Parametrized unit tests in Swift

问题

Is there any way to use parameterized unit tests, similar to what you can achieve in .Net using NUnit framework.

[TestCase(12, 3, 4)]
[TestCase(12, 2, 6)]
[TestCase(12, 4, 3)]
public void DivideTest(int expectedResult, int a, int b)
{
  Assert.AreEqual(expectedResult, a / b);
}

Using this kind of tests (vs non-parameterized ones) can give you bigger back for buck by allowing you to avoid writing series of almost identical unit tests differing only by parameter values.

I am looking for either XCTest-based solution or some other means to achieve it. Optimal solution should report each test case (parameter set) as a separate unit test in Xcode, so is it clear whether all or only some of the tests cases failed.

回答1:

The best way to use parametrized is using the XCTestCase subclass's property defaultTestSuite. A clearly example with devision is the next:

import XCTest

class ParameterizedExampleTests: XCTestCase {

    //properties to save the test cases
    private var array: [Float]? = nil
    private var expectedResult: Float? = nil

    // This makes the magic: defaultTestSuite has the set of all the test methods in the current runtime
    // so here we will create objects of ParameterizedExampleTests to call all the class' tests methodos
    // with differents values to test
    override open class var defaultTestSuite: XCTestSuite {
        let testSuite = XCTestSuite(name: NSStringFromClass(self))
        addTestsWithArray([12, 3], expectedResult: 4, toTestSuite: testSuite)
        addTestsWithArray([12, 2], expectedResult: 6, toTestSuite: testSuite)
        addTestsWithArray([12, 4], expectedResult: 3, toTestSuite: testSuite)
        return testSuite
    }

    // This is just to create the new ParameterizedExampleTests instance to add it into testSuite
    private class func addTestsWithArray(_ array: [Float], expectedResult: Float, toTestSuite testSuite: XCTestSuite) {
        testInvocations.forEach { invocation in
            let testCase = ParameterizedExampleTests(invocation: invocation)
            testCase.array = array
            testCase.expectedResult = expectedResult
            testSuite.addTest(testCase)
        }
    }

    // Normally this function is into production code (e.g. class, struct, etc).
    func division(a: Float, b: Float) -> Float {
        return a/b
    }

    func testDivision() {
        XCTAssertEqual(self.expectedResult, division(a: array?[0] ?? 0, b: array?[1] ?? 0))
    }
}

回答2:

You function parameters are all over the place. I'm not sure if your function is doing multiplication or division. But here's one way you can do multiple test cases in a single test method.

Given this function:

func multiply(_ a: Int, _ b: Int) -> Int {
    return a * b
}

You can have multiple test cases on it:

class MyTest: XCTestCase {
    func testMultiply() {
        let cases = [(4,3,12), (2,4,8), (3,5,10), (4,6,20)]
        cases.forEach {
            XCTAssertEqual(multiply($0, $1), $2)
        }
    }
}

The last two would fail and Xcode will tell you about them.

回答3:

@Code Different's answer is legit. Here's other two options, or rather workarounds:

Property Based Testing

You could use a tool like Fox to perform generative testing, where the test framework will generate many input sets for the behaviour you want to test and run them for you.

BDD Shared Examples

If you like the BDD style and are using a test framework that supports them, you could use shared examples.

Using Quick it would look like:

class MultiplySharedExamplesConfiguration: QuickConfiguration {
  override class func configure(configuration: Configuration) {
    sharedExamples("something edible") { (sharedExampleContext: SharedExampleContext) in
      it("multiplies two numbers") {
        let a = sharedExampleContext()["a"]
        let b = sharedExampleContext()["b"]
        let expectedResult = sharedExampleContext()["b"]

        expect(multiply(a, b)) == expectedResult
      }
    }
  }
}

class MultiplicationSpec: QuickSpec {
  override func spec() {
    itBehavesLike("it multiplies two numbers") { ["a": 2, "b": 3, "result": 6] }
    itBehavesLike("it multiplies two numbers") { ["a": 2, "b": 4, "result": 8] }
    itBehavesLike("it multiplies two numbers") { ["a": 3, "b": 3, "result": 9] }
  }
}

To be honest this option is: 1) a lot of work, 2) a misuse of the shared example technique, as you are not using them to test behaviour shared by multiple classes but rather to parametrise the test. But as I said at the start, this is a more of a workaround.

回答4:

The asserts all seem to throw, so perhaps something like this will work for you:

typealias Division = (dividend: Int, divisor: Int, quotient: Int)

func testDivisions() {
    XCTAssertNoThrow(try divisionTest((12, 3, 4)))
    XCTAssertNoThrow(try divisionTest((12, 2, 6)))
    XCTAssertNoThrow(try divisionTest((12, 4, 3)))
}

private func divisionTest(_ division: Division) throws {
    XCTAssertEqual(division.dividend / division.divisor, division.quotient)
}

If one fails, the entire function will fail. If more granularity is required, every case can be split up into an individual function.

回答5:

We found that this solution How to Dynamically add XCTestCase offers us the flexibility we need. Being able to dynamically add tests, pass arguments to tests, and display the dynamic test names in the test report.

来源：https://stackoverflow.com/questions/35441124/parametrized-unit-tests-in-swift

标签

swift

unit-testing

parameterized-unit-test