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isCompatible

Class: matlab.unittest.fixtures.Fixture
Namespace: matlab.unittest.fixtures

Determine if two fixtures are compatible

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Syntax

tf = isCompatible(fixture1,fixture2)

Description

tf = isCompatible(fixture1,fixture2) reports the compatibility of two fixtures to the testing framework. If the fixtures are compatible, the method returns logical 1 (true). Otherwise, it returns logical 0 (false). Two fixtures are compatible if they are of the same class and if they make the same changes to the environment.

Implement the isCompatible method in your Fixture subclass if the fixture is configurable (for example, if its class constructor accepts input arguments). The framework calls isCompatible to determine whether instances of the same Fixture subclass correspond to the same shared test fixture state. The information about fixture compatibility helps the framework decide when to perform teardown and setup actions. The framework calls the isCompatible method only with two instances of the same class, so you are not required to implement code to handle the case where the fixtures are of different classes.

example

Input Arguments

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Fixture, specified as a matlab.unittest.fixtures.Fixture object.

Attributes

Accessprotected

To learn about attributes of methods, see Method Attributes.

Examples

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Create a configurable fixture that changes the output display format for numeric values. Classes that define configurable fixtures must implement the isCompatible method in addition to the setup method.

In a file named NumericFormatFixture.m in your current folder, create the NumericFormatFixture class by subclassing the matlab.unittest.fixtures.Fixture interface. Add these elements to the class:

  • Format property — Add this property to store the numeric format specified during fixture construction.

  • NumericFormatFixture method — Add this constructor method to set the Format property.

  • setup method — Implement this method so that the fixture changes the output display format to the specified numeric format. To restore the environment when the testing framework tears down the fixture, call the addTeardown method within the setup method.

  • isCompatible method — Implement this method so that the testing framework can test the compatibility of NumericFormatFixture instances when they are used as shared test fixtures.

classdef NumericFormatFixture < matlab.unittest.fixtures.Fixture
    properties (SetAccess=immutable)
        Format (1,1) string
    end

    methods
        function fixture = NumericFormatFixture(fmt)
            fixture.Format = fmt;
        end

        function setup(fixture)
            originalFormat = format;
            fixture.addTeardown(@format,originalFormat)
            format(fixture.Format)
            fixture.SetupDescription = "Set the numeric format to " + ...
                fixture.Format + ".";
            fixture.TeardownDescription =  ...
                "Restored the numeric format to " + ...
                originalFormat.NumericFormat + ".";
        end
    end

    methods (Access=protected)
        function tf = isCompatible(fixture1,fixture2)
            tf = fixture1.Format == fixture2.Format;
        end
    end
end

In your current folder, create three test classes that each use an instance of NumericFormatFixture as a shared test fixture. Each class tests if a numeric value is displayed in the format enforced by the shared test fixture. To simplify this example, the actual value is produced by a call to the formattedDisplayText function. In practice, you test user-defined code.

In a file named TestA.m, create the TestA class.

classdef (SharedTestFixtures={NumericFormatFixture("bank")}) ...
        TestA < matlab.unittest.TestCase
    methods (Test)
        function formatTest(testCase)
            actual = strtrim(formattedDisplayText(pi));
            expected = "3.14";
            testCase.verifyEqual(actual,expected)
        end
    end
end

In a file named TestB.m, create the TestB class.

classdef (SharedTestFixtures={NumericFormatFixture("bank")}) ...
        TestB < matlab.unittest.TestCase
    methods (Test)
        function formatTest(testCase)
            actual = strtrim(formattedDisplayText(100/3));
            expected = "33.33";
            testCase.verifyEqual(actual,expected)
        end
    end
end

In a file named TestC.m, create the TestC class.

classdef (SharedTestFixtures={NumericFormatFixture("hex")}) ...
        TestC < matlab.unittest.TestCase
    methods (Test)
        function formatTest(testCase)
            actual = strtrim(formattedDisplayText(1));
            expected = "3ff0000000000000";
            testCase.verifyEqual(actual,expected)
        end
    end
end

The TestA and TestB classes are assigned shared fixtures that make the same change to the environment. On the other hand, the TestC class is assigned a fixture that enforces a different numeric format. According to the implementation of the isCompatible method in this example, the testing framework finds the fixtures on TestA and TestB compatible. However, it finds the fixture on TestC incompatible with the other fixtures.

The information about fixture compatibility helps the framework decide when to perform teardown and setup actions. If you run TestA, TestB, and TestC as part of the same test suite, the framework does not tear down the fixture when switching from TestA to TestB because both classes require the same environment. However, when switching from TestB to TestC, the framework tears down the existing fixture and sets up a fresh fixture required by TestC. In this example, all the tests pass.

runtests(["TestA" "TestB" "TestC"]);
Setting up NumericFormatFixture
Done setting up NumericFormatFixture: Set the numeric format to bank.
__________

Running TestA
.
Done TestA
__________

Running TestB
.
Done TestB
__________

Tearing down NumericFormatFixture
Done tearing down NumericFormatFixture: Restored the numeric format to short.
__________

Setting up NumericFormatFixture
Done setting up NumericFormatFixture: Set the numeric format to hex.
__________

Running TestC
.
Done TestC
__________

Tearing down NumericFormatFixture
Done tearing down NumericFormatFixture: Restored the numeric format to short.
__________

Version History

Introduced in R2014a

See Also

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