## Write Simple Test Case Using Functions

This example shows how to write a unit test for a MATLAB® function, `quadraticSolver.m`.

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 testing 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.