Visual-studio – How to persist variables between tests in MSTest

mstestunit testingvisual studio

I'm using MSTest (VS2008) and I need to persist a variable between tests. However the variable gets re-initialized between every test.

According to the third point mentioned in this answer,

MSTest always instantiates a new instance of the test class for each test method being executed.

Is there a straightforward way to keep the value of a variable between tests, or somehow suppress this behaviour?

Best Answer

Use a static member variable:

static int _test = 0;

[TestMethod]
public void __Test1()
{
    _test += 1;
    Assert.IsTrue(_test == 1);
}

[TestMethod]
public void __Test2()
{
    _test += 1;
    Assert.IsTrue(_test == 2);
}

Related Solutions

Java – How to test a class that has private methods, fields or inner classes

Update:

Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via @Jailbreak from the Manifold framework.
@Jailbreak Foo foo = new Foo();
// Direct, *type-safe* access to *all* foo's members
foo.privateMethod(x, y, z);
foo.privateField = value;
This way your code remains type-safe and readable. No design compromises, no overexposing methods and fields for the sake of tests.

If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection.

Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. The following patterns will let you do pretty much anything related to the private methods and fields. Of course, you can't change private static final variables through reflection.

Method method = TargetClass.getDeclaredMethod(methodName, argClasses);
method.setAccessible(true);
return method.invoke(targetObject, argObjects);

And for fields:

Field field = TargetClass.getDeclaredField(fieldName);
field.setAccessible(true);
field.set(object, value);

Notes:
1. TargetClass.getDeclaredMethod(methodName, argClasses) lets you look into private methods. The same thing applies for getDeclaredField.
2. The setAccessible(true) is required to play around with privates.

C# – How to use Assert to verify that an exception has been thrown

For "Visual Studio Team Test" it appears you apply the ExpectedException attribute to the test's method.

Sample from the documentation here: A Unit Testing Walkthrough with Visual Studio Team Test

[TestMethod]
[ExpectedException(typeof(ArgumentException),
    "A userId of null was inappropriately allowed.")]
public void NullUserIdInConstructor()
{
   LogonInfo logonInfo = new LogonInfo(null, "P@ss0word");
}

Best Answer

Related Solutions

Java – How to test a class that has private methods, fields or inner classes

C# – How to use Assert to verify that an exception has been thrown

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