C Code Verification with Simulink Test

Perform verification and coverage analysis for C Code used in a model.

This example shows how to verify C code with two tests: An interactive test using HMI controls, and a logical test of the code output during simulation.

The C Code is integrated into a model with a C Caller block. The tests use the Test Manager, test harnesses, Test Sequence block, Test Assessment block, and Simulink® Dashboard blocks. Test results include signal outputs and model coverage. verify statements assess the C code during simulation.

Open the Example Project

1. Create and open a working copy of the Simulink Project files. The models and test harness files are in the Models folder. The source and header files for the custom C code are in the CCode folder. The test file is in the Tests folder.

proj = simulinkproject(projectFolder);

2. Open the sltestCruiseControlExample model.

mdl = 'sltestCruiseControlExample';

The block C Function Caller integrates C code defined in RejectDoublePress.c. The C code is a utility function that detects when the Coast/Set and Accelerate/Resume inputs are simultaneously set to true by the user, and outputs false for both signals. Otherwise, the input values are transferred to the outputs:

void RejectDoublePress(unsigned char CoastSetSwIN, unsigned char AccelResSwIN,
unsigned char *CoastSetSwOUT, unsigned char *AccelResSwOUT)
  unsigned char LogicalOperator;
  LogicalOperator = !(CoastSetSwIN && AccelResSwIN);
  *CoastSetSwOUT = (LogicalOperator && CoastSetSwIN);
  *AccelResSwOUT = (LogicalOperator && AccelResSwIN);

Interactive Testing with HMI Controls

The C Caller block has two test harnesses. Open sltestCruiseControlSimpleHarness:

1. Click the harness perspective badge at the bottom right corner of the C Function Caller block.

2. Click the sltestCruiseControlSimpleHarness tile.

sltest.harness.open([mdl, '/C Function Caller'], 'sltestCruiseControlSimpleHarness');

The test harness implements an interactive test of the C algorithm. You can control the Coast/Set and Accelerate/Resume inputs with the slider switches. Lamps display the component output values.

3. Run the test harness simulation by clicking Play in the Simulink toolstrip.

4. Toggle the inputs to try various input combinations. Verify the expected behavior, in particular that the outputs are false when both inputs are true.

5. Click the Stop button to end the simulation.

6. Close the test harness.

close_system('sltestCruiseControlSimpleHarness', 0);

Logical Test with the Test Sequence Block

You can use a Test Sequence block to test combinations of inputs and verify expected behavior. Open the sltestCruiseControlTestSeqHarness harness, the Test Sequence block, and the Test Assessment block.

sltest.harness.open([mdl, '/C Function Caller'], 'sltestCruiseControlTestSeqHarness');
open_system('sltestCruiseControlTestSeqHarness/Test Sequence');
open_system('sltestCruiseControlTestSeqHarness/Test Assessment');

The Test Sequence block steps through the four possible Boolean input combinations. The Test Assessment block uses the active step of the Test Sequence block to activate verifications of the expected outputs for each of the corresponding input conditions. In particular, when both inputs are true, both outputs are verified to be false.

Run the Logical Test

Run the test and view the results of the verify statements:

1. Open the Test Manager.


2. Open the sltestCruiseControlCTests.mldatx test file. The test file has a single test case that runs the sltestCruiseControlTestSeqHarness test harness.


3. Run the test file by clicking Play in the Test Manager toolstrip.


Each verify statement in the Test Assessment block produces a signal trace in the test results. Verify that each statement passes for the time steps that it is active.

The test also returns coverage for the C Code. In the Results and Artifacts pane of the Test Manager, highlight the test case and expand the Aggregated Coverage Results section. The code coverage is 100% for decision, condition, and MCDC metrics. For more information, see Coverage for Custom C/C++ Code in Simulink Models (Simulink Coverage).


Clear results, close open windows, and close models.

close_system(mdl, 0);
clear mdl;