simulink Test Manager showing results for test case 1. Coverage reported is: 71% decision, 79% condition, 32% MCDC, and 100% execution.

Test Case 1 is the case where the Signal Editor scenario is set to Driver. You can click the name of the model in the Analyzed Model column of the Coverage Results table to display the coverage results in the model with model highlighting enabled. The Coverage Details pane also opens in the Simulink window.

Simulink window after simulation with coverage enabled. The model is highlighted, some blocks are green, red, and grey. On the right side of the model, a coverage report is open, docked in the Simulink window.

The window_system subsystem is green because every block inside the subsystem received 100% coverage. The other subsystems are red because one or more blocks inside did not receive full coverage.

You can point to a subsystem to see a short summary of coverage for each relevant metric. For example, point to the power_window_control_system subsystem block.

Coverage results popup. Decision 100% (2/2), Condition 79% (62/78), MCDC 32% (7/22), Execution 100% (39/39).

If you left click on a block, the Coverage Details pane displays the section of the report for that block. For example, click on the power_window_control_system subsystem.

Simulink window after clicking on a subsystem. The docked coverage report shows the section of the report that details coverage results for the subsystem.

You can enter a subsystem to view the granular coverage results for the contents of that subsystem. Double-click the power_window_control_system subsystem and view the coverage results for the blocks it contains. Double-click on validate_passenger, then check_up.

Click the And block allow_action to display the relevant section of the report.

Simulink window after clicking on the And block. The And block is red and the coverage report is displayed on the right.

Click the And block to see the condition and MCDC results. Because the And block outputs the logical combination of the two input signals, if both input signals are true, the output signal is true. You can see from the condition table that input signal 1 was false at every time step, while input signal 2 was true for 878 time steps and false for 884 time steps. Because there are four condition outcomes and one of them did not occur, the allow_action block received 75% condition coverage.

The MCDC analysis table lists decision reversals that occur because one condition outcome changes from true to false or from false to true. This table reports that only the FF case occurred for the first condition, and neither MCDC objective occurred for the second condition, which results in 0% MCDC reported.

Run Multiple Tests and View Aggregated Coverage

In the slvnvdemo_powerwindow model, the And block power_window_control_system/validate_passenger/check_up/allow_action has 75% condition coverage because the Signal Editor block Input at the model root level has the Active scenario set to Driver. This missing coverage can be resolved by including Test Case 2 in the coverage analysis.

In the Test Manager, open the Test Browser tab. Click Powerwindow Test Suite, then click Run to run all the tests in the test suite. When the tests finish, the Test Manager opens the Results and Artifacts pane. Expand results for the new test. You can view the coverage results for each individual test by expanding each test case.

Select Powerwindow Test Suite, then click the model name, slvnvdemo_powerwindow, to open the model with coverage highlighting. Navigate to power_window_control_system/validate_passenger/check_up and click the And block. In the coverage report, the condition coverage is now 100%. Additionally, the T1 and T2 link in the condition and MCDC tables link to the test that satisfies each objective. For example, the true case of the first condition was satisfied by test case 2, T2. Click the link to scroll to the Aggregated Tests section of the report.

In the Test Manager, in the Aggregated Coverage Results table, the overall coverage results improved. When you click on the test suite or the test file name, you see the aggregated coverage results for all tests inside.

Simulink Test Manager on the Results and Artifacts tab with Powerwindow Test Suite selected. Coverage results are: 86% decision, 92% condition, 45% MCDC, and 100% execution.

The aggregated results show higher coverage percentages than either of the two individual test cases because the test cases satisfy different objectives in some blocks.

Filter Coverage Outcomes

If you analyze the coverage report and find that you are missing coverage that is not possible to fix by changing the model or a test case, you can filter the missing outcomes so that they are not reported as missing coverage. Although you cannot filter coverage directly from the Test Manager, you can measure the effect that the coverage filters have on the model. Some possible reasons you might want to filter coverage outcomes include:

  • A block is tested by a different test suite, and is not applicable to the current coverage analysis.

  • A block is intended to catch edge cases that you think should never occur anyway. This type of model design is sometimes called defensive coding.

There are two types of coverage filters:

  • An exclusion filter rule can be applied to a model element, and causes that element to be ignored by coverage analysis. The excluded model elements appear dimmed in the highlighted model, like other elements that are not applicable to the metrics you selected.

  • A justification filter rule can be applied to a coverage outcome that is not satisfied. This filter rule allows Simulink Coverage to analyze the rest of the model element but does not report the justified outcome as missing coverage. This filter rule allows you to improve your coverage for a model object without excluding it entirely.

Suppose that the And block condition 1 MCDC outcome has been tested by a different test suite and is not applicable for this case. You can justify the outcome so that it is not reported as missing coverage.

In the model, navigate to the subsystem power_window_control_system/validate_passenger/check_up and click the And block allow_action to scroll to the relevant section in the coverage report. The MCDC condition C1 (allow_action In1) is incomplete because the TF case did not occur. To justify the C1 (allow_action In1) MCDC outcome, click the Add justification rule icon .

The Coverage Results Explorer opens the Filter Editor pane with a new untitled filter file. The filter file contains a justification rule for the specified outcome. You can add multiple filter rules to the same filter file.

The Filter Editor showing the new Untitled filter.

In the Name field, enter slvnvdemo_powerwindow_filter. Under Filter Rules, double-click the Rationale field and enter Tested in a different test suite. Click Apply, then save the file. The model and coverage report automatically update to indicate that the outcome is justified.

Simulink window after clicking on the And block. The docked coverage report shows the section of the report that details coverage results for the And block, and the C1 MCDC outcome is highlighted cyan to indicate that it is justified.

In the Coverage Details pane, the justified outcome is highlighted in cyan and links to the justification rationale. Clicking J1 brings you to the section of the report titled Objects Filtered from Coverage Analysis. This section of the report only appears if there are filters applied to the coverage data.

Go back to the Test Manager. Click the result set. In the Aggregated Coverage Results section, the coverage filter has been applied automatically, and the MCDC coverage result is now 50%.

Note

You must click on a the top-level results to see the applied coverage filters. The filter is not included in test suite or test case results.

To apply another coverage filter file, click the results set, expand the Coverage Filters section, and then click Add.

Create and Archive Reports

To create a coverage report, click the arrow in the Report column. Alternatively, you can click Export under the Aggregated Coverage Results table. Then use cvhtml to create a coverage report. For example, export the results with the variable name coverageData and then enter:

cvhtml('testManager_covData',coverageData)

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