# Write Simple Test Case Using Functions

You can test your MATLAB® program by defining unit tests within a single file that contains a main function and local test functions. In a function-based test, each local function executes a portion of the software and qualifies the correctness of the produced result. For more information about function-based tests, see Write Function-Based Unit Tests.

This example shows how to write a function-based test to qualify the correctness of a function defined in a file in your current folder. The `quadraticSolver` function takes as inputs the coefficients of a quadratic polynomial and returns the roots of that polynomial. If the coefficients are specified as nonnumeric values, the function throws an error.

```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 Tests

To test the `quadraticSolver` function, create the test file `quadraticSolverTest.m` in your current folder. Then, define a main function and two local functions in the file to test `quadraticSolver` against real and imaginary solutions. The name of the main and local functions must start or end with the word "test", which is case-insensitive. Additionally, the name of the main function must correspond to the name of your test file.

#### Define Main Function

To run function-based unit tests, you must define a main function that collects all of the local test functions into a test array. Define the main function `quadraticSolverTest` in your test file. The main function calls `functiontests` to generate the test array `tests`. Pass `localfunctions` to `functiontests` to automatically generate a cell array of function handles to the local functions in your file.

```function tests = quadraticSolverTest tests = functiontests(localfunctions); end ```

#### Define Local Test Functions

Add local functions to the test file to test the `quadraticSolver` function against real and imaginary solutions. The order of the tests within the file does not matter. Each local function must accept a single input `testCase`, which is a `matlab.unittest.FunctionTestCase` object. The testing framework automatically generates this object. The function uses the object to perform qualifications for testing values and responding to failures.

Define a local function `testRealSolution` to verify that `quadraticSolver` returns the correct real solutions for specific coefficients. For example, the equation ${x}^{2}-3x+2=0$ has real solutions $x=1$ and $x=2$. The function calls `quadraticSolver` with the coefficients of this equation. Then, it uses the `verifyEqual` qualification function to compare the actual output `actSolution` to the expected output `expSolution`.

```function tests = solverTest tests = functiontests(localfunctions); end function testRealSolution(testCase) actSolution = quadraticSolver(1,-3,2); expSolution = [2 1]; verifyEqual(testCase,actSolution,expSolution) end ```

Define a second local function `testImaginarySolution` to verify that `quadraticSolver` returns the correct imaginary solutions for specific coefficients. For example, the equation ${x}^{2}+2x+10=0$ has imaginary solutions $x=-1+3i$ and $x=-1-3i$. Just like the previous function, this function calls `quadraticSolver` with the coefficients of this equation, and then uses the `verifyEqual` qualification function to compare the actual output `actSolution` to the expected output `expSolution`.

```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 Test File

Use the `runtests` function to run the tests defined in the `quadraticSolverTest.m` file. In this example, both of the tests pass.

`results = runtests('quadraticSolverTest.m')`
```Running quadraticSolverTest .. Done quadraticSolverTest __________ ```
```results = 1×2 TestResult array with properties: Name Passed Failed Incomplete Duration Details Totals: 2 Passed, 0 Failed, 0 Incomplete. 0.89529 seconds testing time. ```

You also can run tests using the `run` function.

`results = run(quadraticSolverTest)`
```Running quadraticSolverTest .. Done quadraticSolverTest __________ ```
```results = 1×2 TestResult array with properties: Name Passed Failed Incomplete Duration Details Totals: 2 Passed, 0 Failed, 0 Incomplete. 0.017825 seconds testing time. ```